Model A & B

Tremec T170FT RTS Four-Speed OD

3+1 Overdrive Transmission Conversion

Procure this book! Fifty-seven pages of detailed official 1984-87 Ford disassembly and reassembly photos, diagrams, description, and instructions specifically for RTS/TOD and RUG/SROD 3+1 Truck transmissions. The similar 1977 Ford Chassis Service Highlights publication covers the earlier iron case RUG-BP/SMOD 3+1 Car (and follow-on truck/van) transmissions. The 1979 Ford Chassis Service Highlights publication covers the 1979-83 aluminum RUG SROD 3+1 Car (and truck) transmissions.

The 1984-87 Ford RTS top shift overdrive transmission was made for Ford by Tremec, and it is known variously as a T170FT RTS 3+1 TOD. It was produced in three different overdrive ratios for use in Ford full-size light-duty 2WD and 4WD F-150 pickup trucks and Broncos.

With its cover-mounted cane shifter, the T170FT RTS 3+1 TOD transmission has been a popular choice for Model A and early V8 Ford overdrive transmission conversions, and a number of people have made complete kits available to do the transmission swap and conversion.

This Ford Garage page is the single most comprehensive, complete, and correct source of technical information on the RTS transmission and T170 family to be found on the web. If you have additional info, or potential corrections to contribute, please contact me by clicking my name at the bottom to initiate an email. Thank you!

Ford-Tremec T170 3+1 Family Variants

The Ford-Tremec T170 manual transmission family includes three types/variants of four-speed toploaders having the internal 'third' gear position configured as the top/overdrive gear ('fourth' to the driver). They are also known as 3+1 overdrives. The major visual differences are in the style of gear selection, and the case materials used.

In these transmissions, the overdrive (top gear) is actually in the 'third' gear internal position, and power is NOT directly transferred in-line through the input to the output shaft in top gear, unlike a conventional non-overdrive four-speed transmission.

Instead, the power in the T170 in overdrive operation is routed through the input main drive gear, into the cluster gear, back into the overdrive gear teeth on the main/output shaft, and then on to the universal joint. The countershaft and all bearings and the case are always under load and stress during overdrive.

The continuous offset loads on all the bearings, and on the main, cluster, and overdrive gears during overdrive operation is one reason that these 3+1 transmissions originally developed a somewhat poor reputation for robustness when abused, compared to that of the top gear loading in a planetary or conventional non-overdrive transmission.

The durability reputation of the 3+1 was especially aggravated by the many abusive pickup truck and van owners who were routinely towing heavy loads in overdrive, instead of in the direct drive (1:1) gear recommended by Ford.
In spite of this reputation, the aluminum-case T170FT RTS 3+1 transmission is robust enough in overdrive for the task at hand for usage in a Model A or Early V8 Ford.

The 1977-87 cast iron case T170F RUG 3+1 (aka SMOD) side-mounted external shifter variants were used in some 1977-78 cars (RUG-BP), 1978-79 pickup trucks (iron RUG-Cx), and 1978-87 vans (iron RUG-Cx). The T170F has a gate shifter lever and linkage (Hurst style) mounted externally on the iron tail shaft housing. None of the cast iron RUGs had a remote-mounted turret shifter housing, nor a case-mounted top shifter cover (cane shifter).

The iron RUG-BP tagged car transmission (specifically) has virtually no internal parts which are usable in an RTS 3+1 TOD, although the parts are visually quite similar.
However, the iron RUG-Cx tagged pickup truck and van transmissions are useful for parts for an RTS 3+1 TOD (re)build.

As an aside, the iron RUG 3+1 transmissions are similar in design and appearance to the earlier Ford 3.25" center distance (non-overdrive) HEH & RUG four-speed toploader performance transmissions of the 1960s-70s, and are sometimes visually mistaken for them.

The aluminum case T170FS RUG 3+1 SROD design variant was used in some 1979-83 cars as well as in 1980-83 trucks. It is a Single Rail Over Drive, having an enclosed rail tube and a remote-mounted turret shifter housing on the aluminum tail shaft extension. It does not have a case-mounted top shifter cover, nor an external case-mounted gate shifter linkage.

Some internal parts in the Truck (but not Car) aluminum RUG 3+1 SROD variants are usable in an RTS 3+1 TOD (re)build.

The 1984-87 aluminum case T170FT RTS 3+1 TOD design variant is a toploader transmission and was produced for 1984-87 F-150 pickups and Broncos, both 2WD and 4WD.

Only the RTS 3+1 TOD had a case-mounted aluminum top shifter cover with a cane shifter.

1984-87 Tremec T170FT RTS (TOD) Description

Ford Parts and Service Division
Ford Service Manual Description:

The top shift overdrive (TOD) is a four-speed manual transmission with fourth gear as an overdrive.

It is fully synchronized. All forward gears are helical-type and are in constant mesh. The forward gear changes are accomplished with synchronizer sleeves.

Reverse is provided through a reverse idler sliding gear which slides on a reverse idler gear. The reverse idler gear is in constant mesh with the countershaft gear. In reverse the spur-type gear on the reverse idler sliding gear meshes with the gear on the 1-2 synchronizer hub.

The top mounted shifter operates shift rails in the transmission cover assembly. The first-second fork and the reverse fork are attached directly to these rails.

The third and overdrive shift fork is attached to a shift rail which is mounted in the transmission case.

Third and overdrive are shifted by means of a shift pawl mounted on a rail in the transmission cover, contacting an overdrive shift control link in the transmission. This shift control link contacts the shift fork in the transmission.

A shift interlock system located in the transmission cover prevents the engagement of more than one gear at a time.

The transmission case, cover, and extension housing are aluminum. The mating surfaces of these components are sealed with Anaerobic Sealer (Gasket Eliminator).

OEM Application:	1984 - 1987 Ford F-150
Ford Type:	Four-Speed Manual TOD Topshift Over Drive
Manufacturer:	Tremec
Tremec Type:	T170FT RTS Remote Tower/Top Shift
Case Material:	Aluminum alloy
Fully Synchronized:	All forward gears are helical type in constant mesh
Lubricant:	3.5 US Pints 1.7 Liters SAE 80W D8DZ-19C547-A (ESP-M2C83-C) Driven 80W-90 GL4 or equivalent Do not use GL5 !
Notes:	Case has no drain plug
	No gaskets are used; Anaerobic sealer only
	TOD = Topshift Over Drive
	RTS = Remote Top Shift

The information published in the official Ford Parts and Service Division TOD and SROD Service Manual identifies three different gear ratio configurations offered in the Tremec T170FT RTS and the T170FS SROD series truck transmissions, and they are specified as 'B ratio', 'C ratio', and 'D ratio'.

'B' ratio = 27.6% overdrive (5.0L 302 V8, also some 4.9L 300 I6)
'C' ratio = 37.9% overdrive (5.8L 351 V8, also some 4.9L 300 I6)
'D' ratio = 41.1% overdrive (4.9L 300 I6)

These Ford ratio letters are utilized in Column 1 in the Transmission Specifications table below to organize the part gearing information of the three different RTS overdrive configurations.

1984-87 Tremec T170FT RTS 3+1 (TOD) Identification

There is both a Ford part number and a Tremec part number cast into the LH side of the aluminum RTS case. The first (1984) style case is marked RF-E4TR-7006-AA and C-2604877, and the second (1985-87) style case is marked RF-E5TR-7006-AA and C-2605524.

You may also find a similar four-speed 'RTS style' non-Jeep-input, top shift aluminum case transmission, but without Ford casting numbers or logo, and having only a Tremec case number C-2605275.

These 'RTS clones' were made by Tremec, but are not marked 'RTS' on the steel tag. I believe they may have been non-Ford replacement F-150 transmissions supplied by Tremec to aftermarket transmission shops. Anybody know different?

1985 F-150 2WD Regular Cab Pickup

1987 F-150 2WD Regular Cab, Six Cylinder with Tremec T170FT RTS transmission

When still in a vehicle, the Tremec RTS 3+1 (TOD) transmission can also be identified by the Ford transmission Type 'B' (Tremec OD) printed at the bottom center of the VIN/GVWR/Tire Information label (applied inside the drivers door opening) of a Ford F-150 pickup truck, as shown above.

The overdrive ratio of a Tremec RTS transmission can be identified by a steel tag which is riveted to the front RH side of the case. This is useful when evaluating a loose transmission at a junk yard or swap meet.

The first three characters on the Tremec tag will be 'RTS', and are immediately followed by a two-character alpha code as shown in the pic above, and in Column 1 in the table below.
The two-character alpha code identifies the overdrive ratio as originally built by Tremec.

Beyond identifying the OD ratio, the two-character alpha code following the 'RTS' identifies the original transmission assembly as being for a 2WD or 4WD, and identifies which speedometer drive gear it was originally equipped with (function of tire size and rear axle ratio combinations).

Other than identifying the specific transmission OD ratio, the RTS two-character alpha code is unimportant in adapting the T170FT to the Model A or early V8 Ford.

The various other codes stamped on the Tremec tag identify the production date, the Ford service designation number, and the Tremec unit serial number.

1984-87 Tremec T170FT RTS 3+1 (TOD) Specifications

The Transmission Specifications table below shows the Ford and aftermarket part numbers and tooth counts of the various gears in each RTS transmission configuration.

Peach-shaded cells indicate parts which are still generally available new in the aftermarket.

T170FT RTS 3+1 (TOD) Aluminum Top Shifter Transmission Codes	Ford, Tremec, and Aftermarket Part Numbers and Tooth Counts
Tremec Codes T170FT Steel ID Tag Alpha Codes	% OD Gear Ratios	Countershaft Cluster Gear (Input-4-2-1) (3 distinct)	Input Gear 1-1/16" Dia 10 spline (2 distinct)	3rd Gear Sleeve	4th OD Gear (2 distinct)	2nd Gear (1 common)	1st Gear (1 common)
'D ratio' RTS- AB, AC, AG, BM, BS, BT, BY 84-87 F-150/Bronco 4.9L 300 I6 good for case, shifter top, input gear/shaft, 1 & 2 gears, reverse gears, synchro hubs, output shaft (can be converted to RTS 'B ratio' using 27.6% RUG 3+1 cluster and OD gears)	'D' ratio 41.1% 1st=3.2508 2nd=1.9213 3rd=1.0000 4th=0.7087	32-43-23-15 E0TZ-7113-A 2604234 T170-8H (convert RTS 'D' to 'B' ratio using RUG 3+1 T170-8C gear)	21T E0TZ-7017-B 2604484 T170-16N 8-7/8" long (interchanges w/ RUG 3+1)	3rd Direct	20T E0TZ-7B340-A 2605212 T170-11H 1G central 2-21/64" diameter (convert RTS 'D' to 'B' ratio using RUG 3+1 T170-11C gear)	29T E0TZ-7102-A (2604232) 2605214 T170-21F 3-53/64" diameter	32T D9BZ-7A029-B 2604300 J8132389 T170-12B 4-36/64" diameter
'B ratio' RTS- AD, AE, AJ, BJ, BP, BU, BV, BZ, CS 84-87 F-150/Bronco 4.9L 300 I6 5.0L 302 V8	'B' ratio 27.6% 1st=3.2508 2nd=1.9213 3rd=1.0000 4th=0.7837	32-35-23-15 D8UZ-7113-A 2603740 T170-8C 1G central 15?	21T E0TZ-7017-B 2604484 T170-16N 8-7/8" long (interchanges w/ RUG 3+1)	3rd Direct	18T E0TZ-7B340-B 2604242 T170-11J (interchanges w/ RUG 3+1)	29T E0TZ-7102-A (2604232) 2605214 T170-21F 3-53/64" diameter	32T D9BZ-7A029-B 2604300 J8132389 T170-12B 4-36/64" diameter
'C ratio' RTS- AA, AF, AH, AK, BN, BR, BW 84-87 F-150/Bronco 4.9L 300 I6 5.8L 351 V8	'C' ratio 37.9% 1st=3.0061 2nd=1.7767 3rd=1.0000 4th=0.7247	31-35-23-15 E0TZ-7113-B 2603243 T170-8J	22T E0TZ-7017-C 2603806 T170-16P 8-7/8" long 2G equal (interchanges w/ RUG 3+1)	3rd Direct	18T E0TZ-7B340-B 2604242 T170-11J 1G forward (interchanges w/ RUG 3+1)	29T E0TZ-7102-A (2604232) 2605214 T170-21F 0G 3-53/64" diameter	32T D9BZ-7A029-B 2604300 J8132389 T170-12B 2G central 4-36/64" diameter

IMO, the "Goldilocks" Tremec RTS transmission for a Model A or Model B is the combination of the the 1st and 2nd gear ratios of a Ford RTS 'C ratio' transmission, combined with the 4th gear overdrive ratio of an RTS 'B ratio' transmission. Refer below for the necessary RUG 3+1 parts to swap into an RTS case to accomplish this.

Refer to the Drivability and Suitability ~ Recommended Combinations section further down this page for explanation of why that configuration would theoretically be the "Goldilocks" transmission for an early Ford conversion.

Earlier Tremec T170F RUG 3+1 (SMOD), and T170FS RUG 3+1 (SROD) Specifications

Peach-shaded cells indicate parts which are still generally available new in the aftermarket.

T170F RUG 3+1 (SMOD) Iron Side Shifter Transmission Codes	% OD Gear Ratios	Countershaft Cluster Gear (Input-4-2-1)	Input Gear 1-1/16" Dia 10 spline	3rd Gear Sleeve	4th OD Gear	2nd Gear	1st Gear
D7DR-7006-AA 2603606 case* 2602885 retainer, (T160-6G) *209/307 bearings Orion RUG BP Ford RUG BP 77-78 Granada/Monarch 3.3L 200 I6	23.6% 1st=3.2889 2nd=1.8381 3rd=1.0000 4th=0.8094	37-40-26-15 D7DZ-7113-A 2603885 T170-8B	24T D7DZ-7017-A 2603596 T170-16E 8-7/8" long	3rd Direct	21T D7DZ-7B340-A 2603884 T170-11B 2-32/64" diameter	31T D7DZ-7102-A 2603612 T170-21B 3-50/64" ? diameter	32T D9BZ-7A029-B 2604300 J8132389 T170-12B 4-36/64" diameter
D7DR-7006-AA 2603606 case 2603718 retainer 308/308 bearings with input spacer ring Orion RUG CB Ford RUG CB D8TR-KA 78-79 F-150 Orion RUG CD D8TR-MA 78-79 F-150 4.9L 300 I6 5.0L 302 V8 Orion RUG CL Ford RUG CL D8UR-EA 78-87 Econoline 4.9L 300 I6	27.6% 1st=3.2508 2nd=1.9213 3rd=1.0000 4th=0.7837	32-35-23-15 D8UZ-7113-A 2603740 T170-8C (to convert RTS 'D ratio' into RTS 'B ratio')	21T D8UZ-7017-A 2604484 T170-16F 8-7/8" long 2G central (interchanges w/ RTS)	3rd Direct	18T D8UZ-7B340-A 2603737 T170-11C 2G wide (to convert RTS 'D ratio' into RTS 'B ratio') 2-29/64" diameter	29T D8UZ-7102-A 2603738 T170-21C 2G wide (iron case, interchange w/ RTS?) 3-53/64" diameter	32T D9BZ-7A029-B 2604300 J8132389 T170-12B 0G (interchanges w/ RTS) 4-36/64" diameter
D7DR-7006-AA 2603606 Goldilocks Gearing Taller 1-2 gears Favorable 2-3 gap plus 27% OD (not originally configured in RTS case) 78-87 Econoline 78-79 F-150 5.8L 351 V8	27.0% 1st=3.0061 2nd=1.7767 3rd=1.0000 4th=0.7874	31-34-23-15 D8UZ-7113-B 2603745 T170-8D 1G central 34?	22T D8UZ-7017-B 2603806 T170-16G 8-7/8" long 1G central (interchange w/ RTS?)	3rd Direct	19T D8UZ-7B340-B 2603744 T170-11D 1G central 3G even? (interchange w/ RTS?) 2-37/64" diameter	29T D8UZ-7102-A 2603738 T170-21C 2G wide (iron case, interchange w/ RTS?) 3-53/64" diameter	32T D9BZ-7A029-B 2604300 J8132389 T170-12B 0G (interchanges w/ RTS) 4-36/64" diameter

T170FS RUG 3+1 (SROD) Aluminum Turret Shifter Transmission Codes	% OD Gear Ratios	Countershaft Cluster Gear (Input-4-2-1)	Input Gear 1-1/16" Dia 10 spline	3rd Gear Sleeve	4th OD Gear	2nd Gear	1st Gear
D9BR-7006-AB 2604194 case casting RUG DB, E0TR-BA RUG DC, E0TR-BA, 351, 21T input? RUG DE, E0ZR-EA, mustang? RUG DG, E1TR-AA RUG DH, E1TR-BA, 351 RUG DL, E1TR-CA RUG DN, E1TR-DA RUG DP, E1TR-EA RUG DR, E1TR-AB RUG DS, E1TR-BB, 351 RUG DT, E1TR-CB RUG DU, E1TR-GA RUG DV, E1TR-HA, 21T input? RUG DY, E1TR-JA RUG DZ, E1TR-KA RUG EF, E1TR-SA 2WD F150 RUG EJ, 21T input? RUG EM, E2ZR-AA RUG EW, 21T input? RUG FD, 80-83 2WD F150 RUG FE, 81-83 4WD F150? RUG FM, 21T input? RUG FN, 21T input?
1979-83 Car Aluminum SROD Transmissions ~ Uses 209/307 Bearings
79-83 Fairmont/Zephyr 3.3L 200 I6	23.6% 1st=3.2889 2nd=1.8381 3rd=1.0000 4th=0.8094	37-40-26-15 D9BZ-7113-A 2604182 T170-8F	24T D9BZ-7017-A 2603827 T170-16H 9-5/8" long	3rd Direct	21T D9BZ-7B340-A 2604181 T170-11F 2-33/64" diameter	31T D9BZ-7102-A 2603894 T170-21E 3-50/64" diameter	32T D9BZ-7A029-B 2604300 J8132389 T170-12B 4-36/64" diameter
79-83 Fairmont/Zephyr 5.0L 302 V8	35.6% 1st=3.0720 2nd=1.7169 3rd=1.0000 4th=0.7376	36-41-26-15 D9BZ-7113-B 2603927 T170-8G	25T D9BZ-7017-B 2603926 T170-16J 9-5/8" long	3rd Direct	20T D9BZ-7B340-B 2603924 T170-11G 2-26/64" diameter	31T D9BZ-7102-A 2603894 T170-21E 3-50/64" diameter	32T D9BZ-7A029-B 2604300 J8132389 T170-12B 4-36/64" diameter
79-83 Granada/Monarch 4.1L 250 I6	23.6% 1st=3.2889 2nd=1.8381 3rd=1.0000 4th=0.8094	37-40-26-15 D9BZ-7113-A 2604182 T170-8F	24T D9DZ-7017-A 2603899 T170-16K 8-7/8" long	3rd Direct	21T D9BZ-7B340-A 2604181 T170-11F 2-33/64" diameter	31T D9BZ-7102-A 2603894 T170-21E 3-50/64" diameter	32T D9BZ-7A029-B 2604300 J8132389 T170-12B 4-36/64" diameter
79-83 Granada/Monarch 5.0L 302 V8	35.6% 1st=3.0720 2nd=1.7169 3rd=1.0000 4th=0.7376	36-41-26-15 D9BZ-7113-B 2603927 T170-8G	25T D9DZ-7017-B 2603925 T170-16L 8-7/8" long	3rd Direct	20T D9BZ-7B340-B 2603924 T170-11G 2-26/64" diameter	31T D9BZ-7102-A 2603894 T170-21E 3-50/64" diameter	32T D9BZ-7A029-B 2604300 J8132389 T170-12B 4-36/64" diameter
RUG DA 79-83 Mustang/Capri Hydraulic clutch 4.1L 250 I6	23.6% 1st=3.2889 2nd=1.8381 3rd=1.0000 4th=0.8094	37-40-26-15 D9BZ-7113-A 2604182 T170-8F	24T D9ZZ-7017-A 2603898 T170-16M 11-1/16" long	3rd Direct	21T D9BZ-7B340-A 2604181 T170-11F 2-33/64" diameter	31T D9BZ-7102-A 2603894 T170-21E 3-50/64" diameter	32T D9BZ-7A029-B 2604300 J8132389 T170-12B 4-36/64" diameter
RUG CS RUG EM 79-83 Mustang/Capri 5.0L 302 V8	35.6% 1st=3.0720 2nd=1.7169 3rd=1.0000 4th=0.7376		20T? 209 bearing ?" long	3rd Direct
1980-83 Truck Aluminum SROD Transmissions ~ Uses 308/308 Bearings, with input main drive gear bearing spacer ring
RUG DB E0TR-AB, 2WD 80-83 F-150 4.9L 300 I6	'D' ratio 41.1% 1st=3.2508 2nd=1.9213 3rd=1.0000 4th=0.7087	32-43-23-15 E0TZ-7113-A 2604234 T170-8H	21T E0TZ-7017-B 2604484 T170-16N 8-7/8" long	3rd Direct	20T E0TZ-7B340-A 2605212 T170-11H 1G rearward 2-21/64"	29T E0TZ-7102-A (2604232) 2605214 T170-21F 3-53/64" diameter	32T D9BZ-7A029-B 2604300 J8132389 T170-12B 4-36/64" diameter
RUG EL E2TR-FA 80-83 F-150 5.0L 302 V8 4.9L 300 I6	'B' ratio 27.6% 1st=3.2508 2nd=1.9213 3rd=1.0000 4th=0.7837	32-35-23-15 D8UZ-7113-A 2603740 T170-8C	21T E0TZ-7017-B 2604484 T170-16N 8-7/8" long	3rd Direct	18T E0TZ-7B340-B 2604242 T170-11J	29T E0TZ-7102-A (2604232) 2605214 T170-21F 3-53/64" diameter	32T D9BZ-7A029-B 2604300 J8132389 T170-12B 4-36/64" diameter
80-83 F-150 5.8L 351 V8	'C' ratio 37.9% 1st=3.0061 2nd=1.7767 3rd=1.0000 4th=0.7247	31-35-23-15 E0TZ-7113-B 2603243 T170-8J	22T E0TZ-7017-C 2603806 T170-16P 8-7/8" long	3rd Direct	18T E0TZ-7B340-B 2604242 T170-11J	29T E0TZ-7102-A (2604232) 2605214 T170-21F 3-53/64" diameter	32T D9BZ-7A029-B 2604300 J8132389 T170-12B 4-36/64" diameter
Peach-shaded cells indicate parts which are still generally available new in the aftermarket.
RTS 3+1 Component Parts			Part Numbers
RTS Aluminum Main Case Face-to-Input Nose 6-7/16" Case-to-Retainer Nose 3-21/32"			T170-1F E4TZ-7005-B C-2604877 C-2605524
Front Bearing Retainer Overall Length 3-13/16” Outside Diameter 1-7/16" For 1-1/16" input shaft Retainer OD 4.850"			T170-6C 2605314 CI RTS E4TZ-7050-A CI RTS w/ pry notches 2603718 CI RUG 3+1 D8UZ-7050A CI RUG 3+1 w/o pry notches E0TZ-7050-A AL SROD 326724A RF-E0TR-7050-AA AL SROD C2604224-1B
Main Drive (Input) Gear Ball Bearing Main (output) Shaft Ball Bearing 2.5mm input spacer ring			308L4 40mm ID x 90mm OD x 23mm Wide, w/ lock ring Ford D8OZ-7025-A KOYO 83763-1 KOYO 83763-3 Ford D8UZ-7025-A Ford E3TZ-7025-D Ford E5TZ-7025-C KOYO NU308C3 743202-L4 MRC 308 SZZG double shield 6308 2RSNR double seal SKF 6308 2RS1NR double seal
Input Shaft Oil Seal			CR/SKF 11111 CR/SKF 11123 D8UZ-7A283-B E3FZ-7A011-A National 3638 Victor Dana 45820
Input Shaft Cylindrical Roller Bearings 15 required			C417Q BCA Federal Mogul
Main (output) Shaft 2WD (23-11/32") 32-37-28 Spline			T170-2K E0TZ-7061-C 2604483
Main (output) Shaft 4WD (19-11/32") 32-37-31 Spline			T170-2M E1TZ-7061-C 2604466
Counter Shaft (7/8" diameter, 10-1/8" long)			WT296-3 2602657
Counter Shaft Cylindrical Roller Bearings 42 required			QAR33724 BCA Federal Mogul C1086Q
Reverse Idler Shaft			WT296-35 2602658
Reverse Idler Cylindrical Roller Bearings 44 required			C407Q BCA Federal Mogul
Reverse Idler Gear 16T 25 Splines 3-17/32" long			T170-10B 2603617 8132399 D7DZ-7141-A
Reverse Idler Sliding Gear 19 Spur Tooth			T170-10C WT296-10C 2605066 8132402 D9BZ-7D223-A
1-2 Synchro Sleeve w/ Mainshaft Reverse Gear 22 Spur Tooth			WT296-81 2605139
1-2 Synchro Hub & Sleeve Asm (long keys)			1AT170-80B 2670167
3-4 Synchro Hub & Slider Asm (short keys)			1AT170-2.5B
1-2 Fork			T170-23E
3-4 Fork			T170-23F
Reverse Fork			T170-23G
RTS Shift Lever Steel Cap			E4TZ-7220-A
Iron RUG 3+1 Cluster Gear 32-35-23-15T Use w/ T170-11C, 18T Overdrive Gear from a 1978-87 Iron RUG CB, CD, or CL to convert an RTS 'D ratio' from 41.1% to 27.6% OD, or for use as a replacement gear in an existing 27.6% RTS 'B ratio'			T170-8C D8UZ-7113-A 2603740
Iron RUG 3+1 4th Gear (OD) 18T Use w/ T170-8C, 32-35-23-15 Cluster Gear from a 1978-87 Iron RUG CB, CD, or CL to convert an RTS 'D ratio' from 41.1% to 27.6% OD, or for use as a replacement gear in an existing 27.6% RTS 'B ratio'			T170-11C D8UZ-7B340-A 2603737
41.1% RTS 'D ratio' AB 2WD AC AG BM BS 2WD BT 4WD BY 27.6% RTS 'B ratio' AD AE AJ BJ BP BU 2WD BV 2WD BZ 4WD CS 37.9% RTS 'C ratio' AF AA AH 4WD AK 2WD BN BR BW			E4TR BA E6TR JA E6TR KA E4TR JA E6TR LA E6TR MA E6TR RA E4TR HA E4TR NA

Drivability Considerations ~ Torque and Power

Overdrives are a Physics problem, not just a Mathematics problem!

Increased Torque and HP at the right RPM are required to go faster at lower engine RPM, not just mechanical overdrive gear ratios!

Any Model A or B Ford would benefit from the added engine torque and horsepower of a 5.5 or greater compression ratio cylinder head and a Stipe IB330 camshaft.

Essentially, top vehicle speed will occur when aerodynamic drag equals power output.
Proper gearing keeps the engine RPM in the useful range between "just below max torque" to “around max power” for all road speeds.

Stock Model A Torque and Horsepower Curves

Improper gearing results in lugging the engine at low RPMs and destroying Babbitt engine bearings!

Lugging occurs when the engine is operated under load at below peak torque for any length of time.

Also, don't forget to improve your brakes!

Drivability and Suitability ~ Recommended Combinations

Highlighted below are the relative drivability improvements of various transmission gearings compared to the stock Model A gearing. Assumptions are based on stock tire sizes and engine configuration.

Blue-shaded attributes are equivalent to the stock Model A.
Green-shaded transmissions, ratios, and attributes are preferred for improved drivability compared to stock Model A.
Yellow-shaded attributes are questionable.
Violet/Red-shaded are the least desirable.

Three Speed Transmission	Rev	1st	2nd	3rd	4th	% OD	Optimal Drivability and Suitability ~ Recommended Combinations and Usage Notes
Stock Model A 1928-31	3.745:1	3.12:1	1.85:1	1:1	~	~	4.11 rear axle in a heavy-medium weight car and/or hill terrain. 3.78 rear axle in a medium-light weight car. 3.54 rear axle in a light weight car and/or flat terrain.
Stock Model B 1932-34	3.383:1	2.820:1	1.604:1	1:1	~	~	4.11 rear axle in a heavy-medium weight car and/or hill terrain. 3.78 rear axle in a medium-light weight car. Synchronized 2nd and 3rd gears. 15% Taller 1st and 2nd gear ratios are similar to Model B. When coupled with a 28% Mitchell driveshaft overdrive unit (or 33% OD unit with a 4.11:1 axle), this transmission approaches the "Goldilocks" solution for both low speed and high speed drivability, though without a transmission overdrive gear. CON: Significant added OD mass on torque tube. CON: Extra OD shift lever on floorboard.
1931 Ruckstell Dual High		2.50:1	1.00:1	0.80:1	~	25%	4.11 rear axle in a heavy-medium weight car and/or hill terrain. 3.78 rear axle in a medium-light weight car. 1st gear ratio is even taller than Model B. 2nd gear ratio is direct, 1:1. 3rd gear ratio is a 25% overdrive, not 1:1. Increased engine Torque and HP are highly recommended.
Mitchell Synchro 15% 2nd only Model A		3:12:1	1.61:1	1:1	~	~	4.11 rear axle in a heavy-medium weight car and/or hill terrain. 3.78 rear axle in a medium-light weight car. Synchronized 2nd and 3rd gears. 15% Taller 2nd gear ratio is similar to Model B. CON: No improvement in 1st gear ratio.
Mitchell Synchro 15% 1st & 2nd Model A		2.71:1	1.61:1	1:1	~	~	4.11 rear axle in a heavy-medium weight car and/or hill terrain. 3.78 rear axle in a medium-light weight car. Synchronized 2nd and 3rd gears. 15% Taller 1st and 2nd gear ratios are similar to Model B. When coupled with a 28% Mitchell driveshaft overdrive unit (or 33% OD unit with a 4.11:1 axle), this transmission approaches the "Goldilocks" solution for both low speed and high speed drivability, though without a transmission overdrive gear. CON: Significant added OD mass on torque tube. CON: Extra OD shift lever on floorboard.

3+1 Overdrive Transmission	Rev	1st	2nd	3rd	4th	% OD	Optimal Drivability and Suitability ~ Recommended Combinations and Usage Notes
Stock Model A 1928-31	3.75:1	3.12:1	1.85:1	1:1	~	~	BASELINE REFERENCE - Stock tire sizes and engine configuration
Stock Model B 1932-34	3.38:1	2.820:1	1.604:1	1:1	~	~	BASELINE REFERENCE - Stock tire sizes and engine configuration
RTS 'C ratio' 37.9% Tremec T170FT RTS F-150 TOD	3.01:1	3.01:1	1.78:1	1:1	0.72:1	37.9%	4.11 rear axle in a heavy-medium weight car with added power and/or flat terrain. 3.78 rear axle in a medium-light weight car with added power and/or flat terrain. 3.54 rear axle in a light weight car and/or flat terrain. Fully synchronized. Taller 1st and 2nd gear ratios are much more favorable compared to stock Model A. 4th gear (overdrive) ratio is less favorable for Model A and early V8 era Fords compared to code 'B ratio' transmissions. Better suited for city driving and general driveability. Increased engine Torque and HP are highly recommended for highway driving.
Goldilocks Gearing 27.0% T170F RUG 3+1 gears in a T170FT RTS case	3.01:1	3.01:1	1.78:1	1:1	0.79:1	27.0%	For Model A and Early V8 Ford. (never originally configured in a F-150 T170FT RTS case by Ford/Tremec). See Specification Table at top of page for exact RUG 3+1 parts required to configure. 4.11 rear axle in a heavy-medium weight car and/or hill terrain. 3.78 rear axle in a medium-light weight car. 3.54 rear axle in a light weight car and/or flat terrain. Best suited for both city and highway driving, and across a range of weights and terrain. Increased engine Torque and HP are recommended.
RTS 'B ratio' 27.6% Tremec T170FT RTS F-150 TOD	3.25:1	3.25:1	1.92:1	1:1	0.78:1	27.6%	3.78 rear axle in a medium-light weight car. 3.54 rear axle in a light weight car and/or flat terrain. 3.27 rear axle in a light weight car and/or flat terrain. Fully synchronized. 1st and 2nd gear ratios are worse than stock Model A. 2nd to 3rd gear gap is worse than stock Model A. 4th gear (overdrive) ratio is more favorable for Model A and early V8 era Fords compared to 'C ratio' and 'D ratio' transmissions. Better suited for highway driving and/or underpowered engines. Increased engine Torque and HP are recommended.
RTS 'D ratio' 41.1% Tremec T170FT RTS F-150 TOD	3.25:1	3.25:1	1.92:1	1:1	0.71:1	41.1%	Not Recommended - no benefits for most cars! 4.11 rear axle in a medium-light weight car. Bad 1-2, 2-3 shifts. 3.78 rear axle in a light weight car and/or flat terrain. Poor 1-2, 2-3 shifts. Poor 4th gear ratio. 3.54 rear axle in a light weight car and/or flat terrain. Bad 4th gear ratio. 3.27 rear axle in a light weight car and/or flat terrain. Bad 4th gear ratio. Fully synchronized. 1st and 2nd gear ratios are worse than stock Model A. 2nd to 3rd gear gap is worse than stock Model A. 4th gear (overdrive) ratio is very unfavorable for Model A and early V8 era Fords compared to 'B ratio' and 'C ratio' transmissions. Increased engine Torque and HP are required for highway driving.
	Rev	1st	2nd	3rd	4th	% OD

Conversion and Installation Considerations

It is recommended to use the Model AA truck four-speed transmission clutch (bell) housing rather than the Model A three-speed transmission clutch housing as the basis for the conversion.

The 1929-31 Model AA truck clutch housing is shorter fore-aft than a Model A three-speed housing, and its use requires less (if any) modification to the frame center crossmember for clearance to the transmission and U-Joint covers.

Both the Model AA and BB truck clutch housings have the same critical dimensions.
The inside diameter of the opening for the transmission front drive gear retainer is 4-3/4 inches (4.750").
The fore-aft dimension between the flywheel housing contact surface and the transmission case mounting surface is 5-9/16 inches (5.5625").

The Model BB clutch housing does not have any front radius rod (wishbone) mounting provisions compared to a Model AA housing, but the BB housing is necessary when using a Model B/BB flywheel housing and uncut Model B oil pan. Model AA and BB flywheel and clutch housings are not interchangeable with each other. They must be paired along with the corresponding oil pan.

Use of either the Model AA or BB clutch housing does however require fabrication of brake and clutch pedal mounting provisions. A provision for mounting the emergency brake handle to the transmission must also be fabricated.

The shift lever opening position in the floorboard and mat is slightly affected, moving rearward from the stock Model A position.

The Model AA throwout bearing hub, clutch release shaft, arm, and pressure plate are used.a 1949 Ford clutch disc. A Ford 8N-7550 clutch disc,
A C5NN-7600 pilot bearing and C0NN-7580-A throwout bearing can also be used.

Alternatively, a 9 inch diaphragm pressure plate and matching clutch driven disc for a 1983-88 Ford Thunderbird or 1984-86 Mustang SVO 2.3L turbocharged four cylinder can be mounted to a lightened and faced Model A or B flywheel by drilling and tapping six additional holes. The Thunderbird's 9 inch clutch disc hub has the same 1-1/16 inch x 10 spline as the Tremec RTS input shaft.

The system conversion based on the Model AA clutch housing also requires the shortening of the Model A torque tube, drive shaft, and rear radius rods approximately 1-1/2 inches.

To provide clearance to the crossmember flange at center, cut off the top center bolt hole tabs on the inner and outer Model A universal joint upper clamshells, or alternatively, use the early V8 era four-bolt clamshells. Design the hole pattern in the rear main bearing retainer for the chosen clamshell design.

Modification to the Tremec transmission itself involves:

Drilling and tapping the front of the case for the Model AA clutch housing attaching bolt locations.
Reduction of the front main bearing retainer outside diameter size to fit the Model AA clutch housing bore (4.750 inches)
(for reference, the stock Tremec retainer outside diameter is 4.850 inches, and the throwout diameter is 1.430 inches)
Enlargement/sleeving of the front main bearing retainer diameter to match the AA throwout bearing hub.
Shortening of the (main drive gear) input shaft pilot nose length by about 5/8 inches, and removal of about 1/4 inch of spline length from the front of the shaft.
Replacement of the tail shaft extension with a suitable rear bearing retainer adaptor plate.
(for reference, the stock Model A rear bearing retainer thickness is 1-5/16 inches (1.3125") between the gasket mounting surfaces.)
Shortening, splining, drilling and tapping of the rear of the transmission output (main) shaft for mounting the Model A universal joint.
Adaptation of the shift lever to suit the user's needs. A 1980-86 Jeep T176 one-piece cane shift lever can be easily adapted to replace the Ford stub shifter shaft. Search for Crown Automotive 5359835 shift lever.
A very nice 1-7/8" diameter black engraved 4 speed shift knob (3/8"-16) is available from core-shifters.com to fit the Jeep lever.

Disassemby and Reassembly Tools

Because of the unique internal design, construction, and gear diameters of the RUG 3+1 and RTS overdrives, neither the input nor output shaft can readily be removed from the case without first pulling the ball bearings from the shafts and case. The opposite sequence is necessary for reassembly. Special Ford service tools were made in order to accomplish this while the trans was on the bench.

Even after removing the bearings there are a number of steps in particular sequence necessary to get the case emptied and the entire transmission apart. It is not as easy or straightforward as working on a conventional four speed performance toploader of the 1960s-70s.

Ford Rotunda/OTC Essential Service Tools for Toploader Transmissions
Number	Bold-on-Green shaded tool numbers are useful for RTS
T57L-500-B	Bench Mounted Holding Fixture
T64P-7111-A	Dummy Countershaft Tool
T64P-7140-A	Dummy Reverse Idler Shaft Tool (4") (RAB, RAN, RUG)
T75L-7025-A	Transmission Bearing Service Set
T75L-7025-B	Remover/Replacer Tube (Short) (308-024) (RTS Input Shaft Bearing Remove/Install)
T75L-7025-C	Remover/Replacer Tube (Long) (308-025) (RTS Output Shaft Bearing Remove/Install)
T75L-7025-D	Bearing Collet (2), Car-Large (HEH, RUG, RUG-BP Output, 35/80/21mm 307 size)
T75L-7025-E	Bearing Collet (2), Car-Small (Output, 35/72/17mm 207 size)
T75L-7025-F	Bearing Collet (2), Truck (RUG-Cx 3+1, RTS, SROD, 40/90/23mm 308 size)
T75L-7025-G	Bearing Collet Sleeve (Car) (308-029) (HEH, RUG, RUG-BP Output) (207/307 size)
T75L-7025-H	Bearing Collet Sleeve (Truck) (308-030?) (RUG-Cx 3+1, RTS, SROD) (209, 308 size)
T75L-7025-J	Forcing Screw (15/16"-12 x 8-3/8") (RUG 3+1, RTS Input Shaft Remove; 2WD Output Shaft Remove)
T75L-7025-K	Bearing Shaft Collar Installer (308-031) (RTS Input/Output Shaft Bearing Install)
T75L-7025-L	Threaded Shaft Adaptor (308-032) (Internal/External Threaded) (for RTS w/ Model A U-Joint Splines)
T75L-7025-M	Bearing Shaft Collar Installer (308-033) (0.960" ID Ranger M5OD-R1)
T75L-7025-N	Bearing Shaft Collar Installer (308-034) (0.812" ID Ranger RAD)
T75L-7025-P	Bearing Shaft Collar Installer (308-035) (1.065" ID RTS 2WD Output Shaft Bearing Install; Ranger M5OD)
T75L-7025-Q	Replacer Dummy Bearing (308-036) (Borg Warner T-18, T-19; 35/40mm ID, 72/90mm OD)
T75L-7025-R	Bearing Shaft Collar Installer (308-037) (Borg Warner T-18, T-19)
T75L-7025-S	Bearing Shaft Collar Installer (308-038) (Borg Warner T-18, T-19)
T77F-7050-A	Seal Installer (Input Bearing Retainer)
T77F-7050-B	Seal Remover (Input Bearing Retainer)
T77L-7025-A	Bearing Collet (2), (3.3465 OD) (308-065) (HEH, RUG, RUG-BP Input, 45/85/19mm 209 size)
T77L-7025-B	Dummy Bearing (308-066) (HEH, RUG, RUG-BP Output 35/80/21mm 307 size)
T77L-7025-C	Remover/Replacer Tube (Short) (308-067) (RUG 3+1, RTS, SROD Input Shaft Bearing Install)
T77L-7025-D	Shaft Clamp (308-068) (RUG 3+1, RTS, SROD Input Shaft Bearing Install)
T77L-7025-F	Transmission Bearing Service Set (RUG-BP)
T84T-7025-A	Bearing Replacer (308-091) (RTS 4WD Output Shaft Bearing Install)
T84T-7025-B	Forcing Screw (15/16"-12 x 11.5") (308-092) (RTS 4WD Output Shaft Bearing Remove)
Fabricate	Bearing Installer ~ Double-Stud Adaptor (for modified RTS Output Shaft with Model A U-Joint Splines) (use with T75L-7025-L and T75L-7025-B )
Fabricate	Alternate Bearing Installer ~ Heavy Bushing (for modified RTS Output Shaft with Model A U-Joint Splines) (use with T75L-7025-K, T75L-7025-R, T75L-7025-B, and hex bolt )
Fabricate	Bearing Remover ~ Button-Head Centering Stud (for modified RTS Output Shaft with Model A U-Joint Splines) (use with T75L-7025-F, T75L-7025-B, and T84T-7025-B)
Fabricate	Alternate Bearing Remover ~ Hex Bolt Centering Stud (for modified RTS Output Shaft with Model A U-Joint Splines) (use with T75L-7025-F, T75L-7025-B, and T84T-7025-B)
Purchase	Pry Bar, Pin Punch, Hammer, Snap Ring Pliers, 1/2" & 5/8" Tools, Chain Wrench for Shift Lever Cap

More related information on Ford Garage:

For more Model A & B related information, use the Site Search box at the top or bottom of this page.
Model A Ruckstell Dual High Transmission
Model A Mitchell Synchronized Transmission
Model A & B Rear Axle Gear Ratios
Model AA Four-Speed Transmission Clutch Housing

December 2017