Model A & B

Ford Garage

F-150 TOD Transmission Conversion

Tremec T170FT RTS

The 1984-87 Ford F-150 top shift overdrive (TOD) is a four speed manual transmission with fourth gear as an overdrive.

This overdrive transmission was made for Ford by Tremec, and it is known as a T170FT RTS. It was produced in three different overdrive ratios for use in Ford F-150 (and some limited F-250) full-size light-duty 2WD and 4WD pickup trucks.

This transmission has been a popular choice for Model A and early V8 Ford overdrive conversions, and a number of people have made complete kits available to do the conversion swap.

Ford Parts and Service Division
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
Top Shift Overdrive
Manufacturer: Tremec
Tremec Type: T170FT RTS
Remote Tower 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)
or equivalent
Notes: Case has no drain plug
RTS Remote Tower Shift
TOD Top Shift Overdrive

Tremec T170FT RTS TOD Specifications

The overdrive ratio of a Tremec RTS transmission can be identified by a sheet metal 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 tag should be 'RTS', and be immediately followed by a two-character alpha code as shown in Column 1 in the table below. The two-character alpha code will identify the overdrive ratio as originally built.

Beyond identifying the ratio, the numerous Tremec two-character alpha codes identify the original up-assembly as being for a 2WD or 4WD, and which speedometer drive gear they were equipped with. Other than identifying the OD ratio you have, the alpha code is unimportant in adapting the Tremec to the Model A or early V8 Ford.

Additionally, there is a Ford part number and a Tremec part number cast into the LH side of the aluminum case. The first style case is marked RF-E4TR-7006-AA and C-2604877, and the second style case is marked RF-E5TF-7006-AA and C-2605524.

For reference, the Transmission Code table below also shows the Ford part numbers and tooth counts of the various gears in each transmission configuration.

Specification compilation courtesy of Al Berry
Green-shaded cells indicate parts which are still generally available new in the aftermarket.
Transmission Codes % OD Ford and Tremec Part Numbers and Tooth Counts
Tremec Codes
T170FT ID Tag
Ford Code
VIN/GVWR/
Tire Label
Ratios Main Drive
Gear
(2 distinct)
Countershaft
(Cluster) Gear
(3 distinct)
1st
Gear
(1 shared)
2nd
Gear
(1 shared)
3rd
Gear
4th OD
Gear
(2 distinct)
RTS
AD, AE, AJ,
BJ, BP, BU,
BV*, BZ*, CS
*=obsoleted
B
(5.0L V8 /
302cid V8)
(4.9L L6 /
300cid L6)
27.6%
1st=3.2506
2nd=1.9213
3rd=1.0000
4th=0.7837
D8UZ-7017-A
E0TZ-7017-B
2604484
(8-7/8")
21T
D8UZ-7113-A
D0UZ-7113-A
2603740

32T
-35T-23T-15T
D9BZ-7A029-B
2604300


32T
E0TZ-7102-A
(2604232)
2605214

29T
Direct

E0TZ-7B340-B
2604242


18T
RTS
AA*, AF*, AH,
AK, BN, BR*,
BW
*=obsoleted

C
(5.8L V8 /
351cid V8)
37.9%
1st=3.0061
2nd=1.7766
3rd=1.0000
4th=0.7246
E0TZ-7017-C
2603806

(8-7/8")
22T
E0TZ-7113-B
2603243


31T
-35T-23T-15T
D9BZ-7A029-B
2604300


32T
E0TZ-7102-A
(2604232)
2605214

29T
Direct

E0TZ-7B340-B
2604242


18T
RTS
AB, AC, AG,
BM, BS, BT,
BY

D
(4.9L L6 /
300cid L6)
41.1%
1st=3.2506
2nd=1.9213
3rd=1.0000
4th=0.7087
D8UZ-7017-A
E0TZ-7017-B
2604484
(8-7/8")
21T
E0TZ-7113-A
2604234


32T-43T-23T-15T
D9BZ-7A029-B
2604300


32T
E0TZ-7102-A
(2604232)
2605214

29T
Direct

E0TZ-7B340-A
2605212


20T

IMO, the "Goldilocks" Tremec transmission for a Model A would be a combination of the the 1st and 2nd gear ratios of a Ford "Code C" transmission, combined with the 4th gear overdrive ratio of a "Code B" transmission.

Unfortunately, however, such a "combination" cannot be physically configured from the selection of component parts ever produced for the RTS. Refer to the Drivability and Suitability ~ Recommended Combinations section at the bottom of this web page for further explanation of why that configuration would theoretically be the "Goldilocks" solution.

The RTS/TOD transmission overdrive ratio as-built can also be identified by the Ford transmission code 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 below.

1987 F-150 2WD Regular Cab, Six Cylinder with Tremec 27.6% OD Code B

The transmission will be a Tremec T170FT RTS overdrive transmission if the label identifies the transmission as a code 'B' (27.6%), code 'C' (37.9%), or code 'D' (41.1%), respectively. This information is illustrated in Columns 2 and 3 in the table above.

1985 F-150 2WD Regular Cab Pickup

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 (4.750) inches. The fore-aft dimension between the flywheel housing contact surface and the transmission case mounting surface is 5-9/16 (5.5625) inches.

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 oil pan. Model AA and BB housings are not interchangeable with each other.

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.

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.
Modification to the Tremec transmission itself involves:

The Model AA throwout bearing hub, clutch release shaft, arm, and pressure plate are used, along with a 1949 Ford clutch disc. A Ford 8N-7550 clutch disc, 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.


Drivability Considerations

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

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

Any vehicle 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!

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.


Drivability and Suitability ~ Recommended Combinations

Blue-shaded attributes are shown for 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, and 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

(200cid L4)
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

(200cid L4)
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.
The taller 1st and 2nd gear ratios of the Model B (and early V8) transmissions improves the drivability and shift points greatly compared to that of the Model A transmission.
1931 Ruckstell
Dual High

(200cid L4)
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% 1st

(200cid L4)
2.71:1 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.
Synchronized 2nd and 3rd gears.
15% Taller 1st gear ratio is similar to Model B.
Mitchell Synchro
15% 1st & 2nd

(200cid L4)
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.
Four Speed
Transmission
Rev 1st 2nd 3rd 4th % OD Optimal Drivability and Suitability ~
Recommended Combinations and Usage Notes
Tremec
T170FT RTS

F-150 TOD
Code B


(5.0L V8 /
302cid V8)
(4.9L L6 /
300cid L6)
3.25:1 3.25:1 1.92:1 1:1 0.78:1 27.6%
  • 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.
Fully synchronized.
1st and 2nd gear ratios are similar to/worse than stock Model A.
4th gear (overdrive) ratio is more favorable for Model A and early V8 era Fords compared to code "C" and "D" transmissions.
Better suited for highway driving and/or underpowered engines.
Increased engine Torque and HP are highly recommended.
Tremec
T170FT RTS

F-150 TOD
Code C


(5.8L V8 /
351cid V8)
3.01:1 3.01:1 1.78:1 1:1 0.72:1 37.9%
  • 4.11 rear axle in a medium-light weight car with added power.
  • 3.78 rear axle in a light weight car with added power 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" transmissions.
Better suited for city driving.
Increased engine Torque and HP are required for highway driving.
Tremec
T170FT RTS

F-150 TOD
Code D


(4.9L L6 /
300cid L6)
3.25:1 3.25:1 1.92:1 1:1 0.71:1 41.1% Not Recommended - no benefits!
  • 4.11 rear axle in a light weight car and/or flat terrain.
Fully synchronized.
1st and 2nd gear ratios are similar to/worse than stock Model A.
4th gear (overdrive) ratio is very unfavorable for Model A and early V8 era Fords compared to code "B" and "C" transmissions.
Increased engine Torque and HP are required.
Blue-shaded attributes are shown for 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, and Red-shaded are the least desirable.

More related information on Ford Garage:

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

December 2017