The Borg-Warner T90 was a common transmission found in 1946-1971 Jeeps. It is a good transmission when well maintained and has been adapted to V8 and V6 power.
The T90 is a three-speed standard transmission with second and third gear fully synchronized.
There were three versions of this transmission:
T90A1 – This version was used from 1946-1962 behind the “Go Devil” four-cylinder head and had a 7″ input shaft stick-out length with 15/16″ x 10 splines.
T90C – This version was used from 1963-1971 with the “Hurricane” four-cylinder engine. It has a 7″ input shaft stick-out length with 15/16″ x 10 splines. The case of the T90C is actually marked T90A. The only way to know if you have the T90C transmission is to confirm it came out of a post-1962 Jeep or pull the top cover and count the gears.
T90J – This version was used with six-cylinder trucks from 1952-1965. It has a 9.25″ input shaft stick-out length with 1.125″ x 10 splines.
All 4WD T90 transmissions have a 1.375″ x 6 spline output shaft. A 2WD version of the T90 was made, but is a rarity.
The factory service manual called for changing the transmission fluid every 12,000 miles with SAE 90W or 80W GL4 fluid. It is OK to use 80W-90 fluid, just be sure to not use any fluid labeled “Severe” and ensure the fluid is safe for brass synchros. Avoid GL5 gear oil.
Gear Ratios
| Gear | T90A/T90J | T90C |
|---|---|---|
| Reverse | 3.79 | 4.53 |
| 1st Gear | 2.79 | 3.34 |
| 2nd Gear | 1.55 | 1.85 |
| 3rd Gear | 1.00 | 1.00 |
Fluid Type and Capacity
| Lubricant | SAE 90W GL4 SAE 80W GL4 |
| Capacity | 1.25 qts (1.18L) |
Other Specifications
| Weight | 75lbs |
| Length | 8.80″ |
| Height | 14″ |
| Input Splines | 10 |
| Output Splines | 6 |
| Pilot Tip Width | unknown |
Transfer Case Compatibility
The Jeep T90 came factory with the Jeep Dana Spicer Model 18 transfer case, and only the small input bore versions.
T90 was available attached to the Dana 20 in the 1962-1965 J Series trucks.
It is possible to join a T90 to the Dana Spicer Model 20 transfer case using the Novak kit here.
Engine/Bellhousing Compatibility
GM – Buick V6, Chevy Small Block V6 and V8 conversions are done with this transmission. The GM adapter can be found made by Novak here.
Ford – The T90 transmission is adaptable to Ford Pinto, Mustang II, Rangers, and other Ford Inline-4 engines. An adapter can be found made by Novak here.
AMC – The T90 transmission was never mated to AMC engines.
Write-ups and Tutorials
To Be Completed
