The Borg-Warner T98 is a heavy-duty truck style four-speed transmission. It was introduced in 1948 and used until 1964. It began to be installed in Jeeps starting in 1955. It was a special order transmission for Jeeps through 1972, making it a somewhat rare transmission to find in Jeep CJs. It was more common in military versions of the CJ such as the M38A1. This transmission was standard in the M715 and M725 military trucks.
The T98 is synchronized in it’s second through fourth gears. All gears are helically cut except first and reverse, which are spur gears.
This transmission can be found behind Ford, Jeep and some International Harvester trucks.
Jeep – When found behind the Hurricane F-Head 134 I4 engine, the transmission has a 15/16″ x 10 spline input shaft and 1-3/8″ 6 spline output shaft.
When found behind the Super Hurricane L-Head 226 I6, the transmission has a 1-1/8″ x 10 spline input shaft and 1-3/8″ 6 spline output shaft. These were in the M715/M725 military trucks only.
Ford – When this transmission is found behind a Ford engine, it typically has a 1-1/8″ x 10 spline input shaft and a 1-3/8″ 6 spline output shaft.
The Jeep factory service manual recommends changing the T98’s transmission fluid every 10,000 miles. The factory oil calls for SAE 80W or SAE 90W but those are no longer available. Instead, use a conventional style SAE 75W-90 or SAE 80W-90 gear oil. Ensure the oil is safe for brass synchros.
Gear Ratios
| Reverse | 7.82 |
| 1st Gear | 6.40 |
| 2nd Gear | 3.09 |
| 3rd Gear | 1.69 |
| 4th Gear | 1.00 |
Fluid Type and Capacity
| Lubricant | SAE 80W GL4 SAE 90W GL4 |
| Capacity | 1.75 qts (1.65L) Fill to hole |
Other Specifications
| Weight | 145lbs |
| Length | 11.87″ |
| Height | 17.5″ |
| Input Splines | 10 |
| Output Splines | 6 |
| Pilot Tip Diameter | unknown |
Transfer Case Compatibility
The T98 was mounted with the Jeep Dana Spicer Model 18 transfer case, and only small input bore versions. All 4WD T98s used a rear cast iron adapter plate about 1″ thick.
The T98 was also available attached to the Dana 20 transfer case in 1962-1965 J Series trucks.
The 1967-1969 military M715 and M725 trucks only used the T98 as their transmission. This was a 2WD transmission style that was married to the New Process 200 transfer case via a jack shaft.
Engine/Bellhousing Compatibility
GM – The T98 found in the M715 and M725 trucks are ready for GM power through the use of Novak’s adapter assembly found here.
AMC – The T98 was never joined with an AMC engine.
Write-ups and Tutorials
To Be Completed
