Exploring The TF999
The TorqueFlite 999 is a Chrysler three-speed automatic transmission with an aluminum case and 23-spline output shaft. Various versions of this transmission have been around since the TorqueFlite's introduction in 1956. It is most commonly referred to as a TF999 or 999, but it is also known as a TorqueFlite 6 (very early models), TF904, 32RH, and 30RH. An early nonlockup version of this transmission was used in Jeep CJs, YJs (until '92), and some XJs, and later-model electronic shift units were used in late-model YJs and TJs until 2002.
All models of the TF999 use a planetary geartrain and a torque-converter clutch that engages in Third gear through a clutch solenoid on the valvebody. In late-model electronic-shift versions of this transmission, torque-converter engagement occurs when it receives sensor input from the PCM. Engagement is determined by coolant temperature, vehicle speed, and throttle position. Otherwise, overall operation, including shift timing and control, and early-model torque-converter engagement, is hydraulic.
There are differences between the 30RH and the 32RH transmissions used behind Jeep TJ 2.5L I-4 and 4.0L I-6 engines, respectively. The 32RH is said to have greater holding power in keeping the planetary gear stationary in low/reverse gears due to a double-wrap rear band, as opposed to the single-wrap rear band in the 30RH. The 30RH also uses fewer clutch packs and a smaller planetary. This is obviously due to the increased torque capacity of the 4.0L engine. The torque converters in these units are cooled by an integral fluid cooler in the radiator.
The TF999 has a somewhat respectable First gear ratio of 2.74:1, which, when mated to a decently low transfer gear, is ample for trail use. Overall, the TF999 has more than sufficient strength for use behind the 4.0L I-6 in our Project TJ, and can even stand up to V-8 applications (as it did from the factory in CJs behind AMC small-blocks). It is rated as a medium-duty transmission, but this has proven to be somewhat of a conservative rating for many users - the 999 has even made its way into rock buggies running high-torque V-6 and V-8 engines.
When it comes to upgrading the TF999, you can easily add a few heavier-duty components in addition to stock replacement parts during a rebuild. With just over 50,000 miles on the TF999 (32RH) in our '01 Project Jeep TJ, we were beginning to hear some torque-converter whine and experience sloppy shifts. We'd changed the fluid only twice in that time and had let it run low on a few occasions, which will certainly create the effects we were experiencing.
Seeking increased performance for the TF999, we looked to High Impact Transmission & Gear in Camino, California. High Impact offers its "Bad Boy" version of the TF999 that includes a variety of upgraded components. Parts replaced during a rebuild typically include clutches and clutch rings, front and rear bands, governer support, and seals and O-rings. A performance shift kit and a heavy-duty torque converter are also often applied during Bad Boy rebuilds performed by High Impact. To get a closer look at the TF999, we had High Impact tackle a rebuild on the unit in our TJ. Check out the photos and captions to get an inside look and find out more about these capable transmissions.
TF999 Gear Ratios
First gear: 2.74
Second gear: 1.54
Third gear: 1.00