Not all Borg Warners T-5's are the same. The first T-5 5 speeds were first introduced to market in 82 in all things a AMC Spirit/Concord. In 1983 T-5 were introduced to Mustangs and are currently still used in the V-6 Mustangs. The T-5 is the only American made standard transmission to span almost 20 years of production. Because of the large quantities of T-5's produced, many parts are interchangeable. There are now over 200 different T-5 transmission assembly part numbers and still counting.
There are two basic kinds of T-5's, Non World Class (NWC) and World Class (WC). In 1983 and 84 Ford used Non-World Class T-5 to improve performance and gas mileage at the same time. The NWC boxes had 2.95 first gear set with 1st, 2nd, 3rd, gears riding on a solid output shaft. The counter gears spin on straight cylindrical bearings with thrust washer in front. 3rd, 4th and 5th gears used solid bronze sycnros. 1st and 2nd gears used fiber linings bonded to steel rings. Torque rating for the NWC was 265ft/lbs.
Ford introduced the World Class T-5 in 1985 installed with 3.35 first gear set. No longer were 1st, 2nd, and 3rd gears spinning on a solid output shaft. Needle bearings were installed under each gear to reduce drag. The lower counter gears saw tapered bearings. All main shaft synros were fiber lined steel rings to improve ring surface area while 5th remains bronze. By improving the surface area, the sycnro slows the gear faster making for smoother shifts. Torque rating remained the same at 265ft/lbs.
In 1990 to 1993 the stock Ford production V-8 WC T-5 was upgraded with stronger 3.35 gear set. The nickel content was increased to produce a harder, stronger gear. 2nd and 3rd gear ratios decrease slightly. Sycnro linings on 3rd, 4th were improved by changing to carbon fiber to further improve shifting. Longer throw shifter was installed to "easier to shift". Torque rating jumped to 300ft/lbs.
When the 93 Cobra was introduced, so was the "Cobra Spec" T-5. It was the first T-5 with a front tapered output bearing and steel front bearing retainer. The Cobra boxes also received a reverse brake and sycnro assembly where there was none before. Just about everything else remained the same. Torque rating was increased to 310ft/lbs.
1994 and 95 were the last two years Ford used the T-5 behind a V-8. In the SN95 Mustangs the bell housing in both 3.8L and 5.0L was made longer to place the T-5 shifter in the correct location to the body. This in turn made the input shaft longer. The neutral safety switch was eliminated, as it was no longer needed. Everything else remained the same.
In about 1993 Ford started offering a new service unit to the motorsport crowd. The "Z" spec T-5 is sometimes referred to as "World Class T-5". Most folks, associate the term "World Class" as meaning the best. The T-5z is a 93 Cobra T-5 with 2.95 first gear set and .63 over drive. It has the best of everything. Hardened gears, short throw shifter, steel front bearing retainer, and tapered output shaft bearing. Best of all it has a torque rating of 330ft/lbs. This T-5 can handle up to 450 hp if not drag raced.
Today's V-6 Mustangs sports the last of the T-5s. The T-5 behind the 3.8L is a 3.35 first gear set with a .68 over drive. What makes these different from the rest is the electronic speedometer trigger. No longer is there a mechanical driven cable system. It has the longer input shaft equipped with a steel front bearing retainer and reverse sycnro brake assembly. Torque rating is 300ft/lbs.
Ford also used the T-5 in 2.3L through the years. While the 4 cylinder T-5 may appear to be the same they are not. Most 4 cylinder T-5s received a 3.97 gear set with a .79 overdrive and small input pilot bearing shaft. Four cylinder T-5 should not be using behind a V-8 even when the pilot bearing id is decreased to match. Simply put they will not hold up. Torque rating ~240ft/lbs. Besides first gear is much too low to be usable.
So as you can see not all T-5's were created equal. T-5's are a smooth shifting, strong, light weight transmission that can be used for daily driving or medium racing. One last piece of important information. ALL T-5 use ATF oil and NOT heavy gear oil or Redline MTL!