Not All T-5's are Created Equal
Not all Borg Warner/TREMEC T-5's are the same. The first T-5 five speeds were introduced to market in 1981, in all things, a AMC Spirit/Concord. In 1983, T-5's were introduced to Fox body Mustangs and are still used in the 3.8L V-6 Mustangs. The T-5 is the only American made standard transmission to span more than 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.
World Class & Non-World Class
There are two basic kinds of T-5's, Non World Class (NWC) and World Class (WC). The first T-5 was non-world class. In 1983 and 84 Ford used the Non-World Class T-5 to improve the Mustangs performance and gas mileage. All the V8 NWC boxes had 2.95 first gear set with .68 overdrive. All the main output shaft gears and 1st, 2nd, 3rd, gears riding on a solid output shaft with deep oil grooves to provide lubrication. The lower counter gears spin on straight cylindrical bearings with a thrust washer in front to provide support when under load. All the synchronizer rings are made of solid bronze which are of different size than those found in a would-class T-5. It is because there is no bearing under each gear and the bronze synchro rings that the NWC use the heavy 70w gear oil. Torque rating for the NWC was 265ft/lbs.
1985, Ford introduced the World Class T-5 installed with 3.35 first gear set with a .68od behind the 5.OL. T-5 was also used behind both the standard 2.3L with a 3.97 first gearset and the SVO Mustang. SVO received a one year only 3.50 first gear ratio as the 3.97 gear ratio was too low for the added power of the turbo charged 2.3L. No longer were 1st, 2nd, and 3rd gears spinning on a solid output shaft as needle bearings were installed under each gear to reduce drag. The lower counter gears saw tapered bearings to replace the bronze thrust washer. All main shaft synchro's were fiber lined steel rings to improve rings friction surface while 5th remains bronze. By improving the surface friction the synchro slows the gear faster making for smoother shifts. The design remained the same until 1989. Torque rating remained the same at 265ft/lbs.
1990 to 1993 the stock Ford production V-8 WC T-5 was upgraded with stronger 3.35 gear set by increasing the nickel content to produce a harder, stronger gear. 2nd and 3rd gear ratios were decreased slightly tp provide more torque to the rear wheels. Synchro linings on 3rd, 4th were improved by changing from fiber linings to carbon fiber to further improve the friction surface resulting in better high rpm shifts. A longer throw shifter was installed to "make shifting easier". The speedo drive gear was changed from 7 tooth to 8 tooth. The 8 tooth was a step backwards when installing lower rear axle ratio greater than 3.55 as the driven gear is limited to 21tooth count. Yes, 23 tooth gears are available but do not last long as the teeth are thin and do not mesh correctly. 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 gear brake and synchro 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. With the introduction of the SN95 Mustangs, the bell housings in both 3.8L and 5.0L were made deeper 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. The GT 5.0L Mustangs received the standard input shaft bearing and aluminum bearing retainer, where the Cobras continued with the tapered or "cupped bearing" input shaft and steel front bearing retainer. Torque ratings for both remained the same as the 93 T-5 models. 4 cylinder T-5s were no longer needed when the 3.8L V6 motor came along and was replaced with 3.35 first gear ratio and a .68od. The only difference between the 3.8L and standard 5.0L T-5 was the input shaft length. Changing input shaft of the 3.8L T-5 with 93 input shaft, will result in a 93 and early spec T-5. Everything else remained the same.
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 synchro brake assembly. Torque rating is 300ft/lbs.
Ford also used the T-5 in 2.3L cars 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's should not be used 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 behind a high horse power car.
The "Z" Spec T-5
In 1993 Ford started offering a new service unit to the motorsport crowd. The "Z" spec T-5 (Ford part number 7003Z, also sometimes referred to as "World Class T-5". Most folks, associate the term "World Class" as meaning the best, however world class T-5 were introduced in 1985 as stated ealier. The T-5z is a 1993 Cobra T-5 with 2.95 first gear set and .63 over drive. It has the best of everything. Hardened gears, short throw factory shifter, steel front bearing retainer, and tapered output shaft bearing ands a seven tooth speedometer gear. Best of all it has a torque rating of 330ft/lbs based on 100,000 mile usage. The stock T-5Z can handle up to 450 hp when not drag raced.
Aftermarket Super Heavy Duty T-5's
Now that after market companies offer new and improved gearsets, T-5's can now handle up to 600hp and are used in drag racing on a regular basis. The advantage of this setup is the small platform which will spin up faster than a heavier TREMEC or Richmond transmission.
Borg Warner and TREMEC
About 1998, TREMEC bought the T5 product line from Borg Warner and have produced the T5 used ever since. Note that the transmission is the same although the case stamp will say TREMEC or Borg Warner depending on who manufactured it.
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, spirited driving, or all out racing. How you set up your T-5 is important so you get the most from it.
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One last piece of important information.
ALL World Class T-5 use ATF oil and
NOT heavy gear oil or Redline MTL! All NON-World Class T-5 use 70 wt gear oil. We recommend high quality Synthetic oil as it lasts a long time and over a larger operating temperature. It is important to change the oil in your transmission based on how you use the vehicle. If the vehicle is your daily driver then changing the oil every two to three years is fine. However, if the transmission sees regular track duty and pushed hard, then once or twice a year is in order. When we rebuild transmissions, we can tell when the oil has been changed often as the parts are much cleaner with less over all wear. There is no filter inside the manual transmission only a magnet at the bottom to pick up the metallic particles in the oil, the only metallic parts in a transmission is the gears or bearings. Oil is cheap, transmissions are not!
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Everthing You Have Ever Wanted to Know About T5's 
