This section covers stock GM transmissions, standard modifications, gear ratios and bolt patterns. The general information provided will apply to most conversions. 

TH35O: This GM automatic was commonly found stock in vehicles from 1969 to 1981.
was used in both the 4 WD pickups and 2 WD car applications. These transmissions are  identical except when is comes to the output shaft stick out length. The 4 WD transmission used an adapter to bolt this transmission to its stock transfer case. With this adapter removed, the stock output shaft protrudes from the back of the transmission case approximately 1”. On 2 WD vehicles, these transmissions used 3 different bell housings.  Lengths of these bell housings are 6”, 9” and 12”. The output shafts lengths correspond  with these tail housing lengths. This transmission is one of the most popular choices for engine and transmission conversions due to the overall length of 21-1/2”. The 1st gear ratio is 2.52:1; 2nd 1.52:1 and a 3rd gear ratio of 1:1. When converting with this transmission we recommend that you cut the two tabs as illustrated. This allows for exhaust and fire wall clearance. When using this transmission on Jeeps that have a right hand front driveshaft, the transmission should be offset 1” to the driver side for front
drive shaft clearance.

TH400: This transmission is known as the Heavy Duty version of the TH350. We manufacture a full line of adapters to utilize this transmission. The O.A.L. is 24-1/4” long. It has a 1st gear ratio of 2.48:1; 2nd 1.48:1 and a 3rd gear ratio of 1:1. This transmission is ideal for Full size vehicles because of its  strength, however, caution should be used when using this transmission on short wheeled based vehicles due to the overall length .

700R4: This is the first automatic overdrive that GM produced. Introduced in 1982, this transmission is offered in two different bell housing / case designs (60 & 90 degree bolt patterns). The internal components of these 700R4s can be interchanged if necessary. When this transmission was first introduced, it quickly developed a bad reputation for certain weaknesses. In 1987, GM resolved all of the problems that previously existed.  In the 1990s, the name of the 700R transmission changed to 4L60. These transmissions are ideal for many conversions because of the 30% overdrive. The overall length of this transmission is 23-3/8”. It has a 1st gear ratio of 3.06:1; 2nd 1.62:1 and 3rd gear ratio of 1:1. When converting using this transmission,  Jeeps 1980-86, using this transmission, must offset the drivetrain 1” to the driver side.

4L60E: This transmission is identical to the 700R/4L60 except its an electronically controlled transmission. GM manufactures this transmission in two versions. Both these transmissions use a reluctor ring connected to the GM engine computer for proper shifting points. The first version is a mirror image of the 700R, but it requires a reluctor ring. The second version is found on some of the 1997 & newer vehicles. The case and bell housing are no longer cast together (removable bell housing design). This transmission no longer had the square bolt pattern on the output side, but  was equipped with a hex bolt pattern similar to a TH400. This transmission is 21-7/8” long, and is used in both 2 WD & 4 WD vehicles. A new output shaft is required when adapting to these transmissions.

TH400: This transmission is known as the Heavy Duty version of the TH350.  The O.A.L. is 24-1/4” long. It has a 1st gear ratio of 2.48:1; 2nd 1.48:1 and a 3rd gear ratio of 1:1. This transmission is ideal for Full size vehicles because of its  strength, however, caution should be used when using this transmission on short wheeled based vehicles due to the overall length .

4L80E: This transmission is similar to the TH400 except that its electronically controlled. This transmission does not use a reluctor ring like the 4L60E. The sensor on this transmission is internally located. The tail housing bolt pattern is the same as the TH400, but indexed with a different diameter. There are several lengths of the stock transmission output shaft.  You may be required to purchase a new output shaft. Gear ratios are the same as the TH400.