Atlas 32 spline input (GM)


TH400: The 32 spline Atlas was primarily designed for the GM TH400 transmission with a 32 spline output shaft. One of the biggest problems with the TH400 transmission is that it was used in numerous vehicles which required numerous output shaft lengths. We estimate there are 7 different output lengths that the TH400 has been equipped with over the years in both 2WD and 4WD applications. We cannot fit all of the stock output shaft lengths; however, the Adapter Selection Charts on Pages 9 & 10 will assist you with the adapters we do offer. If you do not find an adapter housing to fit the output shaft you have, you may be required to change out the output shaft or use one of the different spacer adapters to fit your shaft length.

4L80E: This transmission was designed by GM to replace the GM TH400 transmission. Like the TH400, the 4L80E has a 32 spline output shaft. The major difference of the 4L80E is that the transmission index diameter is different than the TH400. We have seen 5 different output shaft lengths that were used in the 4L80E transmission. The Selection Charts on Pages 9 & 10 list the adapter plates that would be used only with the 4WD 4L80E transmission. If you have a 4L80E that has a longer output shaft stick out and the length matches an adapter we have listed under the TH400 section, we can modify a TH400 adapter to work on the 4L80E transmission. The early 4L80E transmission up to 1995 is normally equipped with an internal reluctor ring on both the transmission input shaft and output shaft. The computer takes both of these readings for the proper shifting and operation of this transmission. We have always ignored the reluctor ring requirement for this transmission since it is internally regulated. We have now learned that the rear reluctor ring is not always installed into the transmission. The basic rule of thumb is 4WD transmissions up to 1996 should have a rear reluctor ring in the main transmission case. All 2WD transmissions should have the rear reluctor in the main transmission case. The 1997 & newer 4WD 4L80E transmissions have a sensor provision; however, the reluctor ring in the transmission is left out. Since this transmission is expensive to rebuild and have a reluctor installed, we now offer a reluctor ring on the adapter housing. The reluctor on the adapter for a Atlas 2 speed is (P/N 50-6409), and for the Atlas 4 speed is (P/N 50-6410). These kits will always provide a 1-to-1 reading on the output even if the transfer case is in low gear. The VSS reluctor in the tailhousing is also an option, but it would require a low range switch to be integrated into the computer system.

Note: The information on years and models of the 4L80E transmission mentioned in the above section was obtained from various sources. You should always verify what your transmission is equipped with before beginning a conversion, especially with the 4L80E transmission.

6L80 2 & 4WD: 6 speed automatic is also a 32 spline transmission. This transmission can be used with our 50-9600 kit. The VSS tailhousing option would provide the GM computer the speedometer signal for this application.

GM NV4500 4WD: The GM NV4500 4WD transmission can also be coupled to the Atlas. The stock GM adapter housing has the right index diameter for the transfer case; however, the bolt pattern is incorrect. We have found it easier to use a stock Dodge tailhousing or our replacement Dodge housing, P/N 51-0205. Either one of the 6.300" long adapters coupled with our 1-5/8" spacer adapter, Part No. 51-0220, allows you to use the stock GM 32 spline output shaft. This casting will not fit the GM harmonic balancer; a spacer tube must be used to replace the balancer on this application.

GM Inputs: Since all of these transmissions are used in larger vehicle applications, we have had requests for upgrade options on the Atlas. One limited upgrade offered for these transmissions is the heavy duty Atlas input. This was developed for some applications that had an increase in horsepower and needed extra strength. The heavy duty input is not needed for all applications, but it's available if you feel you'll need it.

32 Spline Input For: Part Number: Transmission Shaft Stick out Length:

Atlas 2 Left & Right Drop: A32 .250"

Atlas 2 H.D. Left & Right Drop: A32HD .250"

Atlas 4 Left & Right Drop: A432 .500"

Stick out length is the length that the shaft protrudes from the rear of the transmission with the adapter installed. The measurement is the length that the Atlas will accept.