Adapting the 4L80E

There are 3 different output shafts for 4L80E transmissions, all 32 spline:

 

Output sticks out ~2-7/8” from the end of the transmission case: This is the only 4WD output shaft and basically works like a TH400 with the ~2-1/2” shaft
 

How to use with 203/205 doubler: Use stock 4WD adapter.  Drill/tap six bolt transfer case pattern into face of NP203, plug up stock holes and make a tab to hold down the idler shaft.

How to use with Magnum underdrive system: Use stock 4WD adapter, the Magnum box bolts directly to either of those.

How to use with NP205 alone: Use long 32 spline input gear in NP205 in conjunction with the TH400/NP205 adapter that matches the NP205 bolt pattern, index diameter needs to be turned down to 4.8”. Or use one of our 4l80e/NP205 adapters.

Output sticks out ~6-1/4” from the end of the transmission case: This is the 2WD shaft used in GM’s light duty trucks, this output shaft is not useful for 4WD applications and the output shaft must be changed.

Output sticks out ~7-5/8” from the end of the transmission case:  This shaft is often referred to as the RV shaft, though we’re not sure if that application is accurate.  It is splined the entire way and can be cut down to any of the TH400 output shaft lengths.  By turning the index diameter down to 4.8”, 1984 and older (85+ will interfier with transmission pan) TH400 adapters will work on a 4L80E, see TH400 options for adaptability.