90 Suburban TH400 to 4L80?

[Brett68]

I'm considering swapping to a 4L80. I wish I could have found a 3/4 ton 91 with the OD but I didn't.

I'm planning on moving to Alaska in the next couple of years and the idea of running 2800 rpms all the way doesn't sound like fun. I'll be towing a trailer with "stuff".

What would it take for the swap? Besides alot of $$.

Thanks
Brett in Boise

 

[Greg Ducato]

The 4L80E trans is about 2/14 inches longer than the 400. The transmission to transfer case adapter will interchange and the spline count on the 4L80E output shaft is the same as the 400. You will need to move the crossmember, probably alter driveshaft lengths, linkage for transfer case. The flywheel and dust cover are the same.Cooler line tweeking will depend upon the model of 4L80E you use.You will need a 4L80E dipstick and tube. You will need some kind of stand alone computer system for the 4L80E, I like the Compushift system, it is easy to install and use and does not require a PC to load new parameters. I may have missed something but that is the majority of it.

 

[Keitha]

Look into a 16147060 PCM to replace your ECM. The PCM was used in the 1991 + trucks and Subs w/ the 4L80e to control both the fuel injection and tranny. It will also make it easier if you get a complete wiring harness.

good luck,