4spd 4x4 to auto?

[CG]

ive been looking through old posts but havent seen a definitive answer on this...can i punt my 4spd and drop in an auto? will i need diff crossmember? drive shaft need to be modified? any info would be greatly appreciated...thanks

oops forgot to say its a 71 longbox

[mrein3]

I've posted this before. I'm surprised it didn't show up in a search.

In trucks of our vintage that came with a NP205, which is just about all 4x4s from 70-72, to switch from any manual mated to a 205 to a th350 mated to a 205 it is a direct swap.

In those days GM made the length differences up with the adapter between the tranny and transfer case. I swapped a 3-speed manual/NP205 for a TH350/NP205. I used the same crossmember and the same driveshafts.

I bought a brand new adapter and drive sleeve from the parts counter at the local Chevy dealer. The adapter I got with the tranny/transfer I bought, and every used th350 adapter I've ever seen, is cracked.

The input shaft in your NP205 behind your manual tranny is a 10 spline shaft. The input you need to go behind a TH350 has 28 splines. You can't reuse your transfer case without swapping that shaft. However when you get the tranny and transfer case bolted in your current driveshafts go right back where they came from.

If I was you I'd find me a th350/NP205 ahead of time. Split them and check the adapter and drive sleeve. Then swap both in and sell your manual/205 to recoup some of your costs.

I used the same speedometer cable and the transfer case shifter comes through the same spot in the floor. Since you are going from a 4-speed to an auto you may want to consider welding up the extra hole in the tranny hump or buying a different hump from an auto or 3-speed manual truck with the high hump.

Some guys like changing gears. My daily driver has a manual transmission. However putting the auto in my 4x4 was the best money I've ever spent on the truck in the 10 years I've owned it. And it wasn't cheap to do.

[CG]

thanks mrein3...looks like i need to find a few things now...ill look in parts for sale and also see what my 4spd should sell for.