th350 to th400 swap in 4x4

[67ZL1]

I have a '72 K20 with a t350/205 set up. I am in the process of doing a ground up and am contemplating on putting in a th400 due to the high hp and tq. My question is what kind of t-case shifter issues am I going to have? The info for the th400 that I can find says that it's a couple of inches longer, which I think it may move the shifter too far back.

[kwmech]

If you are going to do a complete removal--move the engine assy. forward. You will have to redo the drivelines anyways.


now that i think about it, if you measure right, you may only have to do the rear shaft

[67ZL1]

Yeah that's what I was thinking, I've got the truck strippe.d down to the frame right now and want to get my modifications done to the frame before painting. Just wanted a little reassurance from the guys that have done this, thanx.

[john@thepier]

I have done this conversion with a adapter plate from Advanced Adapters to mate the 400 to the 350s transfer case a company that specializes in parts for conversions. I used my stock high hump doghouse and only barely touched the stock opening in the shifter opening. No need to move your engine forward. John

[67ZL1]

Originally Posted by john@thepier

I have done this conversion with a adapter plate from Advanced Adapters to mate the 400 to the 350s transfer case a company that specializes in parts for conversions. I used my stock high hump doghouse and only barely touched the stock opening in the shifter opening. No need to move your engine forward. John

So other than drive shafts the only thing I have to mess with is the t-case mounts? How did this setup work for you.
Glenn

[1-tonmudder]

You will have to get another 205.The Th350 is 27 spline and the 400 is 32 spline and they both have different patterns on the end(350=4 bolts 400= 6 bolts).If it possible to pull out the 27 spline input and bore the case to accept the bigger input and bearing for the 400.

[john@thepier]

Yep 1tonmudder is right there is a tail shaft swap in the tranny as well. You use a 2wd tail shaft from a350 and cut it down for the 400 4x4 tranny. Give Advanced a call for some tech advice its free 1-800-350-2223 My set up works well and I have been using it for years. I'm currently doing a frame up so I have it out I'll snap some pictures of it this week so you can see what I'm talking about. Other wise look for a 400-205 set up there out there. The 350-205 is more than enough, just have your 350 built with good parts and be done with it. John

[67ZL1]

Well maybe I should keep my 350/205 set up. I've heard lots of negative things about the 350. Guys around here are telling me to run a 400. The engine that I built is a 406 sbc, comp roller cam with Afr heads. I have no intention to do any major 4x4'n, just want something that can take a moderate beating.

[kwmech]

A turbo 350 can be built pretty strong and reasonable. Extra clutches, HD sprag, shift kit etc.