What is needed to convert a 4wd TH400 as a 2wd drive unit? Outpushaft and tailshaft housing?
Thanks!

-Eldon

 

Up here the transmission guys actually look for 4x4 cases, they say they are stronger. And other than that like you said , depending on what it is going in the right length of tail stock and output shaft, , Ron

 

Make sure when you get a tail housing that its the one designed for the thick wall yoke. They made some thin wall yokes and tail housings that only work with retarded double cardan u joints and you cant get a stabdard yoke thats thin wall.
The best cases are indeed some 4WD ones and you can identify them by a cast aluminum converter cover and the 3/8 bolt bosses around the perimeter of the lower bellhousing. Its not that big of a deal though since i built one with the standard case and it lives in the bottom 8's on a regular basis.

 

Getting my thread jack out and I'm sorry but, what valve body are you guys running in your TH400s? Mine just has a B&M shift kit and the more I turn to boost up the slushier it gets.

 

I know the guy's around here look for the 8 bolt case so they can put the ultra bell on it.

 

TCI part # 221100 in mine worked great behind a healthy big block for years, Ron

 

Yep! If you approach 1000 hp you DO need to add a shim in the press. regulator spring to get to 220 lbs line pressure. The TCI kit falls a tad short on line pressure but otherwise is a GREAT valvebody kit.

 

Eldon,

Yes, and you can probably sell the 4wd output shaft easily for decent money.

Dave

 

trbo355,

I respectfully say, not true on the thin o.d. yokes. There are normal small od single u-joint yokes on mid 60s buicks. Those cars use a truck-like 2 piece driveshaft and carrier bearing. I have one or two of those yokes here, fwiw. Much better to use the thicker yokes and matching tail housings though, I admit.

Eldon,

I've never looked at the 4wd cases, but I would try to find an "8 bolt" case for a max effort. 8 bolts on pump flange. Not sure when GM brought the 6 bolt cases out. I've seen them with a '76 date code for sure in Cadillacs. They lightened up the cases on the 6 bolts for sure.

Btw, just because a trans has a 6 bolt pump doesn't mean you will not find an 8 bolt case there. 6 or 8 bolt pumps will work on either case. Transmission shops often used a 6 bolt pump on an 8 bolt case during re-builds.

Also, after apx 70, maybe 71, *maybe* 72, they used a roller clutch on the back of the intermediate drum. Prior, a sprag was used, and that is pretty much a must for a high horse deal. The older 400s with a sprag on the drum will save you a few bucks there.

Dave
p.s. - anyone that finds a 65-67 Buick olds or caddy th400 with 2 wire connections and short splines on the pump body, I'll buy it or parts from it. [they are "switch-pitch", and normal "race" convertors will not work in those pumps]. Splines on the s-p pumps are apx 5/8" long, vs apx 1.25" long on normal pumps. I'll also buy the convertors from them, as well as convertors from "2 wire" 64-67 buick and olds 2 speed transmissions.

 

I wasnt aware that they actually made a thin wall yoke in the standard u-joint pattern. I tried to find one years ago and came up empty handed. Thanks for the info!
On the subject of sprags, some of them even had a sprag on the low roller assy. but i have no idea what app. they were used on. It seems like the common roller clutch doesnt give much trouble so it might not be a 'must have" in a high HP application. Definitely do the intermediate sprag and buy the fancy 32 element upgrade. A new smooth drum van be bought for around 40 bucks to backdate any trans. I have seen those sprags fold over but it takes about 1500 hp to do it! LOL It didnt even break the outer ring but sure as hell it flipped the little peanut shaped sprag thingys over. The car also ran 7's and probably shouldnt even be running a TH 400 at that level

 

355,

I thought that all of the early 400s had the sprag on both, but I always ASSumed that it wasn't needed.

I have been told to beware the aftermarket drums, as well as re-machined factory drums, but I'm not experienced with either.

Dave

 

Yeah im a bit rusty on all the details but im sure i have pulled apart early ones and only found them to have the intermediate sprag and standard low roller. One day i pulled apart a BOP case that had a long tailshaft and it had the good sprag in the back. At that point i never knew they even existed! So i could possibly be wrong on some of my info.

 

I always through that if they had one, they had both. Who knows what's been changed [or swiped] by shops that have worked on any trans over the decades. No offense meant to trans shops out there, but I know that it's happened.

Dave