Th 400

[ratfreak8871]

I Have A Th 400 And The Yoke Is Bolted To Output Shaft. Can I Unbolt It And Use It As A Slidding Type Yoke?

[bigblock79]

i don't thank so. but i could be wrong

[jeffspower]

I have seen it done before, but don't reccomend it. The output shaft won't allow the yoke to travel inwards very far. If it bottoms out, internal damage can happen. If you shorten the driveshaft to compensate, it can wobble on the splines, damage them, or at least wear out the seal fast. On a driveshaft with a carrier bearing, you might get by.

[magnethead]

Originally Posted by ratfreak8871

I Have A Th 400 And The Yoke Is Bolted To Output Shaft. Can I Unbolt It And Use It As A Slidding Type Yoke?

check your flywheel- if it's a big truck and the convertor and flywheel have 6 connection bolts, it's a TH475 for reference (learned that 4 days ago). TH400 with fixed yoke, bigger allison style convertor, and straight cut gears.

[ratfreak8871]

Only 3 Converter Bolts, But Yeah I Read The Thread About The Th475 The Other Day, I Didn't Even Know There Was Such A Thing. I Cant See Any Diff. Between A Bolt On And A Regular Slide Yoke Other Than The Bolt Hole, I Just Wonder Why I Cant Unbolt It And Use It As A Slide, Its Just As Long As A Slip Yoke. I'm Wanting To Change From 2pc. Shaft To 1 Pc. I'm Surprised They Would Put A 2pc. In A Short Bed Truck

[jeffspower]

1- you can't use that yoke as a slip yoke, without the bolt, it will leak fluid thru the bolt hole. At least IMO, you can't do it.

2- the bolt on yoke isn't as long as a slip yoke (at least on the dozens of them I have had apart)

3- the output shafts are different, with a bolt- on yoke, there is a machined "step" IIRC that the yoke seats against.

4- I have never seen a 73-87 shortbox with a carrier bearing. Could your truck have been a longbox originally? What year, & what engine did it come with as OE?

[ratfreak8871]

hi, Jeff, its a 79 and came with a 350. i went searching for an options sheet and couldn't find one but i did find a sticker in the glove box that says truck camper loading info and it gives the dimensions of 74" x 29". i too have never seen a short bed with a carrier bearing, also the rear spring hangers are riveted in and i can't find any evidence that it might have started out being a long bed. sounds like i'm stuck with a 2 pc. driveshaft unless i get a different tranny. think it will handle 500HP?

[grinch4om]

get ahold of a local tranny shop and change the output shaft and tail housing

[jeffspower]

Originally Posted by grinch4om

get ahold of a local tranny shop and change the output shaft and tail housing

Yep, that would be the best thing to do. But it requires a complete teardown- the output shaft is the first part that goes in on assembly. All the rotating parts go in from the front of the case. It's not all that big of job, but unless you can do it yourself or have a buddy that won't charge you much, a tranny shop will want a fair amount to do it.

That is weird that it seems to be OE with a 2 pc. Their is one other way to put a one piece shaft in it if that's your goal- have a new shaft built with a slip yoke & stub on it. You can just bolt it to your fixed yoke. Probably $250+ to do it though. But it might be cheaper than an output shaft swap & drivehaft work to use an internal slip yoke.

BUT, lets think about your 500hp question. If you are going to build a 500hp motor for it, and use it, the tranny really needs some upgrades anyway. TH400's in Chevys usually have roller clutches instead of HD sprags, & clutch packs with less plates in them. They won't handle alot of abuse. I had one of them with the weak goodies in it in a Buick Apollo years ago with a mild 455. It would blow roller clutches way too often. The last time it did it, it was on a 6300 rpm 2-3 shift. It cut loose allowing the engine to free rev like it was in neutral. Threw a rod and made that engine a pile of scrap iron

Mid to late sixties Olds & Buick TH400's usually have the HD goodies in them you want. Cheap compared to buying the stuff new. And grandmothers don't abuse trannys- so the internals can be like new. My '72 has a '65 Olds trans with the 4x4 output shaft put in it. I used the Olds case on mine, since it fits my 500 Cad. It even has the Switch Pitch (toggle switch stall converter)