David DeCan

Hey Guys. I just picked up a TH 400 off Craig's List. My question is will it fit my 70 Cutlass that we are dropping 455 in?

Seller said it was BOP. Then said it was out of a Cadillac with a 425? BOP means Buick Olds Pontiac--right? Supposed to have been running, driving. We'll see. I am kind of looking at it as a core.

I always thought there were only two 400's----Chevy and BOP cases. Chevy bell comes to point. BOP is more inverted like a V.

It is a short tail shaft and cost $80 bucks to I grabbed it.

Can I use the torque converter
Can I use the yoke the 400 has in it?
Will my TH 350 in the car yoke fit?
What about drive line. I know 400 sits in back cross member mounting wholes on frame.
Shorten drive shaft? How much?

You will remember I got a Chevy 12 bolt I am installing. Going to do it all at once. One drive line swap.

Is there any drive line from any Cutlass combo that will work factory?

Last question: Aside from dropping the pan and see if there is a lot of material shavings gunk in it, is there any way to discern if the thing works?

Oh--best shift kit to buy for these?

Thank you!!
David

oldsmobiledave

BOPC case. Cadillac included so it will work. A plus is that it has the webbed case which is better.


The converter will work but better to use a converter of known stall matched to your cam & vehicle weight.


Transgo shift kit is best.

jensenracing77

Will work. Chevy is the only oddball.

transman74

You can use the converter, but I wouldn't. My reasoning is it's used, and the internal condition is unknown. Like your transmission ( you look at it as a core), the converter is also IMHO a core.
Drop the pan and see what may or may not be in it. The only way you can truly find out what the condition of it is like, is to take it apart.
There are 3 different Transgo kits you can put in. The SK400 small kit which is just fine for a normal driver, the 400-2 if you want a more aggressive kit, and lastly the 400-3 which will give you a manual valve body, fine for racing, but a bit rough for normal driving.

joe_padavano

And Jaguar, and Rolls Royce, and Ferrari, and Buick Nailheads...

To the OP, I'm curious what Caddy came with a short tail TH400. Early Seville, perhaps? Can you post a photo of the ID tag?

jensenracing77

lol, I did not know I sent this.... I was taking a brake at work and jumped on CO. I was interrupted and never got back to it, or so I thought.

TripDeuces

My first thought also. Guess I'll wait to see.

quaddriver

BPOC - I woulda mention Jaguar but someone beat me to it....

You can use the 350 converter and it will produce more torque (or so says my tranny guy, I still say its all voodoo and smoke) but big things like big things. You can get a reman zero issue converter for $120.

Yoke - different, and expect to slice and weld the driveshaft. The 400 is 10lbs-ish heavier and some of that is rotational mass and takes a few hp away in a stock motor, but, unless faulty, you will not kill a 400 in a street car. One of those no-brainer issues in my book...

Koda

What about AMCizzles?

TripDeuces

Always saw Chrysler products on AMC, 904 and 727

quaddriver

the 400 was an option behind 3 sixes, and all the 8's, amc, buick and the kaiser 327

Koda

Indeed. I learned to drive on a 78 CJ7 with a AMC 304, a quadrajet, a th-400, and a Ford distributor.

rocketraider

425 indicates a late-70s Cadillac on the downsized chassis, so might have had a short-tail 400. Even downsized Caddys were heavy so the guts of this 400 ought to be pretty stout, but expect it to be calibrated for "invisible" shifting. Can't be jerking society matrons around on their way to bridge club...

joe_padavano

Yup, beat me to it, Glenn. I just reread the first post that mentioned the 425 Caddy motor, which you correctly pointed out was late-70s. I wasn't thinking of the downsized 77-up "full size" cars. Good call.

transman74

Don't use the 350 converter, built for lighter duty than the 400 converter and the stall speed is the same on both converters. Stock 350/400 converters stall around 14-1600 rpm. The trans guy that says it will produce more torque has been into some funny smoke. Converters do not produce torque, engines produce torque.

BlackGold

You're right, converters do not produce torque out of thin air. But they do multiply torque, just like a gear set can multiply torque. Given an input shaft spinning faster than an output shaft, you can design a mechanism to increase torque. Which is exactly what a torque converter does. It's not just a slush box letting things slip.

Chumley

As far as shift kit, I used B&M 40 years ago, but I don't know if they still exist. Awesome performance though, just in the intermediate mode.

transman74

You're right of course, I should have made my statement clearer. A torque converter is a torque multiplier. My purpose was to point out that there is no difference between a TH350 or a TH400 converter from a stall point of view, in most cases. Yes there is the LS7/TH400 converter (rare item) that was a GM factory high stall, and if you find a smaller TH350(11") converter (Vega comes to mind) it will stall higher behind a V8. However, your typical GM 350/400 converter stalls between 1400-1600 rpm.
When I worked in the industry, if you phoned about a non-lockup Chev V8 TH350 converter, you got our part number C-9. For your typical TH400 it was a GM3, a 3 mounting pad converter. There are other 400 converters of course, but on a bad guess, 80% of the 400 converters we sold was the GM-3.

matt69olds

Drop the pan for.inspection, if its relatively clean use it. Plan on putting a shift kit of some kind in it, and replace the converter with something more suitable for a stout street car. The Cadillac converter will be way too tight for your car, the stall speed is probably less than 1600-1800 at best. The trans will have girlie-man shifts, cant have that in a hot rod!

David DeCan

Thanks for your insights everyone. New pic tonight of the ID plate off the TH 400. Perhaps someone could positively ID this unit.

Second question: I have been dying of curiosity at the condition of the unit. Was going to flip it over tonight and pull the pan. Then thought better of the idea as I really need to see what is in the pan and not pour any sludge shaving etc into the trans.

Am I thinking right? Should I remove the pan from the bottom--as if it were in a car? Any thoughts on supporting the trans while I remove the pan? I have an engine stand, should I support the trans at the bell housing connected to the engine stand and remove the pan from the bottom thereby containing any sludge in the pan for examination and not pouring it through the unit?

These trans are so tough, does anyone think there is a possibility I might not have to rebuild it? If the pan is in fairly good shape should I drop a shift kit in it and install and hope for the best?

I think the recommendation is to replace the converter regardless because it can can contain a lot of garbage. As well the stall is going to be way off for a 450-500 HP 455 with 3.30 gears.

Thanks.

David