# TH400 trans help



## gotyorgoat (Jun 19, 2011)

My junk needs a new trans, but the best rebuild quote that I can find is $1,100. I am thinking of buying a rebuilt TH400 off of craigslist for about $300 (there are several to choose from) and trying to bolt it up myself. 

Is any TH400 going to bolt up to my '72 455, or is there something specific that I need to look for? Is a chevy truck trans the same one found in our pontiacs? Does it need to be from the same year, etc? Long shaft or short shaft?

On a general question, how easy is it to bolt up a trans assuming I have the right jacks to raise it up?

Thanks for the help.


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## geeteeohguy (Feb 2, 2008)

You need a short tailshaft trans for Buick, Olds, and Pontiac. '67-'77 or so. Chevy is the wrong bolt pattern. Other than being really heavy, a TH400 is a simple bolt-in install. Replace the torque converter while you're at it and flush the trans cooler in the radiator. (The flush comes in a can and is available at NAPA, etc.


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## kilkm68 (May 5, 2011)

I have a TH400 out of a '69 GTO sitting under my bench at home. PM me if your interested.


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## gotyorgoat (Jun 19, 2011)

I found one down the street out of a 66 Pontiac 389. Does this look like it would fit?

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## BearGFR (Aug 25, 2008)

gotyorgoat said:


> I found one down the street out of a 66 Pontiac 389. Does this look like it would fit?


Convert it to a short tail shaft and it should drop right in. If you're car already has a TH400 you should be able to swap the necessary parts, as long as they're not broken.

One of the most common things in a TH400 that will break behind a motor that makes serious torque (like a healthy 455) is the intermediate sprag. Any good trans shop should know this, and rebuild with a heavy duty srpag as a standard part of any performance rebuild.

Bear


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## jetstang (Nov 5, 2008)

Per my tranny guy, the longshaft BOP 400 is a turbo 375 with a turbo 350 yoke, and isn't convertible to short shaft, but you can use your original driveshaft with a chop. I don't know yet what this will do to pinion angle, but he didn't act like it would be an issue. I never heard of a 375, but am sure he is right. He said Pontiac had a bunch of 350 driveshafts sitting around, so just converted the tail so they didn't have to retool their driveshafts.


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## gotyorgoat (Jun 19, 2011)

My current trans has a 10" tailshaft. It seems longer than the short shaft but maybe not as long as the one pictured above. I hate to pull it off without having the replacement ready, but might be where I am headed.

Is a 10" shaft typical?

Thanks for the help


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## gotyorgoat (Jun 19, 2011)

I bought it for $250. It had the same tailshaft and was rebuilt 1,000 miles ago, so hopefully it works out. It looks pretty clean, so I'll let you know. thanks for the input.


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