th400 replacement

[75??? franken-trunk]

i was wondering on a tranny swap, th400 to th400. the one in my friends 91 1 ton duelly went out on him... the truck has a tbi 454 in it... we found a th400 out of a car like a olds delta 88 or something along those line line (big car) it may have had a small block not sure though... would that one fit are they the same length and whats not there are both 2x4 vehicals any info???

[Fordeatinz71]

noooooo...there were two different bellhousings on these...one was a B-O-P-C bellhousing (Buick, Olds, Pontiac and Cadillac) and would ONLY fit Buick, Olds, Pontiac and Cadillac motors and the other was for Chevrolet/GMC (which used Chevy engines).  you have to know what MOTOR that tranny came from...if it's anything besides a Chevrolet you CAN'T use it...

[werewolfx13]

A bellhousing adaptor plate would remedy that problem. They CAN be used, but its a bit more work.

[Fordeatinz71]

yea, i guess you could use an adapter...but just bolting it straight up won't happen.  as far as length...i think it would be the same...not positive though...

[2500HD-454]

I've done a swap like this. All you need is a bellhousing adapter. BUT you need to measure the length of both trannys from bellhousing to the end of the output shaft. Several of the passenger car trannys had short shaft trannys. You probably have a long. The difference is the tailshaft length. MEASURE. Everything else should work fine.

[werewolfx13]

I'm not sure about a delta 88, but my dad's '78 cadillac coupe deville has a th400 with a long tail shaft. Just wish the 425 wasn't such an expensive engine to build for power AND still maintain the AC compressor.

[xtremjeepn]

Go to NAPA and buy a rebuild kit. They are pretty cheap.  Probably just needs new clutches anyway.  Rebuilding a TH400 is pretty simple if you have ANY mechanical skills.