Th400 differences
 

I am needing to rebuild a th400 for a 1971 GTO project. I have a few cores to choose from but am not sure if one would have any advantages over the other. The car will be a street car with a mild 400.

The cores that I have narrowed down to are:

OG code from a 1970 442 Olds 455.

PX code from a 1976 Grand Prix 400.

PR code from a 1973 Grand Prix 455.

PR code from a 1976 Grand Prix 455.

Would either of these cores be better than the other?

Thanks

Found this thread:
https://forums.maxperformanceinc.com...d.php?t=415558

The 70 should have the right drum to accept the good sprag .... I'd use that one.


That's a nice collection of cores you have

Exactly!

IF that 70 Olds shortail had been coded OW, then i wouldnt.
Would instead go through it & offer it up for sale to the discriminating '70 W30 restorer.

When i built my first TH400 i had 3 or so cores .. i had them all apart and cherry picked every component ... case, planetaries, drums and so on i looked at every wear point ... you would be surprised at whats worn in one trans is fine in another from lack of maintenance, overheating, and any other abuses

worked out great

The case in my car is from an early 80's Cadillac IIRC. I was shaking my head when I looked it up years ago.

Thanks for the replies. I will start with the OG transmission and hopefully it will rebuild nicely. Thanks for the input everyone.

The '70 will not only have the right drum to use the 34 element sprag, but it'll ALSO have the good center support that accepts the .040" spacer ring that protects the case.

dang ...guess i need to pull the 2 th400 cores out i got the other day an take a look for the date codes, where exactly are they.


maybe ill get lucky n have a good one.

was tgere anything special about the 74 trans 45t th400 cores?

As mentioned I think the Cadallic th400 core is the beefed up one. It's been couple years since I researched cores. I remember the cores that had the metal vent tube were better that the plastic ones. 34 element sprag. Direct drum out of the 4L80E transmission. You can also pickup a heavy duty snap ring for center support, and a case saver. Cheap insurance.

100% of the Olds internals are superior to any of the other posted cores.
Except the actual tail shaft for PMD will be best.

Pick the case you prefer for originality. I would use a Big Car case for the reinforcements.