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Old 06-16-2007, 10:05 AM
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Firebird th350 gone wrong

Hello all, here's my issue:
1968 Firebird w/350, had a 2 speed power glide, trying to up grade to th 350,
bought a used th 350, casting letter on top of trans is a large capital "D" (not sure what that means if anything) rebuilt trans, added shift kit new torque converter all went well till I tried to bolt up to my Pontiac 350 engine code YJ,
trans doesn't fit, only the bottom outside bolts and the alignment pins align. Flex plate and converter align! But that's it, Where did I go wrong?? I don't believe 2 bolts will hold this together! Is there a difference between Pontiac and Chevy bolt pattern?
thanks in advance
Shawn
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Old 06-16-2007, 10:20 AM
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Quote:
Is there a difference between Pontiac and Chevy bolt pattern?
Yes, one is called BOP pattern & then there's Chevy
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Old 06-16-2007, 01:29 PM
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Re: Th350 Gone wrong

The bolt pattern from the Pontiac and the Chevy TH350's are different and they are not interchangable.
The top of the bell housing on the TH350 for a Chevy is peaked.
The top of the bell housing on the TH350 for a pontiac/olds/buick and cadalliac are dipped between the two top bolt holes and only two bottom bolts line up between the two makes. They are NOT sufficient to hold.
There are "universal" bell housings but they're rare.
I KNOW thats good info for future use.
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Old 06-16-2007, 02:50 PM
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I used a JW Ultra Bell to bolt a Chevy transmission to my engine. They're SFI approved and not to hard to install. By the way, the two speed, that came in your bird, is not a powerglide. It's a Super Turbine 300. Not near a good as a glide.
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Old 06-17-2007, 06:24 AM
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The TH300 is a very good 2 speed unit, and is much stronger than a stock powerglide. For a 2 speed they were a very good unit for durability. There was a trans brake for them a few years ago. As to what their worth.......
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Old 06-17-2007, 12:45 PM
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Quote:
Originally Posted by slr1968
Hello all, here's my issue:
1968 Firebird w/350, had a 2 speed power glide, trying to up grade to th 350,
bought a used th 350, casting letter on top of trans is a large capital "D" (not sure what that means if anything) rebuilt trans, added shift kit new torque converter all went well till I tried to bolt up to my Pontiac 350 engine code YJ,
trans doesn't fit, only the bottom outside bolts and the alignment pins align. Flex plate and converter align! But that's it, Where did I go wrong?? I don't believe 2 bolts will hold this together! Is there a difference between Pontiac and Chevy bolt pattern?
thanks in advance
Shawn

As pointed out ... you need a BOP style bell housing for your engine.

BOP = Buick , Olds , Pontiac.....they fit many Cadillac engines too.

The guts of the chevy t-350 you will fit into the BOP case... There are some minor differences , but a simple thing to swap parts out for a fellow with some tranny knowledge.


post back if more questions come up

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