Hey guys,

Somehow during the process of my engine swap I have misplaced the bolts that hold the transmission to the bellhousing (LT1 T-56). Does anyone happen to know the size of these bolts, or know if GM has a part number for replacements?

Thanks a bunch.

 

I'm pretty sure they are 3/8 coarse 1 1/4 inch long.

 

I can't remember the part number off the top of my head, but any GM parts guy can look them up. I seem to remember them being rather expensive through the local dealer - I scrounged up a mostly-complete transmission that was missing some fasteners, and walked away from the parts counter $150 lighter in the wallet I think those bellhousing bolts were around $2/each.

Shoot me a PM if you can't get ahold of the part # and I'll look it up in my filing cabinet at home.

 

Hey guys, thanks a bunch. Just wanted to let you know, GM doesn't technically show a part number for this particular bolt. However, in their computer they showed a bolt for the tailhousing to case bolt, which was a coarse 10mmx1.5 bolt, 40mm in length.. of course, GM list on that particular bolt was something outrageous, like $8 per bolt. The guy at the counter said "I can hook you up though, $4 a piece.." Yeah, thanks a lot. Heheh..

Anyway, so I went to a local fastener place and bought some grade 10.9 bolts to try, for $.69 a piece, and they were perfect. I have no idea why the GM manual lists the rear fasteners but not the trans to bellhousing. I also needed pressure plate bolts (which are a very specific thread and shoulder length for the LT1 clutch), but the GM dealer had them in stock and at a reasonable price.

Transmission is now in. One thing down, one hundred to go.. thanks again.

 

I went to a local fastener center and the guy gave me the all the bolts I needed for about 10$.

Sounds like you made out Ok, too.

 

Just be careful with hardware-store bolts - it's very rare to find one that is of the same quality as an OEM fastener. In this case, it's no big deal since the aluminum threads in the transmission will give way well before the bolt will, but it's something to keep in mind the next time you're looking for new hardware for something more critical.

 

Absolutely correct.

That is why I went to an Industrial fastener outlet, and specified that I wanted only grade 8 or better.

 

Even at that, you may not get the same quality that you get from the OEM. The SAE bolt-grading system is of little or no use of determining a fastener's quality, unfortunately. In this situation, no big deal, but if this was something like a brake-caliper bolt, it might be an issue.

Carroll Smith goes into further detail on this topic at various points in his book series.