The Stovebolt Site Forums The Shop Area Engine Shop questions on standard trans conversion

OK, here's what I've been tossing around:

I have a sbc 350/350 combo in my '58 GMC 100. The engine is tired and will be replaced soon. In my my '58 Chevy 3200 I've got an original 235 with a 3-speed trans.

I've been thinking it might be fun to put the 3-speed from the Chevy in the GMC and run it behind a mild small block. The questions are:

1. What would I need to do that conversion?

2. Does the GMC front crossmember have the same mounting holes as the chevy?

3. I have a V8 truck bellhousing that should be the correct one. What about the flywheel? Starter?

4. What size clutch did the original V8's use?

5. Do late model GM replacement crate motors have the holes and bosses to accommodate the early V8 front type mounts that I would have to have to use the early trans or would I have to run an earlier small block (283 or 327)?

6. Are there any differences in the rear crossmember between a V8 and I6?

7. What other issues can I expect to come up?

I know that's a lot of questions. Any insight would be appreciated. If it's going to be too much of a problem I will probably just keep the auto trans and replace my current small block.

Thanks in advance for any help.

I think that the frames are the same. You eill need the V-8 front mounts and the correct bell housing, the GMC had a different bellhousing because they used a Pontiac V-8 from '55-'59, they have different bolt patterns.I think the clutch was an 11". As far as I know, the GM crate engines still have the front mounting holes om all the engines-small block and big block. My GM Power Catalog is a few years old, however, that may not be so now. You have a small block in it now, so there should'nt really be any suprizes in the swap.

Thanks for the info. The samll block I have in it now uses the side motor mounts, so if I go with the standard trans/bellhousing mount, I'll have to go back to original type front mount, I imagine.

I realize that the original GMC bellhousing was different. I guess one of my questions is, are the crossmember and bellhousing mounts the same as chevy?

I'm assuming you have the original 3 spd in the 58. That tranny will not take any abuse from the SBC. There was a 64 Impala with 300 hp 327 and that 3 spd. The owner a local cop was buddies with the gas station owner at which I worked 64 to 65. I got it down to about an 1 1/2 hours to pull tranny replace slider gear and re-install. My 2 cents.

Larry

you do not have to use the front mount in order to use the standard trans, the side mounts work fine - either will work with the 3spd, but you already have the side mounts, so easier

as for abuse, unless you like to snap the clutch at full throttle, the original 3spd will hold up fine, but a later [68+] 3spd will have a syncro first [and a different spline count on the output, takes finer toothed yoke]

Bill

I found when I switched over to a standard , I started to boot it more often.At that point the stock trannies started to snap like tooth picks.After 8 of them I went to an M21,it lasted a month ,so I tried a M22, same story, 1 month.I found a full syncro 3 speed from a 69 Firebird.No matter what else I blew, that tranny lasted till I sold the 56 Nomad 3 years later.The new owner threw out the tranny because he liked automatics better.That was back in 1980. I haven't blown a tranny in over 20 years now,I guess I'm smarter now,haha.Just don't drive a standard any more, that's all.

Thanks for your responses. If I do this it will be behind a mild small block, either a stocker 283 or 350. I don't plan to abuse it or go racing or anything..