LS1 spec T56 behind a SBC

[bluex]

I see alot threads on this using an expensive sfi bellhousing, stock bellhousing with adapters or LT1 spec clutches etc and I'm curious as to why. I can't be the first to look into this an I don't understand why there's no information out on this.

Everything I see says to use an LS1 spec trans you need a 1/2" spacer to use a stock pressure plate and clutch. I ran into this same issue with my 97 NV3500 swap that uses the same internal slave cylinder as an F-body LS1 T56. To remedy the issue I used a flywheel for my 78 350 and a clutch/pressure plate for a 97 C1500 with a 5.7. The difference in the pressure plate finger heights between the two clutches was..... 1/2".

Since the internal slaves an throwout bearings are the same between the two then in my mind I should be able to swap to a 26 spline clutch disc an a LS1 trans should work directly with no other mods. Is there anything different between an SBC an a LS1 in where the bellhousings an crankshaft face are located?

99+ trucks with a 4.8 used the NV3500 up to 05 or so. Those guys swap to a small pilot bushing, a 26 spline disc an that's about all they have to do clutch/hydraulic wise. The NV3500 was basically the same (input shaft and slave) from 96 through end of its run.

I stumbled across a T56 for $100 a few weeks ago an I currently have a stock 2 piece rms block but will be upgrading to a 1 piece rms 383 eventually. I'd like to get the trans in and sorted before the 383 but I don't want to buy a bunch of expensive stuff twice. The trans didn't come with a bellhousing but I'd really like to be able to buy a 250 stock one not a 1k McLeod that is way overkill for my build/use.

[scottofksu]

So, I cannot be of very much help with your specific questions as I have an LT1 T56 that will get hooked to my 383 (I also used a 2 piece RMS block), but, before others with more experience get in here to provide more support, I can share what little I have learned that might be applicable.

As I understand it, the issue is in the input shaft length with the LT T56 having a 1 inch shorter input shaft (5.5" from the trans face) than the LS T56 (6.5" from the trans face) and 1.5" shorter than aftermarket T56's (7" from the trans face). The LT1, given the shorter shaft, also requires a "pull type" clutch, which is partially why I got to enjoy paying $700 for a special flywheel... Additionally in the category of "flywheel hell", I also found out in building my 383 that even the high dollar flywheel I purchased was set up for external balancing as 400's came from the factory externally balanced. This resulted in some added complexity and costs - according to my machine shop as they were pushing these extra costs to me - when I had my 383 internally balanced.

I hope some of this helps at least somewhat! LOL
In the case that it does not, hopefully moving this post to the top of the heap gets you some feedback! Good luck! Please come back with the final results if you go this route as I would love to compare notes on how you are liking YOUR 383 T56 combo!

[Joyridin]

When I bolted a transmission from a 2005 GTO to my SBC, I bought an adapter and a special pilot bushing to make up the difference. I think it was $200 for both.

The adapter bolted between the trans and bellhousing to allow the trans to bolt to the original bellhousing, and the pilot replaced the original pilot bushing. Everything bolted up and I never had a problem.

[bluex]

Originally Posted by Joyridin

When I bolted a transmission from a 2005 GTO to my SBC, I bought an adapter and a special pilot bushing to make up the difference. I think it was $200 for both.

The adapter bolted between the trans and bellhousing to allow the trans to bolt to the original bellhousing, and the pilot replaced the original pilot bushing. Everything bolted up and I never had a problem.

Ya I've seen that a bunch. The issue I have is the NV3500 has an integrated bellhousing and a internal slave already same as a LS1 T56. I don't have any stock 4 spd type clutch/bellhousing parts to use an go that route. I'd like to keep the hydraulic clutch I already have setup, since it's the same internal slave, I won't have to modify the pedal again, an I can keep the same lines, master etc...

[bluex]

Originally Posted by scottofksu

So, I cannot be of very much help with your specific questions as I have an LT1 T56 that will get hooked to my 383 (I also used a 2 piece RMS block), but, before others with more experience get in here to provide more support, I can share what little I have learned that might be applicable.

As I understand it, the issue is in the input shaft length with the LT T56 having a 1 inch shorter input shaft (5.5" from the trans face) than the LS T56 (6.5" from the trans face) and 1.5" shorter than aftermarket T56's (7" from the trans face). The LT1, given the shorter shaft, also requires a "pull type" clutch, which is partially why I got to enjoy paying $700 for a special flywheel... Additionally in the category of "flywheel hell", I also found out in building my 383 that even the high dollar flywheel I purchased was set up for external balancing as 400's came from the factory externally balanced. This resulted in some added complexity and costs - according to my machine shop as they were pushing these extra costs to me - when I had my 383 internally balanced.

I hope some of this helps at least somewhat! LOL
In the case that it does not, hopefully moving this post to the top of the heap gets you some feedback! Good luck! Please come back with the final results if you go this route as I would love to compare notes on how you are liking YOUR 383 T56 combo!

The 383 is a long time out probably lol.

My trans is a LT1 version as well but I'm going to swap it to LS1 spec. I'm not swapping over to that expensive style clutch. Plus I have none of the linkage or the bellhousing an all that ads up quickly too. I'll be much better off doing the swap to the LS1 input, even if my idea doesn't work an I still need some kind of spacer or something. I think for now I'll get the bellhousing an input shaft an try an mock it up so see what kind of spacing I wind up with on the throwout bearing.