I have been doing alot of studdying for the last few months about these transmissions, and I recently started rebuilding them. I also did a T56 swap on my suburban. And durring this entire project the same question kept popping up and still pops up today. Can an LT1 tranny be used on an LS1 or vise versa? Well I now have the proof of why it will not work. As it stands you can not just bolt an LS1 transmission up to an LT1 or the other way around. The biggest and formost problem is the input shaft differences. The LT1 input shaft is 5 5/8 inch long, while the LS1 input shaft is 7 1/4 inch long. So some people say what if I just use an entire package fom the bell housing to the tranny? Well I now know why that will not work either. Not only do the 2 transmissions use completely different clucth/slave setups, but the bellhousings are completely different. On the LT1 it has 6 bolts to hold it to the motor, while the LS1 has 8 bolts. The LT1 has what is called a clutch cover plate that covers the opening at the bottom front of the bell housing, while the LS1 bellhousing seals to the back of the motor and has 2 extra motor bolts at the bottom. Also the top right bolt that is on the LT1 bellhousing does not exist on the LS1 bell as it has been moved to the very top. I have some pics attached that will show the major differences between the 2. I didn't get the opportunity to see if the LS1 bell would even butt up to an LT1, but I don't even think it will do that, as it seems to be a bit bigger in diameter at the bottom point.

Now I know what you are thinking, I will just change the input shaft to fit my motor. Well if you are going to do that you will also have to change the front plate of the transmission. The LS1 tranny has a provision for the internal slave that the LT1 does not, also the LS1 tranny does not have a provision for a clutch fork. So either way you try to go you are screwed. And the only reason the input shaft is longer on the LS1 if to make room for the slave. In case you don't know how either of the setups work, I attached images of those also.

The bottom line is the 2 trannsmission are identical internally, I have rebuilt both, so there is no benefit of one over the other. So unless someone just gives you one that you insist on making work for your application, forget it. Just get the one for your setup and be done with it. It will cost you less in the long run, and will be much less of a headache.

I can only fit 5 pics on this post, so the other 3 will be on the next one.

 

And if I left anything out, or you have any questions let me know.

 

But does the difference in depth of the bellhousings correspond to the difference between the input shafts? I've used a conversion flywheel before to make up the difference in flywheel mounting depth (crank to bell mounting surface) between a sbc and ls to use an old 4spd. old style bellhousings work your just missing a bolt.

 

You realize you're responding to a 15 year old thread....???

 

So yes i know this thread started life 15 yr ago... BUT when the new c8's get CRUNCHED and a few of us buy em as SALVAGE, will the new c8's lt2 bolt up to a 4l80e tranny or any other lsX compatible tranny or TH400?? AND will the new 8spd DCT TRANSAXLE from said c8 bolt up to an LSX motor??? Please and Thank you!!!

gh426

 

Very doubtful C8 anything will bolt up to a LS motor

 

I'll bring it back. I just bolted up a dropout '04 CTS-V T56 complete assembly to my '95 LT1 in my Chevelle. Everything except the missing bellhousing bolt hole fits perfect. Input shaft is perfectly seated to correct depth in the stock old fashioned pilot bushing. The flywheel is 88 Camaro, the LT1 was much too thick. The clutch, believe it or not, after 4 tries, is a 72 Buick 26 spline 10.5" pressure plate. Shim throwout to spec. Shave the LT1 starter cone a little, bolts back in the CTS bell. The internet said it was not possible. Yes, I needed to cut the floor, I had 4 degrees down angle with the trans pushed against the floor.