355ss

iTrader: (9)

I posted this in the manual trans section but I thought maybe it would be better to post here.
I have a built Lt1 T56 w/ a twin street clutch, the whole package has about 350 miles on it. I would like to switch to a Ls1 and I have read that I will need to switch the bellhousing, front plate and input shaft. I understand why this needs to be done. But I would like to keep using the clutch setup I have. The bellhousing will bolt to the ls1 block but will be missing 1 of the 6 attachment bolts (no different than a th400 swap) correct? If I bolt them together like this the input shaft will be .400" short correct? Gm makes a crankshaft spacer that is used to bolt on the 4L80E. With this and a custom pilot bushing, wouldn't this swap work (I am not sure about the ring gear to starter interface)? I have found out that the crankshaft bolt circle is different, so if I have a custom flywheel made for the correct offset and bolt circle, is there any reason this swap won't work? Or if I switch to a Ls1 input shaft (which I think is ~1" longer) no crank spacer and add and spacer to the bell housing wouldn't this work as well?

In my mind this seems do able????

bczee

iTrader: (12)

why not just get a LS1 T56.... you will be better off and I beleive the LS1/T56 are a stronger one than the LT1 T56.

Everything will just line up and fix as they should. Sell off the LT1 trans and it would cost you too much more to pickup a LS1 trans

355ss

iTrader: (9)

I know the easy route is to just get a LS1 trans, but that is not what I want to do. I would like to reuse the trans I have since I have over $4500 tied up in it and I don't want to take a loss on it. If all I need to do is buy a $30 spacer and make my own pilot bushing it seems to me it would be alot cheaper (I have access to free machining). Even if I have to spend $400 on a new flywheel it still seems cheaper then selling and rebuying.

BaD AZz Z28

iTrader: (2)

The LT1 T56 is actually the better piece than the LS1 version. Once tremec took over for borg warner, it seems like the quality dropped, albeit slightly. But it would definately be easier to get an LS1 tranny.

Your main problem here is with trying to keep the clutch setup. One is a push style and one is a pull style. Switching to an LS1 bellhousing would remove the hookup for the LT1 slave cylinder and switching front plates would remove the hookup for the LT1 clutch fork.

Im very interested in making this setup work, but I dont know that anyone has done it yet. I hate the LS1 clutch setup (too little pedal feel for me to DRIVE the car) and I already have a street twin for an LT1, but after breaking my output shaft, I put in a TH400 and havent had to finish worrying about this.

You would have to keep the LT1 bellhousing and front plate, have a custom flywheel made to accomodate the LT1 clutch with LS1 crank, and then figure out the correct spacing of transmission so that the input shaft would be in the correct location. I think it could be done with custom parts and the right time put into it, but you have to REALLY want it, because it would be so much easier to sell your stuff and buy LS1 stuff.

More importantly, why would you want to get rid of an LT1!!

355ss

iTrader: (9)

BaD AZz Z28,
You are correct, I would like to reuse my complete setup. Now if I am thinking correctly the gm crank spacer for a 6.0 and 4l80e will put the face of the crank in the same position as a sbc, this is how people are bolting up th400 to LS1's? What I have found out so far is that the spacer is .400" thick and you can only use 5 of the 6 bellhousing bolts (doesn't seem to be a problem for many people doing the swap). So the problem now is the pilot bushing and the different crank bolt circle. Mcleod will make me a new flywheel for about $400 with the correct bolt circle and .400" offset. I would then have to make a custon pilot bushing. This seems way to easy for someone else not to have already done it. I don't have a LT1 I have a sbc. I have come to the conclusion that the 23 degree heads won't do what I want so, I will either have to switch to sb2 heads or switch to a 6.0 with L92 heads.

BaD AZz Z28

iTrader: (2)

355,

I run a TH400 now that has been on both my LT1 and LS1 without a crank spacer. I have modified the tranny mounts slightly and have a few diff. driveshafts laying around to use, but I didnt have any problem that needed a spacer. The missing bolt is no problem either. I rarely put the difficult left side bolt in when I had my T56 either, they arent going anywhere as long as the rest are in place.

Why do you need a different pilot bearing? They were the same in LT1 and LS1 cars.

355ss

iTrader: (9)

Is your flex plate flat or does it have an offset to it, what type of flex plate are you using? In my truck I have a 6.0 with the thick flange on the crank this uses a flat flex plate but the later models and ls1 all have the thin flange which requires the crank spacer. The older flex plates were flat and looked like a sbc flex. But the later model flex plates have the cranks spacer attached to them. GM released the spacer so service departments could replace the older thick cranks (no longer produced) with thin flange cranks and reuse your stock flex plate. The first 2 years that the 6.0 was produced it had the thick flange which sticks out past the back of the block by roughly .700" and the rest if the ls1 cranks only stick out about .300" This is all info I have researched and I hope it is correct. I might not need and custom pilot bushing but I am not positive that I won't.

mmmchickenboy

just so we're clear, you're not swapping bell housings due to the bolt pattern differences, correct? the Gen III/IV's have an extra bolt at top, but there is no problem using a Gen I/II bellhousing, you just don't use that bolt, the other 6 align correctly.

355ss

iTrader: (9)

Correct, I would like to reuse the tranny/bellhousing as is.

Ls1Bait

Keep the LT1!!! Im biesed