Im intending to do this swap in my 85 Transam 305TPI.
Our stockist here in the UK has the aftermarket T56 part#1386000011 with gear ratios of 2.97,1.94,1.35,1.00,-.84,-.62
I have a rear end ratio of 3;27
I will also need a bellhousing and again the stockist keeps a T5 one part#14075722 which it says mounts a T5(so i assume T56 also)gearbox angled to the left.Does the t56 have to be angled or vertical?Is there anothe bell housing i can buy to fit the T56 straight in?
Does this sound right to you guys?
What clutch and flywheel is best??
Would i be better off to buy a new GM box from a late model transam with the different gear ratios
thanks

PM

 

IMHO you'd be better off with a stock LT1 tranny. The ratios are better (same 1-4 but more overdrive in the '94-'97, or if you get a '93 style it has the same .62 overdrive but a deeper 1st gear which would compliment your 3.27 rear.) You can use the stock driveshaft and torque arm, but you'll need a Centerforce flywheel since you have an early-model engine. It will also line up with the console very well. By comparison, the aftermarket T-56 requires you to shorten your torque arm and driveshaft, but lets you use a stock T5 style clutch setup. But since you're converting from automatic, you have to buy a clutch and flywheel anyway.

I'll post the ratio information for GM T-56's in just a minute.

 

Let me correct myself. I replied before checking my information and had my ratios mixed up....that aftermarket tranny uses the '93 M29 ratios. The M28 tranny has a deeper 1st gear, slightly deeper 3rd, and all the rest are the same. So the aftermarket trans would go just as well with your 3.27 rear as a '93 GM T-56 would....so the only thing to consider is install really. Balance having to shorten the driveshaft/torque arm and buying a stock clutch and flywheel against buying a more expensive LT1 clutch and flywheel and keeping your stock driveshaft/torque arm. Take the one which appeals to you.


Here are the GM ratios for comparison.

trans.............1st....2nd.....3rd.....4th....5th.....6th.....R......TQ rating

'93 M28.........3.36...2.07...1.35...1.00...0.80...0.62...3.28.....350ftlb
'93 M29.........2.97...2.07...1.43...1.00...0.80...0.62...3.28.....400ftlb
'94-'97 MN6...2.66...1.78...1.30...1.00...0.74...0.50...3.28.....450ftlb
700-R4..........3.06...1.63...1.00...0.70......................???......????

 

A stock LT1 flywheel can be modified to work with a 2 piece rear main block/crank. I know this because that's what I'm currently running in my car The center hole in the flywheel needs to be enlarged and the bolt holes need to be redrilled farther out on the flywheel. The flywheel I have came with my T-56 and bellhousing, so the guy I got it from had had it machined. If you want to do the T-56 swap but don't want to spend the $300 or whatever it is for the Centerforce flywheel, but you can find a competent machine shop I would have no qualms about using a re-machined LT1 flywheel, as I've had no problems with mine yet (approx 1500-2000 miles on new engine and T-56). That's up to you of course. Personally I'd go with a stock style gearbox vs. the aftermarket unit(Mine's a '93 style piece). Yes it's more expensive for clutches and possibly for the flywheel, but EVERYTHING else is so much easier that it was worth it to me. In the end it's your decision though. Good luck and don't hesitate to ask for more help. There're a lot of guys on the boards here who've done this swap so there's a lot of knowledge here!

-Paul

 

Thanks a lot Paul,
I too am a bit unsure which to use.The aftermarket T56 is readily available in the country,new off the shelf,so i think this may be the one i'll go for.
Ive been in touch with Spohn about supplying a Xmember and shortened torge arm.
As far as machining goes i do have my own shop,so thats no problem.
I'll just decide when i have all the prices to hand and see which works out the best.
Thanks again for your help

John

 

I know this is an incredibly old thread but curious to know how the modified LT1 flywheel held up? I'm doing a similar conversion now (t56 behind a 2-piece block).

 

I never had any problems with it at all. I did end up getting a Centerforce "retrofit" flywheel though, when I built my '92 re-using the drivetrain from the '84. It was one of those things where I had everything apart, so why not "upgrade" the flywheel since I was there anyway?

I can't make any guarantees, but I never had any issues with it!!

-Paul