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Jun 14, 2001
1978 custom
Hi all,

Anyone have any experience with any 5-speed tranny conversions? I'd like to be able to find something out of a production vehicle. I've currently got a T10 in my '78 that needs to be replaced or at least gone through very thoroughly, right now it sounds like a M22 rockcrusher with the straight-cut gears:)

With my 3.73 rear end, an overdrive would be nice, too.:)
the borg warner m5 transmission comes in 84 5 6 Z28 T/A Iroc ect is a medium duty trans at best you will need a new bellhousing and hydralic clutch unit, a 12 3/4 flywheel and small starter, the shifter is a top laoder tail mount and you may have problems with location through the floor and console.I would opt for doing the T10 over it,s a much nicer tranny, stronger too. The overdrive is .75 in 5th the output shaft is a problem area and driveshaft lenth will also be a problem as with the crossmember.
Thanks, Phoenix. I'm assuming you mean the T-5, the T-10 was a 4 speed. I just looked at the gear ratios from the T-5 and they look pretty good - deeper first gear that the T-10 plus the O/D.

Anyone else have experience with the T-5?

If you're looking at the T-5 family, one out of an F-body probably isn't what you want. They're pretty weak for performance use.

I would suggest going here:


Fortes specializes in the Tremec, which is the Mustang :( heavy-duty version of the T-5. They have units that will bolt into GM vehicles. Don't know if they've ever done a C3, but it wouldn't hurt to talk to them. A Tremec TKO can handle about 525 lb-ft of torque, so capacity shouldn't be a problem. With traction, your half-shafts would die before that!

I'm considering this swap for my 72 if & when the time ever comes.

Oh, a Tremec TKO will probably set you back around $2k or more when all is said and done. If you compare that cost to other new OD trannys, it's competitive. Plus, you get the benefits of the internal rail shifter.

You might want to look at the GM Performance Parts
aftermarket version of the T-56 six speed too.

Good Luck.
Gearvendors O/D available now

Just ordered an electric overdrive for my M-21. They just finished the adaptor tooling for their tried an true bulletproof unit. It gives you a 22% reduction in RPM in any gear. If you are nimble of feet and hands this turns the 4-speed into an 8-speed.
Ack..:) I'd hate to ask what that electronic overdrive cost..:) Sounds like a slick set up, though - anywhere on the web where I could learn more?
The unit is $2395. The website is www.gearvendors.com.
The price includes everything including the trans yoke but you will have to shorten the drive shaft. Good time to go carbon fiber or aluminum. It also has the advantage of shifting some weight to the rear. No clutch is required to engage.
Imagine wailing to 6000 and hitting the od in third then punching forth. Talk about close ratio.
Not For A C1

I agree with Phoenix, I researched a five speed for my 62 and it's not going to happen. The biggest problem I saw aside from all the underneath modifications was the top loader which would have put my shifter behind me. I rebuilt my T10 and live with the way it is with a 4:11 posi. A 5 speed would be nice but not worth the time and money to make the switch in my opinion.

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