Jd21476

I just pulled my engine and tranny from my '68. The car had a 350 in it with a 4 speed that worked fine but Id like to go with a Tremec 5 speed before I put it back in. I also plan on upgraded the power on the engine.

Questions:
1. When I separated the engine and trans the trans had a 10 spline input shaft but everything Im seeing for sale shows a 26 spline shaft
2. Who makes a good conversion kit for a good price
3. What's the difference between the TKO, TKX, TKO 500 and TKO 600?

Factoid

Silver Sport hands down. There are others, but they have everything you need and their customer service is first rate. Both my ‘64 and ‘69 Corvettes have 5 speeds from SST. The number 500 or 600 is roughly the torque capacity of the tranny. The TKX is a relatively new offering from Tremec with a better fit profile. I would call SST and they will answer all your questions. Good luck, you will love it!

navet72

I agree with Factoid, Silver Sport is definitely the way to go. Have one in my 70 now. Great customer support and really is a bolt in job. All the little parts were included.

73sbvert

When I get ready to put in a TKX in my '73, I'm calling SST!

SLVRSHRK

I used American Powertrain when I did my conversion. Kit was complete and everything worked. Would recommend making sure you go the C3 kit route rather than just buying a tranny and piecing it together yourself. To me it was worth it to have the shifter work, mounts and driveshaft work done and not have to think about it.

69L88

The Tremecs are one of the most popular conversions on our C3s but there are many factors to consider when you head down this path.

What are you thinking about when you state “upgrade the power on the engine”? One of the most important things to know is that the powertrain on these cars is generally able to support somewhere in the 400-450 hp/400-450 lb-ft torque range. Get over 500 and things start to break unless you breakout the wallet and start changing more hardware.

Will you plan to use the car as a cruiser only or any thoughts of racing?

What rear end ratio are you running? Any plans to change to a “deeper” gear set? The deeper the gearing, the more stress put on the driveline south of the R&P.

Which overdrive ratio are you considering? The 5th gear is an overdrive, either a .64 or .82. Be sure you understand all the factors that go into choosing this to avoid disappointment.

What tire diameter do you have now/plan to have later? See above.

There are many posts on this an other forums on the topic. Read, study, take your time and be fully informed before taking the plunge. It’s a lot of money to spend so be sure you know everything you can.

leigh1322

Ditto.
And the Tremec needs a special offset to the left shifter for a C3 only. So TKOs for other cars will not fit.
It does require permanent machining to the TKO So it is best left up to the trans mfgrs. SST makes a terrific C3 shifter. Better than others I have seen..
My TKX is on order.

509 rat

Silver sport for sure if you got the bucks do the t56 6 speed it fits no problem in my 69 .

derekderek

ok, is this the T56 everybody wants? is a boneyard one like this the same as what Silver Sport et al sells or are there significant differences? i have a T5 now and am most likely gonna use it. but...
https://www.ebay.com/itm/11478422767...xoCcA0QAvD_BwE

509 rat

The t56 is what all the top dogs are using in pro touring cars and high end builds do your home work and research your options I would have put a t56 in my 66 in a heart beat if I did not have to cut tunnel what ever choice you make both are great transmission's ,the t56 is rated for 700 ft lbs .

derekderek

it would be nice if AP or SS made a kit that was all the mounts, brackets, clutch cyls, etc to mount a specific boneyard trans...

djquik1

They are in the business to sell new transmissions and that is what they do well.

leigh1322

Maybe...maybe not.
I know some of the OEM T56 6 speeds use an insanely low OD. You get like 1200 rpm at 70.
Good for a fuel injected motor (maybe) but not for an old school carbed engine.
2000 rpm at 70 would be better.
Figure out the gear ratios and plug them in here:

Check the third tab. The 0.50 OD version is just too deep.

RU7376vettes

I went with American Powertrain and am very happy with the whole package and there were no surprises. I now have TKO600s in both my 73 Corvette and 55 Chevrolet. Love them. Shifter came up exactly where it needed to be. Pay attention to getting bell housing alignment checked.

Capt. Shark

One more vote for Silver Sport. Give Shane a call and he will answer all your questions. See my attaboy thread just a while back.

Last road trip 75-80 mph on the freeway and I got 22 mpg