Tremec 5 speed conversion questions
Thread Starter
Drifting
Joined: Jul 2020
Posts: 1,500
Likes: 323
From: San Diego
Tremec 5 speed conversion questions
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?
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?
Race Director
Joined: Jul 2018
Posts: 10,519
Likes: 8,230
From: San Antonio, TX/Mahopac, NY
2024 Corvette of the Year Finalist - Modified
2024 Corvette of the Year Finalist - Unmodified
2023 C7 of the Year Winner - Modified
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!
Burning Brakes
Joined: Nov 2004
Posts: 1,193
Likes: 176
From: Hillsborough NC
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.
Melting Slicks
Joined: Nov 2006
Posts: 3,380
Likes: 1,800
From: Apple Valley, MN
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.
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.
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,013
Likes: 4,367
From: Marlton NJ
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.
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.
Safety Car
Joined: Dec 2012
Posts: 3,974
Likes: 673
I agree
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!
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
10 Most Common Corvette Problems of the Last 20 Years!
Joe Kucinski
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
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
https://www.ebay.com/itm/11478422767...xoCcA0QAvD_BwE
Last edited by derekderek; May 5, 2021 at 07:32 AM.
Safety Car
Joined: Dec 2012
Posts: 3,974
Likes: 673
t56
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
https://www.ebay.com/itm/11478422767...xoCcA0QAvD_BwE
Racer
Joined: Mar 2021
Posts: 278
Likes: 43
From: Kansas
Old Pro Solo Guy
Joined: Dec 2017
Posts: 8,013
Likes: 4,367
From: Marlton NJ
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.
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.
Last edited by leigh1322; May 5, 2021 at 03:29 PM.
Racer
Joined: Apr 2009
Posts: 330
Likes: 44
From: Cincinnati Ohio
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.
Team Owner
Joined: Jan 2006
Posts: 39,344
Likes: 171
From: Into the Mystic And yet, despite the look on my face, you're still talking TN
St. Jude Donor '09 thru '25
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
Last road trip 75-80 mph on the freeway and I got 22 mpg