5 speed
Melting Slicks
Joined: Apr 2021
Posts: 2,630
Likes: 2,088
From: Minnesota
Silver Sport has a great kit for a TKX (here). With a 3.70 rear end and a big block I would go with the close ratio 2.87 first gear. If you want a closer spread between gears go with the .81 overdrive, but if you do a lot of freeway driving I’d do the .68.
Last edited by Piersonpie; Apr 2, 2026 at 12:57 PM.
Melting Slicks
Joined: Dec 2009
Posts: 3,220
Likes: 651
From: Thunder Bay
Plenty on information on this forum. Just do a search and spend some time reading. This topic has been discussed at great length.
I have had a TKO-600 behind the 427 small block in my '79 for about ten years. The TKO has been replaced by the TKX which is supposed to be an improvement in some way.
The transmission is great. Shifts like butter after about 1000 miles of break in, although there are reports that they don't like to shift over about 6000 rpm. I don't do that so it has never been an issue.
I did my swap from scratch. That is, I collected all the parts instead of using a kit, thinking I would save some money. I think I might have saved $200. If I had it to do over again, I would buy the kit.
I have had a TKO-600 behind the 427 small block in my '79 for about ten years. The TKO has been replaced by the TKX which is supposed to be an improvement in some way.
The transmission is great. Shifts like butter after about 1000 miles of break in, although there are reports that they don't like to shift over about 6000 rpm. I don't do that so it has never been an issue.
I did my swap from scratch. That is, I collected all the parts instead of using a kit, thinking I would save some money. I think I might have saved $200. If I had it to do over again, I would buy the kit.
Melting Slicks
Joined: Nov 2006
Posts: 3,380
Likes: 1,800
From: Apple Valley, MN
Either a TKO or TKX is an excellent choice. If you don’t plan on racing, I’d recommend you look for a good used TKO and save yourself some money. If cost is no object, then go with the TKX.
Heel & Toe
Joined: May 2024
Posts: 20
Likes: 17
2025 C3 of the Year Finalist - Modified
Last edited by Ralphthehoer; Apr 3, 2026 at 01:46 PM.
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Melting Slicks
Joined: Apr 2021
Posts: 2,630
Likes: 2,088
From: Minnesota
Just look up “C3 Corvette forum TKX” on the google machine. You should be able to filter it to only show results from this website.
Melting Slicks
Joined: May 2021
Posts: 2,261
Likes: 1,304
From: Fleming Island, FL
I swap over from a 700r4 to Tremec TKX in my 82 (2.87 first, .68 OD) and I love it! I got the complete kit from Silver Sport Transmissions. I would highly recommend getting the complete kit from them. It's a complete kit right down to the last bolt. No researching needed. Just go to Silver Sport Transmissions Web site and fill out the "get a quote" form and they will get back to you with an itemized list with price. Get the close ratio transmission.
Race Director
Joined: Jan 2000
Posts: 13,013
Likes: 2,253
From: Corsicana, Tx
2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
The TKX is great.....but if you've already got 3.08's an alternative is a Richmond/Doug Nash 5 speed. They have a super deep 1st gear and accelerate like having deep rear gears and then it's 1 to 1 in 5th.
I ran one for years in my C2 with 3.36's and it was a nice setup.
They can be found used for low $$$.
JIM
I ran one for years in my C2 with 3.36's and it was a nice setup.
They can be found used for low $$$.
JIM
Safety Car
Joined: Nov 2023
Posts: 3,784
Likes: 794
2025 c3 ('74-'82) of the Year Finalist - Unmodified
https://www.shiftsst.com/?gad_source...53iHewULeMdj6D
Here is the link to Silver Sport Transmissions.
Ordered one of their TKX kits recently.
Here is the link to Silver Sport Transmissions.
Ordered one of their TKX kits recently.
Melting Slicks
Joined: Dec 2009
Posts: 3,220
Likes: 651
From: Thunder Bay
I would get the trans with the .81 fifth gear. The 2.87 first gear will be perfect with your 3.70s. I have the .68 fifth gear and I find it's a bit of a drop from fourth to fifth. It's like a have a four speed with an overdrive, as opposed to having a five speed trans.
Le Mans Master
Joined: Mar 2001
Posts: 6,230
Likes: 1,009
From: Watkinsville, GA and Glen Cove, NY
I second Jim's post, if your automatic car has 3.08 gears. I have 3.08's in my 69 and am running the Richmond non overdrive 5 speed and absolutely love it. Great combination with the 3.08 gears. Very strong transmission as well.