Auto trans swap options?
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Joined: Mar 2026
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Auto trans swap options?
What are the current best accepted swaps for a 4L60 or is the best bet to just stay with the 60 and build it out?
Obviously, the goal for the car is street strip, big converter manual valve body doesn’t scare me, but it appears the options are limited?
Obviously, the goal for the car is street strip, big converter manual valve body doesn’t scare me, but it appears the options are limited?
Running Guns & Moonshine
Joined: Aug 2001
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From: CT
I detest 4-speed autos of yesteryear. That is well known of me. I could never justify the expense and headache of a TH400 built for a C5 vs an 8L90 or 8HP.
An 8L90 is a different beast and entirely worthy. That is having your cake and eating it too.
I would be curious how they get the slappy paddles to work in a C5. I wager a BT feed from some paddle functions out to a reader then to the trans canbus. What are they using to run the 8L90 itself?
An 8L90 is a different beast and entirely worthy. That is having your cake and eating it too.
I would be curious how they get the slappy paddles to work in a C5. I wager a BT feed from some paddle functions out to a reader then to the trans canbus. What are they using to run the 8L90 itself?
Tech Contributor
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From: Dyer, IN
Options are limited in what respect?
Tech Contributor
Joined: Jan 2007
Posts: 19,390
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From: Dyer, IN
I detest 4-speed autos of yesteryear. That is well known of me. I could never justify the expense and headache of a TH400 built for a C5 vs an 8L90 or 8HP.
An 8L90 is a different beast and entirely worthy. That is having your cake and eating it too.
I would be curious how they get the slappy paddles to work in a C5. I wager a BT feed from some paddle functions out to a reader then to the trans canbus. What are they using to run the 8L90 itself?
An 8L90 is a different beast and entirely worthy. That is having your cake and eating it too.
I would be curious how they get the slappy paddles to work in a C5. I wager a BT feed from some paddle functions out to a reader then to the trans canbus. What are they using to run the 8L90 itself?
Tech Contributor
Joined: Jan 2007
Posts: 19,390
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From: Dyer, IN
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Running Guns & Moonshine
Joined: Aug 2001
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From: CT
For back in the day, running around with screaming converters and high rpm and poor gear selection on the street was a price to be paid for relative consistency and strength. That is no longer the case. Now you can have a strong unit with decent gears and overdrive and a car which can be your grocery getter AND your track whip. If both kits ballpark similar expense and customization then there is only one direction for me. Owning a 3 speed on anything short of a dedicated track car today is entirely outside my interest. Particularly on a sports car. I've had them. Never again. That's just my opinion a D where if send my money.
For anyone building a car and ever planning to sell it, I wager the 8L90 is the easy sell too.
For anyone building a car and ever planning to sell it, I wager the 8L90 is the easy sell too.
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From what I was seeing early in my search, undercarriage space mostly. Let's face it you don't see it done with very many different combos. Can anything be done with enough money and fabrication skills yes. I have swapped to RMVB 400s in other vehicles and I personally love how they drive. To each their own I suppose.
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From: Dyer, IN
From what I was seeing early in my search, undercarriage space mostly. Let's face it you don't see it done with very many different combos. Can anything be done with enough money and fabrication skills yes. I have swapped to RMVB 400s in other vehicles and I personally love how they drive. To each their own I suppose.
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I don’t know. I was looking at options outside of the 4L60.. but it sounds as though RPM probably has the lockdown on some quality 4L60 options Probably 1200hp in the long run. I’d like to build for the future not for the year if possible. Based off 6 to 10 transmissions over the years, I’m much prefer a TH 400 in a reverse manual valve body for numerous reasons. Which you likely already fully understand.
Burning Brakes
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Race Director
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From: Central TX
C5 of Year Finalist (appearance mods) 2019
I don’t know. I was looking at options outside of the 4L60.. but it sounds as though RPM probably has the lockdown on some quality 4L60 options Probably 1200hp in the long run. I’d like to build for the future not for the year if possible. Based off 6 to 10 transmissions over the years, I’m much prefer a TH 400 in a reverse manual valve body for numerous reasons. Which you likely already fully understand.
C5's came with 4L60E transmissions, not 4L60's.
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Yes, 4L60E and 4L60s are not exactly the same. Also, IIRC, the 4L80E WILL NOT FIT without cutting the floor up, which is what I think Lucky was getting at. OP-Just my opinion, but why not run stock trans until it starts slipping or a gear disappears? My stock 4L60E has lasted me 150,000 miles, and there's been a built 427 yanking on it for the last 90,000 of them. Another thing to consider is even though the TH400 and 4L80E are pretty much bulletproof, they absorb more power to drive them. Plus they require floor surgery to fit. My .02...
Last edited by grinder11; Apr 28, 2026 at 08:36 AM.
Tech Contributor
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From: Dyer, IN
With a target of 1200 RWHP, that car is getting cut up if that power is getting to the ground. Some serious fabrication is in the future.
Race Director
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Yeah, 1,200 whp would probably be too much for the stoutest 4L60E. A lot depends on what tires he runs. One thing that really helps the 4L60E survive when built is the relatively light weight of the C5....
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I'll also add that the entire powertrain will need some of the best, most expensive parts $$$$ can buy if you're pushing those power numbers. EVERYTHING will need beefing up if retaining the IRS setup....
Drifting
Joined: Jul 2004
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From: Pingree Grove IL
I prefer a car I can drive everyday. I’m not going to drive a 1200 horsepower C5 to work and back everyday. But give me an engine like @grinder11 , a nice 500-550 wheel and drive it 100,000 miles, now that’s enjoyment, IMO. A stout 4L60E that can handle the power is fine with me.
