C5 Advice
Le Mans Master
Joined: Feb 2021
Posts: 6,499
Likes: 4,343
From: Florida
2025 Corvette of the Year Finalist - Unmodified
2024 C5 of the Year Winner- Unmodified
2022 C5 of the Year Finalist - Unmodified
Often it’s not just the components but how they are measured and fit together. Maybe start interviewing trans builders, and start at the top of the food chain. Tell them your history and see what they have to offer.
You’ve hit some setbacks, but you also have an outstanding vision and are so close. It can be exhausting working through something like this. I hope you’ll push through it and find the guy that will make that slushbox eat hp and **** torque.
You’ve hit some setbacks, but you also have an outstanding vision and are so close. It can be exhausting working through something like this. I hope you’ll push through it and find the guy that will make that slushbox eat hp and **** torque.
Last edited by vette4fl; Oct 20, 2025 at 10:50 PM.
Thread Starter
Heel & Toe
Joined: Feb 2023
Posts: 17
Likes: 2
Some odd initial comments up top, but some solid comments as the thread built up.
1200 to 1500 hp. I went up the mountain this summer to see what that means for the first time and learned what I needed to learn. For me, and results may vary, I have a second car as a long-term build project which I immediately realized I have greatly overbuilt. That car being a twin turbo 402 Z06 with a stick. I had had ideas of 550 to 700 rw for street which is easy and manageable, with the concept like you of changing fuels and adding boost to go play at the strip or in Mexico. The SC 427 all E85 coupe is fun as hell at unknown power at 16psi on E85, but that number is solidly north of 850rw at 10psi on 93 pump. As someone said above I immediately realized the car is just unusable for my interests on the street without a significant de-tune. Back down to that 550 to 700 rw range. I offer this only to essentially build some credential in that I've been partly where you are. Your car sounds to be built as a track-only weapon or a rolling start 3am cash cow. There is no street car there otherwise. Right?
So what's the goal for the car when done? Because if it is a track car, there is nothing track oriented for survival about a 4L60E and there should really be no surprise about the carnage experienced.
There are other options than a glide or a 400. But ANY of these options beget the same investment expense which was put into your engine bay. You can't be shooting up and skipping leg day.
So yes, the can mod the car to run a built 8L90 or 8HP70 and any associate controllers and ecus. You can have your cake and eat it too. It just has a steep up front cost which most of us have not had to eat because most street cars here are T56 or 6060 manuals where the only main concerns are the clutch or hydraulics and then the decision on couplers or not. That is a decision for you as well with the couplers and shaft if not already done. And what rear end is in the car currently with expectation of handling "1500" hp?
I'm going to steer clear of giving advice on how to spend your money or with which builder because.... most of these things crap themselves and you are the one who needs to be comfortable with the headache when they do. But if track is your goal, there has been a +$10k glide on the For Sale page for half a year.
I do offer that de-tuning DOWN to sub 700 is a happier place where parts don't break as readily. 700rw is FAST, especially when it hooks. Downright rowdy. Fun all day. Not a blind send, but that happy place of driving it and still getting the adrenaline fix if you're already used to high power.
I hope you solve the problem. I would offer that while many here have offered advice from positions of experience in your situation, you might also turn to other pages for guidance on combos and vendors. specific to your track goal. For what you need, I'm going to aim you at YellowBullet.com
PS - while I don't dig intakes sticking out the hood since it doesn't make sense to me when centri boost is involved, I DO dig the ghost Jake on the plenum. +1
How was that applied?
1200 to 1500 hp. I went up the mountain this summer to see what that means for the first time and learned what I needed to learn. For me, and results may vary, I have a second car as a long-term build project which I immediately realized I have greatly overbuilt. That car being a twin turbo 402 Z06 with a stick. I had had ideas of 550 to 700 rw for street which is easy and manageable, with the concept like you of changing fuels and adding boost to go play at the strip or in Mexico. The SC 427 all E85 coupe is fun as hell at unknown power at 16psi on E85, but that number is solidly north of 850rw at 10psi on 93 pump. As someone said above I immediately realized the car is just unusable for my interests on the street without a significant de-tune. Back down to that 550 to 700 rw range. I offer this only to essentially build some credential in that I've been partly where you are. Your car sounds to be built as a track-only weapon or a rolling start 3am cash cow. There is no street car there otherwise. Right?
So what's the goal for the car when done? Because if it is a track car, there is nothing track oriented for survival about a 4L60E and there should really be no surprise about the carnage experienced.
There are other options than a glide or a 400. But ANY of these options beget the same investment expense which was put into your engine bay. You can't be shooting up and skipping leg day.
So yes, the can mod the car to run a built 8L90 or 8HP70 and any associate controllers and ecus. You can have your cake and eat it too. It just has a steep up front cost which most of us have not had to eat because most street cars here are T56 or 6060 manuals where the only main concerns are the clutch or hydraulics and then the decision on couplers or not. That is a decision for you as well with the couplers and shaft if not already done. And what rear end is in the car currently with expectation of handling "1500" hp?
I'm going to steer clear of giving advice on how to spend your money or with which builder because.... most of these things crap themselves and you are the one who needs to be comfortable with the headache when they do. But if track is your goal, there has been a +$10k glide on the For Sale page for half a year.
I do offer that de-tuning DOWN to sub 700 is a happier place where parts don't break as readily. 700rw is FAST, especially when it hooks. Downright rowdy. Fun all day. Not a blind send, but that happy place of driving it and still getting the adrenaline fix if you're already used to high power.
I hope you solve the problem. I would offer that while many here have offered advice from positions of experience in your situation, you might also turn to other pages for guidance on combos and vendors. specific to your track goal. For what you need, I'm going to aim you at YellowBullet.com
PS - while I don't dig intakes sticking out the hood since it doesn't make sense to me when centri boost is involved, I DO dig the ghost Jake on the plenum. +1
How was that applied?
Thread Starter
Heel & Toe
Joined: Feb 2023
Posts: 17
Likes: 2
option1
The 60e will 1200rwhp but you need to be the one building them and rebuilding them to learn from how it fails over time for about a decade.
The way you use the car will change how the transmission failures occur and in what parts, so personal use and personal failures tailor parts selections and unit & control preferences.
option2
The only other way to use a 60e at that level is to have a literal stockpile of built units from vendor(s) sitting on stand-by in pallets with a dedicated mechanic/shop to swap them out instantly whenever they need replacement. Or be willing to have the vehicle down for days at a time while waiting for replacements (it will not be a dependable car).
otherwise you are simply unable to afford the cost of owning that type of vehicle/use and need to re-think the application.
vendors
The only two humans I would trust to build a 60e anywhere near that level for daily use is Clinebarger (Chris Linebarger) or Dana from probuilt(700r4l60e.com) and even they probably will not warranty a unit beyond say 700rwhp dynojet as it were. The power level restricted by what the vendor qualifies the unit as being capable of, simple as that.
application note1
I've retro fitted several vehicles with Th400 and Powerglides in this situation, But never for daily use or highway use with a V8 app. I would never recommend either for a vette unless it was strictly drag racing and braced correctly for the t-brake/nitrous/tire/diff which justify the fabrication effort of the transmission swap. The glide would be the superior option for a weekend driver garage car(< 1k miles/year) but the engine will be high revs on the highway all the time just to cruise around and I typically don't recommend doing that to a V8, most of the cars I glide acceptably are 2 to 3L engines that don't mind a 3200rpm cruise, low rotating mass in engine/trans can maintain semblance economy and reliability/wear.
application note2
A dependable car would have a mostly stock engine/transmission. My personal opinion based on you wanting to drive the vehicle and unable to afford all the crazy effort required to keep it reliable (option1 and 2 above), you seem like you would enjoy just driving something enjoy the vette. I would sell everything you have there and start over. Use a stock engine this time, an L33 or similar, aluminum v8 stock block. Cam/spring and a small blower 600 to 700rwhp easily gasoline or flex if you can afford the alcohol containment and filtering/supply. Keep it very simple. And a 60e unit from dana at probuilt and done. As long as you can find someone reliable to tune the transmission that combo will go 600-700rwhp dynojet 200,000 miles bet. If you can get an actual PCV system on it and tune it for minimal cylinder pressure and maintain proper oil temps and pressure testing and keeping a low enough IAT.
The 60e will 1200rwhp but you need to be the one building them and rebuilding them to learn from how it fails over time for about a decade.
The way you use the car will change how the transmission failures occur and in what parts, so personal use and personal failures tailor parts selections and unit & control preferences.
option2
The only other way to use a 60e at that level is to have a literal stockpile of built units from vendor(s) sitting on stand-by in pallets with a dedicated mechanic/shop to swap them out instantly whenever they need replacement. Or be willing to have the vehicle down for days at a time while waiting for replacements (it will not be a dependable car).
otherwise you are simply unable to afford the cost of owning that type of vehicle/use and need to re-think the application.
vendors
The only two humans I would trust to build a 60e anywhere near that level for daily use is Clinebarger (Chris Linebarger) or Dana from probuilt(700r4l60e.com) and even they probably will not warranty a unit beyond say 700rwhp dynojet as it were. The power level restricted by what the vendor qualifies the unit as being capable of, simple as that.
application note1
I've retro fitted several vehicles with Th400 and Powerglides in this situation, But never for daily use or highway use with a V8 app. I would never recommend either for a vette unless it was strictly drag racing and braced correctly for the t-brake/nitrous/tire/diff which justify the fabrication effort of the transmission swap. The glide would be the superior option for a weekend driver garage car(< 1k miles/year) but the engine will be high revs on the highway all the time just to cruise around and I typically don't recommend doing that to a V8, most of the cars I glide acceptably are 2 to 3L engines that don't mind a 3200rpm cruise, low rotating mass in engine/trans can maintain semblance economy and reliability/wear.
application note2
A dependable car would have a mostly stock engine/transmission. My personal opinion based on you wanting to drive the vehicle and unable to afford all the crazy effort required to keep it reliable (option1 and 2 above), you seem like you would enjoy just driving something enjoy the vette. I would sell everything you have there and start over. Use a stock engine this time, an L33 or similar, aluminum v8 stock block. Cam/spring and a small blower 600 to 700rwhp easily gasoline or flex if you can afford the alcohol containment and filtering/supply. Keep it very simple. And a 60e unit from dana at probuilt and done. As long as you can find someone reliable to tune the transmission that combo will go 600-700rwhp dynojet 200,000 miles bet. If you can get an actual PCV system on it and tune it for minimal cylinder pressure and maintain proper oil temps and pressure testing and keeping a low enough IAT.
Thread Starter
Heel & Toe
Joined: Feb 2023
Posts: 17
Likes: 2
I work in the performance aftermarket. This is the wrong place to ask questions like this.
If you need and want to keep the power you need to go to a custom shop and have a transmission built. Gearstar, Hughes Coan Racing etc. There are a number of companies out there that can build you a unit that will hold up.
Next have you gone to solid couplers?, Stronger mounts for the rear diff? better gears? Once the transmission is fixed then other stock parts will break.
My question is this. What is the goal? Did you just want a car with big numbers but never really use it? No drag racing is where this mostly would be used. If you track time 650 HP will give you just as fast lap times as you will never use all the power on a road track. Even the GM cars electronics cut most of the power to get the car to hook up.
I would well define what you want and if you really need the power go to a racing transmission builder and detail the use of the car and the engine and get it built to last.
The other option is sell the engine as if it is that good but if you don't need that much and build a lower powered engine that is reliable in the car.
There is no one here that can tell you what to do. You have choices and you need to decide for yourself. I see this at work all the time people build cars that break as they are never done completely. The cars sit and never get enjoyed. You need to get the whole package right and decide how you wan to do it.
If you need and want to keep the power you need to go to a custom shop and have a transmission built. Gearstar, Hughes Coan Racing etc. There are a number of companies out there that can build you a unit that will hold up.
Next have you gone to solid couplers?, Stronger mounts for the rear diff? better gears? Once the transmission is fixed then other stock parts will break.
My question is this. What is the goal? Did you just want a car with big numbers but never really use it? No drag racing is where this mostly would be used. If you track time 650 HP will give you just as fast lap times as you will never use all the power on a road track. Even the GM cars electronics cut most of the power to get the car to hook up.
I would well define what you want and if you really need the power go to a racing transmission builder and detail the use of the car and the engine and get it built to last.
The other option is sell the engine as if it is that good but if you don't need that much and build a lower powered engine that is reliable in the car.
There is no one here that can tell you what to do. You have choices and you need to decide for yourself. I see this at work all the time people build cars that break as they are never done completely. The cars sit and never get enjoyed. You need to get the whole package right and decide how you wan to do it.
Thread Starter
Heel & Toe
Joined: Feb 2023
Posts: 17
Likes: 2
Thread Starter
Heel & Toe
Joined: Feb 2023
Posts: 17
Likes: 2
You're in a tough spot as you need to either commit to necessary supporting parts for that kind of horsepower or just cut your losses and sell the parts and/or car.
I have a cammed and supercharged LS3 with headers in my 2004 C5 convertible. It started as a supercharged LS1, but I hydro-locked the engine as a result of street flooding during Hurricane Debbie. The new LS3 now produces 665 HP to the rear wheels and I know my stock 4L60 A4 is on borrowed time, mostly due to the increased heat. When I originally added the SC to the LS1, I also upgraded my OEM rear differential from 3.15 to a RPM Transmissions re-engineered 3.42 rear differential. When I spoke with RPM explaining that I plan to land around 650 HP, they told me the 4L60 may last five years or it may last five months, all depending on how hard I push the car and how much heat builds up in the drivetrain. I built it for for the street and do not track it and try to avoid hard launches from a dead stop. So far, the temps have been good but when the time comes, I am planning on a RPM Level VII re-engineered trans, a Yank 3200 stall, and a front-mounted trans cooler.
Honestly, I really don't think there are that many good financial choices available to beef up your A4 transmission to manage 1000+ HP and if you really like the car (I love the C5 design), I think you need to ratchet down the HP target, which reduces the heat, which reduces the wear, and you should be able to get a re-engineered (vs. rebuilt) transmission from RPM or the other quality transmission vendors mentioned.
Not driving the car for three years is the hardest pill to swallow.
I have a cammed and supercharged LS3 with headers in my 2004 C5 convertible. It started as a supercharged LS1, but I hydro-locked the engine as a result of street flooding during Hurricane Debbie. The new LS3 now produces 665 HP to the rear wheels and I know my stock 4L60 A4 is on borrowed time, mostly due to the increased heat. When I originally added the SC to the LS1, I also upgraded my OEM rear differential from 3.15 to a RPM Transmissions re-engineered 3.42 rear differential. When I spoke with RPM explaining that I plan to land around 650 HP, they told me the 4L60 may last five years or it may last five months, all depending on how hard I push the car and how much heat builds up in the drivetrain. I built it for for the street and do not track it and try to avoid hard launches from a dead stop. So far, the temps have been good but when the time comes, I am planning on a RPM Level VII re-engineered trans, a Yank 3200 stall, and a front-mounted trans cooler.
Honestly, I really don't think there are that many good financial choices available to beef up your A4 transmission to manage 1000+ HP and if you really like the car (I love the C5 design), I think you need to ratchet down the HP target, which reduces the heat, which reduces the wear, and you should be able to get a re-engineered (vs. rebuilt) transmission from RPM or the other quality transmission vendors mentioned.
Not driving the car for three years is the hardest pill to swallow.
Drifting
Joined: Sep 2022
Posts: 1,431
Likes: 1,096
I knew I had seen it somewhere, 4L80E conversion for the C5...
https://www.corvetteforum.com/forums...onversion.html
https://www.motortrend.com/how-to/09...e-transmission
https://www.corvetteforum.com/forums...onversion.html
https://www.motortrend.com/how-to/09...e-transmission
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Thread Starter
Heel & Toe
Joined: Feb 2023
Posts: 17
Likes: 2
I knew I had seen it somewhere, 4L80E conversion for the C5...
https://www.corvetteforum.com/forums...onversion.html
https://www.motortrend.com/how-to/09...e-transmission
https://www.corvetteforum.com/forums...onversion.html
https://www.motortrend.com/how-to/09...e-transmission
Running Guns & Moonshine
Joined: Aug 2001
Posts: 12,642
Likes: 7,291
From: CT
Nothing is cheap. I think the 6060/C6Z conversions with upgrades must be near 12k now. I'm into mine for half that, but it was early covid time before inflation and I had a working transmission to sell and offset the cost.
Dyno roll on the power which makes a soft hit on the drivetrain. If not, I'd be asking if you're on slicks or radicals since the former gives you basically a spring load as the tire wraps vs the radial sticking which has been known to snap half shafts and shatter cases.
My only other thought or question is what converter is being run and with what settings. And then how the power is being delivered and is it being scaled in or does it come on full st 2k rpm? Details paint the picture, but in the end we still come back to 4L60E and their earned reputation.
I firmly believe and know that if you got a 6, 8 or 10 speed auto in there you absolutely would have a more streetable car since that is a goal. Far more than what is there now.
You might try a larger pulley and/or normal IW hub to drop boost. Or you can apply a different strategy to the BOV(s) through the Holley (I speak Haltech) and control them with an air or co2 tank.
Its the end of the season. You have time to make decisions and hint deals.
Dyno roll on the power which makes a soft hit on the drivetrain. If not, I'd be asking if you're on slicks or radicals since the former gives you basically a spring load as the tire wraps vs the radial sticking which has been known to snap half shafts and shatter cases.
My only other thought or question is what converter is being run and with what settings. And then how the power is being delivered and is it being scaled in or does it come on full st 2k rpm? Details paint the picture, but in the end we still come back to 4L60E and their earned reputation.
I firmly believe and know that if you got a 6, 8 or 10 speed auto in there you absolutely would have a more streetable car since that is a goal. Far more than what is there now.
You might try a larger pulley and/or normal IW hub to drop boost. Or you can apply a different strategy to the BOV(s) through the Holley (I speak Haltech) and control them with an air or co2 tank.
Its the end of the season. You have time to make decisions and hint deals.
Drifting
Joined: Sep 2022
Posts: 1,431
Likes: 1,096
Safety Car
Joined: Oct 2007
Posts: 4,222
Likes: 1,077
From: South Florida
A 4l80e diy rebuild using mostly oem components will hold 800 to 1k rwhp reliably for around 2k in parts including the transmission in a daily driver app (no t-brake/slicks/nitrous)
The problem is, 80e is the worst overdrive ratio unit for a light vehicle on the planet, a heaviest lump of coal the vehicle won't swallow, economy won't be there it goes toilet and handling may suffer depending on height and placement, and with 800-1k you'll be looking for a 3.08 or 3.23 in the rear something like that, dog it off the line with that 2.5, what a mess
I like the idea of more modern units for customers with 20k to burn but personally I would never run something I couldn't rebuild at home easily for cheap, its a catch22 I guess pay to play
The problem is, 80e is the worst overdrive ratio unit for a light vehicle on the planet, a heaviest lump of coal the vehicle won't swallow, economy won't be there it goes toilet and handling may suffer depending on height and placement, and with 800-1k you'll be looking for a 3.08 or 3.23 in the rear something like that, dog it off the line with that 2.5, what a mess
I like the idea of more modern units for customers with 20k to burn but personally I would never run something I couldn't rebuild at home easily for cheap, its a catch22 I guess pay to play
Drifting
Joined: Sep 2022
Posts: 1,431
Likes: 1,096
A 4l80e diy rebuild using mostly oem components will hold 800 to 1k rwhp reliably for around 2k in parts including the transmission in a daily driver app (no t-brake/slicks/nitrous)
The problem is, 80e is the worst overdrive ratio unit for a light vehicle on the planet, a heaviest lump of coal the vehicle won't swallow, economy won't be there it goes toilet and handling may suffer depending on height and placement, and with 800-1k you'll be looking for a 3.08 or 3.23 in the rear something like that, dog it off the line with that 2.5, what a mess
I like the idea of more modern units for customers with 20k to burn but personally I would never run something I couldn't rebuild at home easily for cheap, its a catch22 I guess pay to play
The problem is, 80e is the worst overdrive ratio unit for a light vehicle on the planet, a heaviest lump of coal the vehicle won't swallow, economy won't be there it goes toilet and handling may suffer depending on height and placement, and with 800-1k you'll be looking for a 3.08 or 3.23 in the rear something like that, dog it off the line with that 2.5, what a mess
I like the idea of more modern units for customers with 20k to burn but personally I would never run something I couldn't rebuild at home easily for cheap, its a catch22 I guess pay to play
Running Guns & Moonshine
Joined: Aug 2001
Posts: 12,642
Likes: 7,291
From: CT
Does anyone have a good link with info for this conversion? I have no plans to go auto, but I enjoy learning more tech about our cars and setups when I can.
Burning Brakes
Joined: Dec 2022
Posts: 1,031
Likes: 892
From: Nappytown MD
Running Guns & Moonshine
Joined: Aug 2001
Posts: 12,642
Likes: 7,291
From: CT
Drifting
Joined: Sep 2022
Posts: 1,431
Likes: 1,096
Running Guns & Moonshine
Joined: Aug 2001
Posts: 12,642
Likes: 7,291
From: CT
So really it is custom
Custom Parts Purchases:
Adapter plates fore and aft
Bellhouse for the front plate
Shaft
Custom Labor:
Cut/weld TT housing for new shaft
And then cut the back half of the arm rest tunnel cover to fit
This should be sold as a pre-priced kit basically knowing the parts needed up front for the adaptation. The rest is a cutting wheel and borrow a welder to get the floor and TT done. Not impossible at all. I mean.... it is actually really EASY because all you're doing is buying the right parts to fit. The only part needing focus is how you choose to replace the tunnel plating on the interior and refinish the arm rest area depending on if you want it to be a presentable street car or a race whip.
Not bad. Definitely looks expensive up front though.
