Hey all, I need some advice on what you would do in the situation I am currently in with my C5. I have roughly 45k into my car overall from wheels up, and yet another broken 4l60 transmission on the very first drive on the dyno, which is the second time this has happened. My car has a setup that should be able to make 1200-1500 on E85, but I'm currently running premium and a conservative tune around 700. The trans is about to be rebuilt again for the 3rd time by performabuilt, and I have yet to be able to drive the car in 3 years.

I am really out of options when it comes to transmissions unless I go to a TH400, which will cost almost 20k in conversion, or an ECS Powerglide for around 9k. The Powerglide seems like my best solution, but I'm worried about being able to cruise around in it. I am told that if I use the right converter with a loose stall, this should help, but I am curious if anyone has gone this route and what rpms they are seeing when driving on the freeway at around 70mph for no longer than an hour. I would also like to mention that I do not care to take the car to the drag strip.

My other option is parting it out and selling everything, and then selling it as a roller. I am looking for some advice on what you all would do in this situation. I have attached a few pics of the car as well for reference.

 

What makes you qualified as an automotive engineer?

What horsepower is the transmission rated for? Same for the torque tube & differential?

Anyone can add engine modifications to exceed the stock performance envelope of the LS1, not many know what the result is on the chassis or the rest of the drivetrain.

 

Who said anything about me being a qualified automotive engineer? The question is what everyone would do, transmission-wise, or would they part it out? The transmission and everything is rated for 900 hp and that is why the tune is set to only 700.

Any c5 owner knows the weak point is the 4l60 and even when built it is glass, dont need to be an engineer to know this.

 

Get rid of it. A car you can't drive is not a car. I would say it's a garage ornament but yours has been in the shop so much it isn't even that.
Dump it.

 

IMO, the 4L60 will never hold 1500 horsepower. I would do the TH400, I’m sure you need a high stall, and maybe like a 3.15 gear with that kind of power. Not sure what cruising RPM would be at 70mph.

 

oh I know it cant hold that much and why im in the situation I am in, To go to th400 its almost 20k

 

Drag car build? Glide.
Road car? Fix the 4L60, and detune even further.

You knew going in that you would be dealing with transmission issues.

 

I’ve been thinking about it and your right, I think I’ll take off the procharger and hi ram and go back to a high 400 low 500hp car that I know should last some time.

 

OP you seem like a dart without feathers lol. I say that jokingly as I don't know you from anybody.

First and foremost, who is doing the work on this car?

If you are paying somebody to do all this and it is just a money pit I would honestly just dump it all and move on to a different hobby.

Looks like a pretty nice build.

 

We need to know where you are sourcing the transmissions, the specifications, builder, etc.

 

please see previous posts to answer your questions. Not sure what that has to do with what I should do?

 

If you are not drag racing the car and it is just a toy than putting a turbo 400 or a glide in it is just a waste of money IMO.

I suspect you are going to have a hard time finding the answer you are looking for. Parting the car out built to this level because of the transmission seems like your heart is no in it?

You should easily be able to find a good 4l60 builder that can make you a transmission for way less than 10k.

 

Well knowing more details would help. You explained the result and that is a good place to start. Clearly you have spent a lot of money, but sometimes the answer lies in small details. It’s possible there are contributing factors beyond the transmission itself.

The previous posts don’t refer to the brand, builder, or specs, and that has everything to do with your issue and what you should do. There are proven builders out there for your hp range documented by posts in this forum alone. I spent ten minutes searching the web and forum and found examples, but it’s pointless to share those without knowing what you have, specifically.

There is a time to spend your way out a problem, but that still requires a well thought out plan. You seemingly have no idea what is causing the failures and finding that out first will help you forge a plan moving forward.

Good luck

 

His original post states who built the transmission.

 

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.

 

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?

 

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.

 

My c5 has a 3.73 gear and at 77mph im at 2600RPM
85mph at about 2800-2900RPM and I think it’s fine.
where would you be with a TH400 and a 3.15 gear, cruising RPM range???

 

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.

 

Caveat: when I suggest detune, I meant to enjoy the car if his goal is street driving. If his goal is track as the engine and his comments seem to be, then Yellow Bullet is where he can learn more of what is going to matter to meet his goals along with the full anticipated power.