Does anyone know the max HP the stock auto trans can handle?

 

About 50 less than what the car comes with stock.

 

 

Many variables to this answer. In short, it's complicated. Much of the answer depends on how you use the car. If your out going thru the gears every chance you get, probably 50hp less than car came with, as Kubs posted. Drive it closer to average, with occasional bursts up freeway on ramps will raise the number, really sticky tires will lower the max hp figure, etc. I will say that I have my original 4L60E in my 2000 C5, with a modded LS7 making just N. of 600chp. Trans has a 3,200 Yank converter, and one fluid/filter change, and now has 143,000 miles on it. I've never had any issues.....Yet! Please realize my tuner had to have done something with the trans parameters, and also, afaik, nobody here has had this kind of luck and longevity with this trans, with this much power, for as long as I have had. I either have the best 4L60E GM ever built, and/or my tuner is a genius. I have a unicorn, so dont expect the same luck I've had. Doesnt hurt I'll be 70 in 2 months, but I do take it out and "exercise" it at least once a month. It is literally a crap shoot.....

 

I beat the crap out of mine. Full bolt on with 3.73gears and yank 3200, I’ve done numerous auto cross events along with drag racing at a drag strip, and I’ve done HPDE events, car has 2500 - 3000 road course miles on it, car has a little over 80,000 miles on it, and the transmission is completely untouched except for regular fluid changes and I have an external trans cooler. IMO, drive it like you stole it, if it breaks, fix it.

 

I think the rear diff gears also play into it and how hard the downshifts are vs if you know you are going to give it hell, take it out of drive into 3rd then punch it. Better yet put it in second and roll into it.
Due to only having 4 gears downshifts at wide open throttle at certain speeds beat on the transmission. To be safe I am going with a small cam for a 30-40hp gain. My local tuner said he would not trust anymore than 50hp at most. My car is a daily driver 6 months out of the year with lots of traffic.

 

When I boosted my car last fall, I was more concerned about the torque tube couplers condition than the tranny! I had serviced my trans before I took it in for the SC and it all looked good. Clutch and tranny held up nicely with no slippage on the dyno tune. I do agree, my TCM tune I had done with the SC install (as I had put a 3.42 in the car) makes it shift and work great. Even a stock car, you abuse it, stuff will wear out and break sooner. Let your wallet be your guide!

 

JCMDoug, this is exactly what my tuner told me. He said relying on the auto kickdown is hard on the trans. He told me that after owning the car for awhile, you pretty much know the speeds the car shifts at. He said to manually downshift to the desired gear, based on speed, and go. Since I have 143,000 miles on my LS7 powered A4, with dozens of strip runs, and no problems YET, I'm glad I listened to him......

 

I can tell you my experience with my 1999 Trans Am auto which shares the same ls1 engine and 4L60E automatic transmission. I started with all the bolt-ons such as air intake, long tube headers with offroad mid-pipe, catback exhaust, underdrive pulley and 3500 rpm torque converter. With this setup I was making about 335-340 RWHP and running 12.3 - 12.6 quarter mile times depending on air quality. The 4L60E handled this with no issues and I have hundreds of track passes and thousands of miles driven with zero transmission issues.

Then I wanted more so I added a decent size cam (231/237 112 LSA), fast 90 intake manifold, 90mm throttle body, 4.10 gears and upgraded the torque converter to a 4400 stall. This setup made 395 RWHP on a dynojet and ran 11.5 to 11.8 quarter miles depending on air quality. Within three months my stock 4L60E transmission was fried. I decided to buy a Performabuild stage 3 4L60E that was supposed to be good for up to 1,000 HP. Three months later that transmission failed. I sent it back to Performabuild so they could rebuild it for $500 and that transmission also lasted me only three months. This was only a 395 RWHP car and even a built 4L60E could not handle it.

My personal opinion is if your setup makes less than 375 RWHP then you'll probably be fine. If you go higher, especially 400 RWHP+, then you may find the transmission on borrowed time. I know if I could do it again, I would have either stayed bolt-ons or switched to a TH400 transmission instead of wasting money on a built 4L60E that could not deliver as advertised.

 

That will be the day when I drop my car off at RPM transmission and have them do it. I’m in IL, RPM trans isn’t far.

 

darrensls1, I'll bet you probably had some pretty sticky tires, too. Putting a 4,400 rpm stall converter in that combo would be pretty hard on that 4L60E!! I'm sure some of my luck has been due to 200 tread wear tires, and a 3,200 stall. Still, I have had good luck. Motor made 617hp, and around 530whp.

 

I was running the Mickey Thompson Street radials. They are IMO the best drag radials you can get that are still able to be driven on the streets providing its a nice sunny day. I was pulling mostly 1.6 60' times with some 1.5's if air was good. So yeah, pretty sticky. However, I was pulling 1.6 and 1.7 60' times when I was bolt-on only with the 3500 stall and the stock transmission had no trouble handling that. The more I look back, the more I realize that I enjoyed my car a whole lot more when it ran mid 12's and was reliable then I did when it ran mid 11's and was eating transmissions.

 

I'm scheduled for my A&A kit, 3.42 gears, and Kooks headers in mid-March, so I'm about to find out.

 

The first answer was more honest than sarcastic I assure you. Some people can make them live longer than others.
It’s a good idea to always have a spare when running 4l60 especially if drag racing. Btw I have a stock one out the house if anyone is looking. Lol

 

You sound just like me!! Even though I love the extra power my LS7 has, I enjoyed my car more when I had my stock engine with FBO running 12s. Did that on 315-30-18 Michelin PS2s. So I understand completely.....

 

You have to stay committed to run the 4l60e with any real power to the wheels.

 

i just found out that with A&A t trim , heads, cam,stall that the stock trans is not happy.Considering switching to 6 speed if not a premium auto.Good luck!

 

When we put the A&A and cam package on her last year it lasted two pulls on the Dyno. It only had 36K millage on it.

 

Yep. I already walked through the expected lifespan of the stock tranny with the performance shop, A&A, and the guys at RPM. They all confirmed that even though the later C5 model run stock trannies are built a little stronger, my 2004 tranny will be on borrowed time, but depending on how I drive it, it may last a few years. Either way, I'm ready to pull the trigger on a Stage III or Stage IV tranny from RPM when the time comes which will fortify the entire build from engine back to the transmission and upgraded 3.42 RPM rear differential.

The car was supposed to be in the shop last month for the upgrade but I have a failed lifter so I decided to add a Texas Speed cam and other, better engine components. I'm hoping to drop it off again for the build later this week. I hope the stock tranny makes it past the dyno or it will need be an extended shop layover.

 

I developed the issue of not shifting into 2nd gear until you let off the gas, probably a smoked band.Contacting a guy highly recommended about a rebuild.I got to have some fun with it before this happened,hopefully he can turn it around within a couple weeks .