How much work does a 6L80 need to reliably handle 500 Crank HP on a road course?
I've got a thread going in the engine section, but to make a long story short, I'm doing a hot-cam LS3 crate motor swap in my GT after blowing up the L76. Will probably make around 500 HP at the crank when tuned. The car is primarily a daily driver, but I will be taking it to the occasional track day.
Unfortunately, the history of the transmission is kinda questionable. When I bought the car, it would want to surge when coming to a stop. When I had the car dyno tuned by Patrick Guerra, he told me this was because the TCM was running a tune for a stall torque converter, but the transmission appeared to have a stock converter. After he reflashed my TCM, that surge behavior went away. One possibility that comes to mind is that the previous owner had a stall converter in there, and the dealership swapped it back out to a stock unit for resale after he traded the car in. It's also possible that the previous owner blew up the transmission doing drag passes and then had a stock transmission swapped in.
One known problem I had was when the transmission went into safe mode on the way home from work one day. It reset itself after I disconnected the battery, and the problem didn't repeat again. This was about a month before the engine failure. Some forum searching led me to some other people having the same issue every once in a while, and the cause seemed to be a worn out speed sensor of some kind. I will probably have this sensor replaced if I'm getting any other work done to the transmission while the motor is out.
I noticed the transmission shifted at 7000 RPM shortly before I dropped a valve and chucked a piston onto the front straight at TWS. It was NOT in manual mode at the time. This is higher than the max-throttle shift point of 6500 RPM that Patrick programmed, and which the car had been following all day up to that point. I don't know if this is a sign of the transmission being worn out, or just overheating, or what, but I have to assume it was a contributing factor to the engine failure. I did not have an external trans cooler at the time, which was a mistake. I will definitely be adding one after the motor swap. I've looked around a bit, and I haven't decided yet if I want to go the easy route and order the stock GXP cooler from Greg at Pace or go with something a little larger that will require more installation work. Any suggestions as to how big I should go with the cooler?
Anyway, I want to know what you folks would recommend I do to the transmission to reasonably ensure it will handle the extra horsepower when being flogged on a road course. I will definitely be adding a trans cooler, but are there any internal upgrades I can't live without? Can I get away with keeping my stock torque converter? Circle D wants $5k for a full race rebuild, which will be way outside my budget after buying the new engine. I get the feeling that level of upgrade is aimed at people putting down more power than I will be, though. If that's necessary for what I'm doing, then I will probably just have to treat the car nice and stay off the racetrack until I can afford it.
Reply With Quote
Originally Posted by SpaceFrank
...