Thread: New transmission not working correct - possible PCM issue?

Originally Posted by Trannyman95

If you truely have a 33 Drive and 37 Driven then your builder went in the wrong direction!!! This will give you a 3.69 overall ratio. The HD transmissions have a 37 Drive and 33 Driven, giving you a 2.93 overall ratio. The GT / NA 3800 cars had a 35 Drive and 35 Driven sprocket arrangement. Again, PLEASE check the current gear ratio on a scanner in 3rd gear, there is nothing more to talk about until you check that number unless your builder admits to putting in the wrong gears, which will be proven with a scanner.

Trannyman95. You were correct, my math was wrong. They did put in a 33 Drive and 37 Driver for a 3.69 overall ratio. The builder gave me the option of changing out the gears or putting in a new PCM from zzperformance. I went with the new PCM, because I kinda like having the stronger acceleration with the new gears. Everything is working perfectly now.

Originally Posted by Trannyman95

Glad to hear you got it sorted out and everything is working right now

Trannyman95... there is one odd behaviour that I am assuming has to do with changing the stock torque converter with a 2800 stall torque converter. When cruising on the highway at 60 miles an hour... at the slightest change in grade (going up hill and I do mean slightest) it seems the transmission slips because the revs will go up about 500 rpm for about a second and then back again, and I can feel the car get weighted back. It will continue to do this untill the grade levels off again. Is this PCM again or something else?

Originally Posted by Trannyman95

If it is not a stock / OE converter then it likely doesnt have the correct woven carbon lockup clutch lining and isnt holding like it should. Most aftermarket pcm suppliers up the TCC duty cycle to overcome this. It is normal opperation for the rpms to come up a bit and the pcm will catch this and quickly up the duty cycly of the tcc solenoid to drop the slippage to a desired level but if it seems a lot farther off then it did with the stock trans then you will likely need to make some adjustments to the tune.

Specifically, what would I adjust in the tune?