Hey everyone I have an 04 2500hd with 4.10's and a 4L80E, its also got 285/75/16's on it. I have been noticing my tranny to be acting a little funny, now driving around it seems to be a little high in the rpms to keep a constant speed of 45-50mph. I was wondering what others are doing RPM wise around those speeds? It has a superchip programmer in it just to correct the speedo.

Thanks a lot
71 Rat

 

Those tires are about 33" in diameter, so...

88/((33x3.14)/12)*4.10*.75*50 = 1566 RPM in fourth gear with the converter locked. If it's more like 2089RPM at 50mph then you're either in third or the converter isn't locked up.

 

thank you for the math and the responce, i was noticing around 2 grand around 45-50 so i guess its normal. ohh well one day I'll just get a built 80e Thank you again for the math and the answer

 

Glad it is within spec.

I have had a shift soleniod go out and the trans would not shift into fourth (or first). the PCM would report the trans to be in forth but the converter to be sliping...