Ok, first off my speedometer is correct. My setup is an (as far as I know) completely stock 4L60E, 3.23 rear and 24.5" tall tires. Im pretty sure the torque converter is stock as well, being as when I stall it I get about 1500 RPM worth of stall speed. Heres my problem, at a 60 MPH cruise with almost no load my tach reads 2100 RPM. This is also with the converter locked out. Another F-body owner in the area has 3.73's in his auto car with a tire thats roughly the same size, and he runs at 60 MPH at about 1800 RPM. My car also turns more RPM in first gear at the same speed as a 3rd F-body in the area with the same 3.23 rear. So, my car just seems lower geared than what it is. One last thing, I know for a fact my car has a 3.23 rear in it. I counted the teeth myself. The tranny doesnt seem to slip ever, even under power. So, my question is whats goin on with it? Were there ever 2 different gear sets in the 4L60E's? Could be slippin a little bit to get me that extra RPM, but not be slipping bad enough to seem like a problem?

 

There is only one factory gearset for the 60. If I had to guess I think your TCC is not working in OD.

 

I'm sorry, but what's TCC?

 

Torque converter clutch.

 

Gotcha, thanks.

If it isn't working right, would it throw a code? When I plug my scanner in I don't get any codes.