4l60e 4th Gear Whine

cwendel4 · January 11, 2011

Alright, I need some help.

I have the new truck in the shop because of popped spot welds and a dealer that hits things when driving in reverse. I took my old 2000 gmc 1500 ext to work and pick up my son from the sitter. five minutes from the sitter the trucks starts to have a a whine/hum. It oscillates and only happens in 4th and when on the gas. Coasting causes the motor to be quiet and if I shift it to 3rd the sound goes away. The sound also changes volume as you go faster, it peaks then quiets. I first thought it was the gears in the rear until I checked by using the Tow/haul button. I had the trans rebuilt about a year and half ago and have only put about 18000 miles on the trans. The truck has also sat for about the past 3 months and was last run on saturday to shake it down before the week.

The sound has the same tone as first gear whine in an old Super T-10 four speed but without the very high pitch of a gear. I hear the hum though.

ANy ideas would be great to know if I am calling the dealer for a loaner since I have to get to work.

Listened again, that hum is the same as and exhaust hum when a pipe is in direct contact with the frame for floor, but not so, checked my self

cwendel4 · January 16, 2011

Alright more info. It truely does happen in fourth only and I would swear I had a bad wheel bearing by the sound when on and off the throttle but the trans is throwing no codes and is storing no codes.

The computer says the TTC slip speed is between 50 and 100 rpm when it shifts to 4th, and it does shift to fourth. Both verified by the computer stating in fourth and I feel the shift and change in rpms. The enhanced data shows the trans runs at about 118 degrees F and that is in 3rd and the TCC slip speed at 2000 rpm in 3rd is under 20. I have been driving it all week in 3rd and have begun to actually like how responsive it is, but I know mileage will suffer and traffic keeps trying to run me over.

Any help would be great. It still has the sound and it does sound like a moan.

I was wondering if it could be the over run clutches as some sites say make a noise in fourth? But the fluid was fine the last time I checked.