Drivetrain "whine"

Buckwheat · May 21, 2017

Hi Folks I have the 2500HD 2002 Sierra 4x4, it is automatic 4 speed 4l80E transmission but has the manual 4x4 shift in the floor. When driving in 2 Wheel High, I get a slight whine from the drive train...sounds like its right below me in the transmission...the noise can be heard with the drivers window down.

It starts at about 20-25 mph( 2nd gear?) and the noise seems to go away at around 40-45 mph (3rd-4th gear?)

It only happens when Im pressing on the gas pedal and immediately goes away when I let off the gas.

There is no hard shifting, it shifts smoothly and the universal joints seem to be ok...no "klunking" etc when forward or reverse or from a stop.

I recently put a transmission cooler on it and changed the fluid that was in the pan and also the filter...the transmission fluid is where it needs to be on dipstick ( in park and warmed up)

Any ideas on this one?

davester · May 21, 2017

It's possible the front actuator is staying engaged. You can check this easily by trying to rotate the front driveshaft (going from the transfer case to the front differential). When in 2hi, you should be able to rotate it by hand.

Buckwheat · May 21, 2017

Hi Davester, when ev erything dries out from all this rain I will crawl under there and check that! Thanks for the information!

Buckwheat · May 22, 2017

Hi I was able to get underneath there after work today. I was able to turn it by hand...I made sure it rotated clockwise and counter-clockwise.

Could this noise be coming from the rear end but sounds like its just below out side the drivers window?

It shifts good through all gears and reverse while in 2 wheel high

davester · May 23, 2017

Are the fluids at the right level for the transfer case, and both differentials?

And as an aside, you might consider doing the pump rub fix if it hasn't been done to your transfer case.

barry G · May 23, 2017

I got noises all over, on amanual.

4 superchargers at the same time, and a large clunky shaft bearing.

it does not reach temps of the auto world...all hard at all times.

Adding a cooler may have changed tolerance a little bit for the better.

No noise is a world of floating make believe.

just had to throw that in there.

Super 8 · May 24, 2017

I actually thought it was my rear end but was told different.

http://www.gm-trucks.com/forums/topic/141631-singing-rear-end/

Buckwheat · May 25, 2017

Hi Folks thanks for the info....the noise stays with the gear changes from about 20/25 mph to about 45 mph.

I didnt notice it before the cooler was added...the cooler does keep it at a lot lower operating temp.

Not too long ago I did check the rear end oil ( drained it and replaced it) after I pulled out the rear axle to replace a rear seal leak on the drivers side...the oil was up to to overflow port....if it will stop raining for a moment I will crawl under there again and check the oil level again in the rear end.....could it be that the oil level dropped pretty good after the seal and fluid was changed?.....I didnt loose a large amount of oil when I replaced the seal and when I drained the rear end oil, the amount I drained was on par with what I replaced.