4L60E spins in reverse

[Zachsquatch]

Hi folks.
I have an 02 suburban w/ the 4l60e. I was having a driveline noise in 4wd, so I lifted all four wheels off the ground and went through as much diagnosing as my skills and equipment allows. I ran through all the gears and ranges, however when I shifted to neutral, I noticed the speedometer move. Lo and behold the wheels were spinning forward just very slowly. I stepped on the brake and they would begin to move again.

I sit the truck down and it will not move in neutral and I am able to push the truck by hand in either direction.

I checked the fluid and it's still a nice red color and doesn't smell burned up.

All ranges work as they should, otherwise- R, D, etc

My bets are on forward clutch(es) being stuck somewhere, however I'd like to make sure and I'm ready to learn. Thanks.

 

[Dave Sherman]

Probably just some drag in the gearsets that carries a little bit of torque to the rear wheels. My MG, despite being a manual, will do the same thing, simply because the gear oil acts a little bit like a viscous coupling between the intermediate shaft and the synchro hubs.

Edit: Even in an automatic transmission, the clutches often involve a stack of plates separated by the friction material. Just because it's not engaged doesn't mean there isn't some viscous coupling between the clutches.

 

[Silver]

I had a car that would creep forward in neutral at about 5,000 rpm. I always figured it was the exhaust that exited rear and downward but maybe it was this happening.

 

[Jetronic]

Hi folks.
I have an 02 suburban w/ the 4l60e. I was having a driveline noise in 4wd, so I lifted all four wheels off the ground and went through as much diagnosing as my skills and equipment allows. I ran through all the gears and ranges, however when I shifted to neutral, I noticed the speedometer move. Lo and behold the wheels were spinning forward just very slowly. I stepped on the brake and they would begin to move again.

I sit the truck down and it will not move in neutral and I am able to push the truck by hand in either direction.

I checked the fluid and it's still a nice red color and doesn't smell burned up.

All ranges work as they should, otherwise- R, D, etc

My bets are on forward clutch(es) being stuck somewhere, however I'd like to make sure and I'm ready to learn. Thanks.

Perfectly normal if your brakes aren't dragging... it's viscous drag that transfers a little bit of torque. Not enough to move the car but just enough to spin the wheels while in the air. Manuals do it too

 

[mattd]

Unless you notice a problem, it’s likely just gear set drag. Big trucks do that in neutral also

 

[nascarnation]

Back to your noise...is this in 4wd hi range? Is this a new noise?

 

[demarpaint]

I've seen that before as well. If the vehicle drives properly, the fluid isn't badly burnt, it shifts correctly, and there is no delay going into drive or reverse motor on.

 

[MolaKule]

Automatic Transmissions - Drag Torque

Here is an interesting question: Regarding automatic transmission operation, explain Drag Torque.

bobistheoilguy.com

 

[clinebarger]

Did you check the Transfer Case fluid level? Forward Clutch drag is normal on 4L60E's.