I got one for you thinkers out there

[4xquadrod]

I put truck in reverse and had a bad vibrating shutter. Thought it was the trans, so we pulled the pan to check the reverse band adjustment and it was fine and nothing in the pan. Hooked up a line pressure gauge and stuck it in reverse pressures started at 200psi and climbed with throttle. So we decided it might be in the rear end. When I powerbrake in reverse there is no shutter but as soon as I let it roll it shutters like a clutch is chattering sort of.

Pulled the rear diff cover and found one little metal shaving and nothing else. The oil still looked clean and nothing in the bottom of the houseing. Heres the weird part (at least weird to me) If I put the truck in 4 wheel I can back up with nothing going on. As soon as I back up in 2 wheel it screws up.

We are now thinking maybe something with the ABS system?



Any thoughts



Steve

 

[rbattelle]

ABS is an interesting theory. What about some strange binding in the driveline? You say it's fine if you don't actually move the vehicle. Of course, the 4wd thing is odd, but I know for a fact that ABS is still on in 4x4 mode, so that partially eliminates the ABS as a culprit.



Broken tooth on the ring gear?

 

[bombero]

How about a front drive line problem. Its turning when you put it into reverse even in 2wd. Maybe when you engaage 4wh it firms up?? Just a thought

 

[Briman]

Your sig says that you have 3" spacer lift. Is it a body lift or blocks under the rear springs? When I back up my stock truck I notice the spring wrap quite a bit more than going forward. It's worse when backing up a hill. Your large tires may amplify the axle wrap as well. I'm just guessing... ... I don't see any traction/ladder bars. Three inch blocks would exaserbate (sp) the problem.



If this is the problem, going to four wheel drive could indeed stop it (unless spining the tires) because of the four link front pushing you back.

 

[JMingledorff]

It could be as the springs wrap a little the u joint begins to bind a little. When in 4 the axle isn't going to wrap near as much. I'm guessing that the rear is lifted a little. Does the rear end make any noise at all. Could have something to do with the pinion bearing. Have you looked at the pinion angle?

 

[4xquadrod]

I have a 1" spacer in the rear and it has been there for 38000 miles with no problems. I put my truck on my lift and placed it in reverse and when I applied my brakes it sounded like a loud racheting sound. Maybe like a light weight metal pipe being draged along a metal picket fence. Sort of like some gears were trying to engage.

I also pulled the rear diff cover and the ring and pinion look fine.

The noise seems to be coming from the rear area.

 

[rbattelle]

I just thought of this: check the parking brakes!! They're drum brakes inside the center section of the rear discs. Of course, that doesn't explain why it goes away when in 4wd, but it's something to check out anyway.

 

[4xquadrod]

We might have it isolated to the limited slip in the diff.

 

[Russknh]

Well don't waste any more time cus I can tell you what it is--it is the gear vender od unit, I had this problem many times when I tried to run one with an exhaust brake--give them a call and they will tell you to send it to them for rebuild

 

[4xquadrod]

Gear Vendors

I drove my truck over to gear vendors and left it. (I work close to them) They installed a new unit under warranty and will tear the damaged one apart to see whats up.
They told me when towing be easy on it when I am in reverse.

Thanks Russknh.

Steve