I have done the search on this board and have only found many suggestions but nothing repetative. I am checking to see if anyone can put a definate finger on the source of the noise.

I have the pretty typical problem of a grinding noise from the rear when you let off the gas and let it coast and it goes away again when the throttle is picked up again. You can even feel a vibration on the tunnel between the rear seats. It also seems to be there, but very faint, when it cruises steady down the road.

It is a rear end that I just swapped in and never drove before. It sat for a few years unused and for awhile with no oil in it. Some of the teeth did get a slight rust build up. I have no reason to think it was disassembled beforehand.

Where is the source specifically? The meshing of the gears, bad bearing, etc.?

 

try pulling the cover and inspecting it and you'll know exactilly what it is.

 

How's that? If it's a bearing, how will I see that? I can see the teeth might show something in the pattern.

I just had it apart before I stuck it under the car. Nothing stood out except for the slight rust.

I am looking for more than a suggestion. Something definate that someone else has found in the past that caused the noise.

 

Sounds to me like either a bad rear U-joint, or a loose pinion nut.

 

bearings, bad gear set, bad u joint that's pretty diffiante. take it apart and start inspecting it. if you can't tell a bad part when you see one take it to someone that can.

 

I'd inspect and/or replace the U-jopints before I take apart the rear end. Start with the cheap parts first, then work on the more expensive and more work intensive parts.

 

Same driveshaft that I was always using, so I know that was not it.

So if it is a loose nut, is it at the teeth where the noise is originating or from somewhere along the pinion shaft?

This rear spent its life doing year round duty in the saltly upper midwest so it is covered over with rust. I can't imagine any nut coming loose. I could barely free up the ones I wanted loose. I will check this first.

The point of my post was to see if I can avoid having to tear it all apart and looking into every detail. That is why I was asking for something very specific, not all things. If it is a loose nut, I won't have to take it all apart.

 

if it's a loose nut you'd have to take it all apart, unless you want to halfass it back together. ok maybe not all apart but apart just the same.

 

be careful
before you take the pinion shaft nut you should
1-Matchmark the driveshaft and pinion yoke so they may be reassembled in the same position.
2-Use a punch, mark the position of the pinion yoke, pinion shaft and nut.
3-when you gonna install the nut back make sure you tighten an additional 1/8" turn beyond the marks.
Good luck

P.S. Like what other people said it could be U-joint or
Pinion shaft's nut is loose

 

The doctor has returned! My diagnosis - loose pinion nut. That pinion was floppin' in the breeze. Can't hardly believe it but it is so. There must have been some grease on the nut to keep it from being a victim of rust. It is official, if you have this noise like this, check for a loose pinion at the nut.



See, I got to find the problem without taking it apart. Tightened it up, took it for a ride, noise gone. Fast and simple diagnosis. NOW, I can take it apart and rebuild it knowing the problem will not return. I have done the "halfass" method of spending a day working on something, not for sure of the problem, only to still be right where I was to start with. Keep the horse in front of the cart. You could end up wasting time and money and not have had to. Been there.