Whiny differential...poly bushing to cause?

[F34R]

*This thread belongs in both drive train and suspension. I placed here because I am asking about the bushing, as the diff was refreshed*

I refreshed my 2.93 LSD and installed a poly AKG 80A poly diff bushing. I am wondering if it is the cause of the whine when I am not in throttle.

Apply throttle and it is smooth and zero noise, let off and it sounds like a straight cut gear transmission.

It is not adjustable, just a brass sleeve for the bolt. I think it is sending diff noise through out the car from no rubber mount bushing.

Diff was removed but I outlined the relation of the washers to the subframe when I dropped it. Then bolted back up like it was stock. I don't think it has alignment issues.

[F34R]

Jeremy(Monkey Madness) cleared it up fast. Just what I figured was the hard poly was making vibrations throughout the car. Ordering a new OE rubber one, I just cannot stand the howl when I am not in throttle.

[jlevie]

The bushings aren't causing this, but they are making the problem more apparent.

The cause of the noise is incorrect clearance between the pinion and ring gear or incorrect mesh of those gears. I don't know what you did in your refresh of the differential, but if you replaced the pinion shaft seal and didn't put nut back on in exactly the same position pinion preload and thus inion depth would be affected. If any of the bearings were changed pinion preload, pinion depth, and back lash must be properly set for the differential not to make noise.

This can be fixed, but the differential has to come out of the car and disassembled to set up pinion preload, etc.

[F34R]

I stripped it down bare, and cleaned the bearings and installed it all back the way it was. My first time, I guess I made an error.

[jlevie]

If you strip down a differential and don't replace the bearings there are two things that require special attention.

Before removing the pinion shaft nut it must be marked so that it can be tightened to same place to preserve the pinion shaft pre-load. And you must reuse the nut.

Before removing the output shaft bearing hubs each side must be marked so you can return the hub to the same side and position. And each shim must stay with it's hub.

[F34R]

I did make sure the outputs went to the same side. I just tightened the shaft nut with the impact. Should I just remove it and replace the bearings and work from there?

I have a 3.46LSD I want to install from my e24. Maybe I should just remove the 2.93 and change the backing cover and replace the fluid? The e24(auto 635CSi) one has 109k on it and lived in PA all its life. Smooth, locks up insanely quick and zero noise...

[Holland]

Jim is correct, your pre load is off. Your bushing is just emphasizing the noise. My diff makes the same noise, as my pre load is a bit off too.

[F34R]

I made a mistake with the e24 diff...I sold the axels with the output shafts. Am I in trouble with using that one now?

Since I screwed up the preload how/hard is it to resolve it? Annoying the shit out of me driving and makes me worried I am ruining it.

[Robert]

i have a weird noise too coming from my diff, sounds like wind noises. I also have the red AKG Diff Mount.

[pantelones]

I have the same set up (2.93LSD and AKG 80A rear sub-frame set) , and the same noise. When I refreshed my diff, I marked the flanges/shims and even put the bolts back in the same locations. I also matched up the paint (and my mark) on the pinion bolt. Though in addition to a howl, I get a cluck sometimes in 1st or 2nd when I am cruising at low speed and I push in the clutch. Do you ever experience clunking?

[jlevie]

It isn't too hard to set the pre-load, but to do it right you will have to remove the ring gear assembly. Then using a dial type inch-ounce torque wrench you measure how much force is needed to rotate the pinion shaft. The allowable range is 21-28in-oz of torque. If you have overtightened the nut, you'll have remove the flange, replace the crush sleeve with a new part and, then tighten the nut until you have the correct pre-load. To do that you'll have to get or make a counter hold bar that can be fastened to the input flange. Unless you have arms like Superman the tool and wrench will need to be at least three feet long.

You could get lucky and find that you have insufficient preload. Then just tighten it until the rotational torque is correct.

[F34R]

Thank you for the positive information, I am going to use a spare 2.93LSD and try to fix this one back up right.