Noisy rear diff

[JHZR2]

Hi,

I have a 91 BMW 318i that is kind of noisy. It whines at speeds over approximately 35 mph.

75w-90 and 75w-140 don't work in quieting it down. Nor does using redline diff lubes in those viscosities (common remedy in the BMW circles for noisy diffs).

I am thinking of using redline shockproof heavy, as it gives a film thickness equal to a 75w-250 oil, but has the friction characteristics of a 75w-90 lube. However, apparently it would need LSD additive, and does not have that good of low-temp properties.

Any suggestions? Is shockproof that bad as far as low temp goes (redline tech wouldnt tell me)?

Any other suggestions as to how to quiet a whiney diff?

Thanks,

JMH

 

[c_rossman]

I would check the pinion bearing pre-load, No oil will cure that problem that is destroying your diffy.

 

[JHZR2]

can you explain how to do this?

Thanks,

JMH

 

[c_rossman]

remove the rear drive shaft and jack the car off the ground, You need an inch pound torque wrench to do this and isnt all the accurate with the carrier in the case but its close. turn the yoke and there should be about 10-20 inch pounds of force to turn the yoke (american Motors) not sure what you rig is supposed to be. You may want to check the back lash too. But a loose pinion will cause alot of noise.

 

[MolaKule]

http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=24;t=001349

You posted in two threads!

 

[Ken2]

I'd try Schaeffer's #267 80W-90 gear oil. If that doesn't quiet it, you need a good repair shop. Even if the 267 does quiet it, the differential is likely on borrowed time.


Ken

 

[unDummy]

You sure its the rearend. Hows the CVs/Ujoints/bearings holding up?

Use the shockproof heavyweight.
This will give you plenty of time to drive to all the salvage yards in order to locate the parts that you will need in the future.

 

[mechtech]

I had a 320i that had a differential go out on me, and produced extreme whiney noises.
I drove 15 mile in a snowstorm, and was wildly spinning the tires much of the time. Being a regular, open, rear end, the massive spinning [of one side only] destroyed my spider gears. They were chipped, pock-marked, and lumpy.

 

[JHZR2]

I posted in two threads because at first (this post) I thought surely it was my diff... and so I wanted to see about using shockproof lube in a non-racing app, sine the tech at redline said it has poor cold weather performance.

Since then Ie one more reserch and have found that e30 bmws seem to be very succeptible to damage to the rear wheel bearings due to water contamination, and also that center support bearings can cause similar noises.

Thus my other post attempting to leverage others' knowledge to diagnose the sound.

JMH

 

[MolaKule]

JHRZ,

I wasn't trying to give you a hard time, just noticed two postings.

If the sound is coming from the center of the car, then it might be that the center bearing is dry and going out. Supposedly, they are sealed and lubed-for-life, but we all know every component on has a certain TTF.

 

[JHZR2]

No hard time was assumed, I was just trying to explain myself...

I would really love to know more about shockproof fluids though. Supposedly according to redline they quiet noisy diffs, but then the tech told me I ought not use it in an LSD< and he said that the cold flow is poor, despite claims that it acts like a 75w-90 fluid sin viscosity tests.

Ive been planning to change the center bearing anyhow, since I want to do the guibos for piece of mind. Hopefully that will help. Im having a terribly hard time determining from where in the rear of the car the noise is coming from, and I dont want to put it up and spin the wheels at 40+ mph to reproduce the noise.

If only I felt more comfortable in replacing the diff myself...

JMH

 

[MolaKule]

I would follow Ken2's suggestion, and order some
#267 from salesrep or Bob:

http://www.schaefferoil.com/datapdf/267.pdf

If the diffy quiets down with this stuff, then you will know it's not the center bearing.