i think i may have problem with my differintial

[ACHTUNG]

so then i can just go and pull one out of a 318 or anything like that and check the bolt patterns

Here is a thread on E30tech.com that shows which diffs came with each e30:

http://www.e30tech.com/forum/viewtopic.php?t=1901

[crazynoll]

so then i can just go and pull one out of a 318 or anything like that and check the bolt patterns

[Silence*]

e21 was the 3 series previous to the e30. a e28 is a 5 series from the late 80's.

[crazynoll]

yah its only been like a week and half since ive changed the fluid in it. but ive been thinking to the diff swap just for the upgrade. i wanted to know what car i should look for when i go to the junkyard. i still dont know
what to look for when people say e21 or e28 is that like 321 e or something like that sorry really dumb ?

[Mike325]

I believe you also need to swap the output shafts. e21 ones are a different size.

But isn't the e28 diff a swap cover only type deal?

[AndrewBird]

I believe you can get an e28 diff and put the rear cover from the e30 diff onto the e28 diff and that will then bolt to your car.

I believe you also need to swap the output shafts. e21 ones are a different size.

[Mike325]

If the noise is speed related, the pump would not be it. The noise would happen even standing still. The diff fluid needs to work itself into the diff. Give it 500 miles or so before you take the diff out.

To answer your diff swap question. I have an eta as well and I took out the 2.93 diff and put in a 3.73. The car pulls harder, but the rpms will be higher on the highway and with just normal driving. I believe you can get an e28 diff and put the rear cover from the e30 diff onto the e28 diff and that will then bolt to your car. I would recommend the 3.46 or a lower gear if you want to keep the good mileage of the eta.

[jlevie]

This sort of noise can also be from a fuel pump. Before diving into a diff rebuild or replacement it would be a good idea to make sure you are repairing the real problem.

[crazynoll]

i changed the fluid and the noise never went away and found out that its the out put bearing. so i guess im just going to swap out the diff and put an lsd one in.
anyone know what gear ratio i should go with or what cars i can pull one out of at a junkyard.

[ivo316]

If you added fluid and it didn't go away, and you are positive it's the differential (as in a friend lays on the back seat while you drive and he confirms it comes from that area), then you have three possibilities.

1) Replace your differential with a good one.
2) dissasemble and check what's wrong, sometimes the ring gear is not perfectly aligne with your pinion, that's a bitch to get right, also if you have driven like that for too long, even if you fix it the wrong wear will make it sound anyway.
3) Replace ring gear and pinion with new or matched ones.

DO NOT under any crcumnstance replace just one part, the noise might even get wose.

Before all this please verify all the bearings in your rear end, maybe it's a shot bearing and the sound is being transmitted all over the rear end tricking you into thinking it's the differential.

Good luck

[crazynoll]

and the noise didnt go away

[87-325ic]

mine does this too, its a steadywhine especially when up to speed..

i aready changed the fluid with redline too..

is it the coldness here? im in NC

[crazynoll]

thanks alot ill do that asap and yah im sure its not enigne speed related u can definitely hear it coming from the back

[ivo316]

If it sounds just like when you drive backwards it's the differential, go to a lube center and have them add oil, if it doesn't stop, try a teflon or molybdene additive, if it still does not shu up, learn to live with it until you fix it or replace it.

[euroshark]

Is it for sure car speed related, and not engine speed related? Belts can make that noise, so can a bad PS pump or water pump.

Its not terriblly hard checking the diff fluid level. Remove the filler "bolt" near the top of the diff and shove your finger in the hole. If you don't feel fluid, you probably need some.