What diff?

[Tymm]

I've got bad diff whine, how hard is it to do the output bearings or is it better to get a diff from the scrap yard? if so what diffs can I use ie. can I use a 325 on my 320?

[GuidoK]

replacing the output bearings is not an easy job. First of all they are not seperately sold by bmw, so you have to get them at the original manufacturer (FAG).

Also to get them out is pretty hard, they sit very tight around the diff (you'll need a large hydraulic knive puller (and even then drive a sharp chisel to get the bearing started to move) and some very large C clip pliers to get the 90mm or so c clip in&out).

Also the wine can come from something else (gears, pinion bearing)

I'd go for a scrap diff with some guarantee that you can bring it back if it wines too. Do an oil flush if you get another diff.

You can't get any e46 diff. If you have an 320CI with m52 engine you have a 168diff (thats the size of the crown gear), and afaik they have smaller output flanges (to fit the drive shafts) than the 188 diff.

They also come in different ratio's.

2000 320ci m52: 1:3.35 - 2000 320ci m54: 1:3.38 but later years have lower ratios. As have 325i etc.

Only if your diff is in really good condition (no rust, reasonably low miles), you're certain it's the output bearings, and you're an experienced mechanic with tools (or you can call in help) I'd swap the bearings.

You also probably cant swap the diff without a car lift&transmission jack. It's heavy and the rear bolt is very tight (175nm or so)

Edited August 1, 2013 by GuidoK

[Tymm]

thanks for the info,

so no matter what I'll have to take the diff off?

I was under the car yesterday, 1 of the drive shafts has rotational play at the diff and the other doesn't

my diff had "HG1" on the side

Edited August 2, 2013 by Tymm

[GuidoK]

Yes you have to take it off.

You cannot take the bearing out from the outside. The diff has to come out of its casing.

This is how it looks like:

first use a puller to get the drive flange off:

(not very tight but too tight to do it by hand)

Be sure not to damage the metal dust flange; when it is bent it will scuff against the housing and make some noise.

Underneath the flange is a dust seal (it goes over the C clip). You have to replace that. Maybe it comes with the bearing.

Get the large C clip out (special large c-clip pliers needed):

Now the outer bearing race can come out.

You'd probably have to do this on both sides otherwise the diff won't come out.

With the diff out of the casing you can see the inner bearing:

(the other diff is a quaife lsd)

Get the bearing off using a large hydraulic puller:

My bearing was on so tight that even the puller couldn't get it off; I had to get it started by driving a small sharp chisel between the inner bearing race and the diff.

To get the new bearing on the diff you have to heat it in hot motoroil so it expands and then it slides on (maybe some small taps on the inner race)

Edited August 2, 2013 by GuidoK

[Tymm]

Thanks for the info

would I need more tools to put it back together?

I think it might be easier to get another diff

Edited August 2, 2013 by Tymm

[GuidoK]

Torque wrench (you need that either way).

Also you'll probably need a set of inverse torx sockets to get the drive axles loose.

Another used/scrapped diff is definately easier. Maybe even cheaper (dunno what the bearings cost). But be sure that the new diff is ok and that you have some money back guarantee.

Also with another diff you have less downtime (you can swap it in a weekend or if you're quick in an evening). Replacing the bearings will take 1-2 weeks depending on how fast the new bearings are delivered (first you have to get the bearings out to get the partnumber, then find out where you can order them, then wait for the supplies)

[Tymm]

Thanks for the info mate you've been a real help, I would love to replace the bearing but the part about down time is the deal breaker, I can swap the diff easy in a weekend, I've got free access to ramps, so now to find another diff, just need to find out what diffs I can use, I would like 1 with a acceleration ratio if you know what i mean, but will settle for the same as i've got (HG1)

Thanks again

Tymm

[Tymm]

looking on ebay it looks like my ratio 3.38, there is a 3.46 unit would that be better on accel?

[GuidoK]

According to realoem it's 3.38 or 3.45 depending on what engine you have. But first you have to find out if you have a 168 diff or 188.

This is because that will decide if your drive axles will fit.

Check with realoemcom and your vin# what car/engine you exactly have and what diff.

To check for sure: on the top of the diff casing sits a sticker that has a number on it and the last 3 digits are the ratio.

But you probably cant read that unless you drop your diff...

[Tymm]

I think i've found a replacement diff, i'll find out tomorrow when they open,it is a good scrap yard they only deal with insurance cars. But I was thinking is there any way any thing else will cause this noise and play at 1 of the output shafts? could the drive shaft be goosed? I´m going to go out and try and record the noise.

[Tymm]

Got my diff today, it's from the same year model everything!!! and according to realoem it's the right part number now fingers crossed this works, i'll be doing it this weekend i'll try and do a diy, depends on how things go!!!

[GuidoK]

Be sure to replace the diff oil. You need 80w90 or 75w90 gear oil.

It may be easier to fill the diff with oil when it's (horizontal) on the floor. When it sits in the subframe there's very little room for the usual squeeze oil fill bottle and you may need an oil syringe with rubber hose. At least with the Z4.

This is how much room (z4):

Maybe the e46 has a completely different chassis on that particular point (the z4 has there some beefy reinforcements to hold extra braces that go under the car (sort of strut braces but then for the underside))

But check before you install the diff (or if you have an oil syringe it doesn't matter of course)

If you have a blasting cabinet (glass bead blasting) you can of course refurb the (aluminium) rear diff casing (they corrode like crazy) and the rest of the diff.

It always feels nice to bolt on something shiny and that looks like new. This is what I did with my diff (actually the complete rear axle assembly (complete with all poly bushings), but including the diff).

Old: see above ^^

Refurb:

Nice shiny aluminium and nice shiny new paint

Edited August 8, 2013 by GuidoK

[Tymm]

Thanks again mate

My diff came drained, i've got some 75-90 redline for it, i'm not going to replace any of the seals or gasket as they show no signs of leaks, I have given it a good blast with the wire-brush angle grinder,( not as new looking as yours top job!!!) going to give it a paint tomorrow, what paint did you use? I have also got a lemfoder carrier bush, got a busy weekend!!

[GuidoK]

I used normal black gloss spraycan paint. Not as though as the paint from the factory. But first I cleaned the diff casing with soap, then I used a rust treatment on the cast iron part (phosphoric acid conversion), and then an etch primer. Not that the rust can cause structural damage to the diff of course. It makes sense to replace the diff bushings with the diff swap. Removing the rear bushing can be a pain without the right tools though..

[Tymm]

Woo Hoo!!! got the diff off, I'm now pretty sure the diff output bearing is fubar, you can hear the same noise as i've had for ages and the replacement doesn't make that noise, now time for food a beer and then back out to fit the new 1

[Tymm]

well unless i've got another fubar diff then it's something else still got the noise absolutely no change, don't know what to do next anyone any ideas??????