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My Z4MC Thread...

"M" Specific discussion
ZAR4MC
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Posts: 64
Joined: Mon Jul 25, 2016 12:58 pm

My Z4MC Thread...

Post by ZAR4MC » Mon May 15, 2017 8:25 am

Hi guys,

So i'm not sure if you guys have ever experienced a grinding noise coming from the rear of your M's when you cold start the car and start driving, making tight left turns?

Mine started to make this grinding sound, it does go away after some few km's but if the car stands for a few hours and you start driving, it grinds on the tight left turns (90 degree turns)... so i decided to replace my Diff oil with Liqui Moly LSD Oil (was very expensive) in attempts to resolve the grinding but it did not seem to help the problem. so after that i decided to use the recommended Castrol LSD oil as i saw most people have used them and their diffs didn't grind so i went out and drained the Expensive LM LSD oil (what a waste) and filled up with the castrol alternative but still it didn't resolve the grinding and at this point i was going to bite the bullet and buy the very expensive BMW Diff oil with the friction modifiers in a final attempt to get this sorted because BMW says you should do an oil replacement using their oil that contains the friction modifiers and it will resolve the issue, there's even a TSB for it. but i did a bit more research and found out that in some cases where bmw replaced the oil, the grinding would come back after some time and then they would then replace the diff (which i was not prepared to do as they are so damn expensive and a 2nd hand one could also end up doing the same). thats where i stopped with the Z4M and parked the car off until we knew what really causes the grinding...

Then my Brother starts getting a really bad grinding sound in the M3 and decided it was time to put her up on stands and go under to have a look...

[IMG]http://i63.tinypic.com/6r4juc.jpg[/IMG]

We (my Brother and I) had to strip out some of these as they where in the wau
[IMG]http://i65.tinypic.com/2zh1pmo.jpg[/IMG]

we had to remove the exhaust to get to the prop. we disconnected it where the headers meet the cats and then dropped it.

[IMG]http://i67.tinypic.com/21bqhao.jpg[/IMG]

We started off with diagnosing her with the following:
> Minor cracks on the Prop Coupling (Guibo)
> Worn down Prop Shaft center Bearing...

So we set out to remove the Prop Shaft so we could replace those two items..
[IMG]http://i65.tinypic.com/s1jf5k.jpg[/IMG]

While under there we checked whatever else we could and then came across some slight play on the side shafts (diff output shafts) and so we decided then pull the diff out and give it a proper check... This is where the fun starts...

Diff out
[IMG]http://i65.tinypic.com/9ut9iu.jpg[/IMG]

Hello LS,
[IMG]http://i63.tinypic.com/2qc1idg.jpg[/IMG]

Started keeping things away in Ziplock bags
[IMG]http://i63.tinypic.com/21az2aa.jpg[/IMG]

A bit more stripping..
[IMG]http://i67.tinypic.com/2e5nkpk.jpg[/IMG]

Boom, LS Core Out... This is where we realize these Bearings Should be replaced and that it made sense for these to cause the Grinding on the Diff... So we set out replacing them... wasn't fun hey..
[IMG]http://i68.tinypic.com/nme1wj.jpg[/IMG]

Old Bearings out
1st one was a learning experience,
[IMG]http://i67.tinypic.com/23msu4g.jpg[/IMG]
2nd one out still in one piece.
[IMG]http://i64.tinypic.com/hwiyk7.jpg[/IMG]

New Bearings on and looking good
[IMG]http://i67.tinypic.com/3451n5t.jpg[/IMG]

closing it up with the new seals in place.
[IMG]http://i66.tinypic.com/9kwduq.jpg[/IMG]

Once the sides where all back together and all bolts Torqued to spec, we gave it an oil flush just to get any metal debris out and then closed up the back over, cleaned it up and double checked everything again to make sure all was torqued to spec.
[IMG]http://i63.tinypic.com/2z4brrs.jpg[/IMG]

Diff Back in place
[IMG]http://i68.tinypic.com/33fbw5i.jpg[/IMG]

Then changed out the old Guibo
[IMG]http://i65.tinypic.com/1z3b9fb.jpg[/IMG]

with a new Guibo and cleaned up the input shaft bolts ready for install
[IMG]http://i66.tinypic.com/2pz0ete.jpg[/IMG]

Then regreased, added a new gasket and Fitted the Prop Shaft.
[IMG]http://i66.tinypic.com/14mvbl.jpg[/IMG]

Heat Shield fitted
[IMG]http://i64.tinypic.com/2cfbd79.jpg[/IMG]

Replaced this broken exhaust suspension mount
[IMG]http://i66.tinypic.com/29m598l.jpg[/IMG]

Even More Torque Specs
[IMG]http://i63.tinypic.com/e5k8kk.jpg[/IMG]

Exhaust back in place
[IMG]http://i68.tinypic.com/i1cyl3.jpg[/IMG]

Almost there.... filled up the new Diff oil..
[IMG]http://i64.tinypic.com/309nix4.jpg[/IMG]

All Done!! and better than before...
[IMG]http://i66.tinypic.com/2cdx1dl.jpg[/IMG]


Happy to report that the grinding is no more!!! the drive train is now smooth as silk 😊

Now to plan this job for the Z4M. It has a different LS Unit but the bearing job should still be the same... will update here with that job.
07 Z4 M Coupe - Sapphire Black/Imola Red

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