Differential Bush Replacement

[JasonR]

Hi Guys,

I've got a 325I with a sport LSD fitted, laying underneath it the other day and noticed my diff bush is falling apart!

Do i need a press to replace it? Any one know of a 'how to' guide?

Had a look in the Wiki pages but couldnt find anything.

Any help would be greatly appreciated!!

[N00b]

Hi Guys,

I've got a 325I with a sport LSD fitted, laying underneath it the other day and noticed my diff bush is falling apart!

Do i need a press to replace it? Any one know of a 'how to' guide?

Had a look in the Wiki pages but couldnt find anything.

Any help would be greatly appreciated!!

If I recall correctly, it's quite popular to replace it with a powerflex polybush. They come in two pieces and are (apparently) incredibly easy to fit. As far as I know it's not much more difficult to fit an OEM rubber bush either.

[e301988325i]

The best upgrade is a Z3m diff bush from the dealer, the powerflex ones are easy to fit and cheap, but transmit noise and vibration.

A lot of peole burn out the centre, then hacksaw through one side of the steel surround to make removal easier.

Pressing them out risks cracking the back plate which is also easy to crack if the new bush is put in on the piss.

The job really needs a press!

[Brianmoooore]

Fairly obvious, but not a job to try with the backplate still on the car!
Drain the oil, and remove the backplate, and at all times remember that its fragile aluminium alloy. Refit afterwards with a new gasket, and don't forget that a LSD needs the correct oil.

[town325i]

Fairly obvious, but not a job to try with the backplate still on the car!
Drain the oil, and remove the backplate, and at all times remember that its fragile aluminium alloy. Refit afterwards with a new gasket, and don't forget that a LSD needs the correct oil.

what is the correct oil for an LSD?

[Brianmoooore]

Castrol SAF-XJ , IIRC. Probably equivalents in other makes.

[mrcool]

Castrol SAF-XJ , IIRC. Probably equivalents in other makes.

Sounds right, it has a much higher viscoity when at operating temperatures compared with normal difff oil. The W (cold) viscosity rating remains near the same

[JasonR]

cheers for the help! I'm not too fussed about noise to be honest, its for the track, stripped etc. May go for the power flex one if its the easiest.

[leeparkes]

Powerflex ones are easy to fit as they are in two halves and don't need pressing in



My bush removal method is to feed a hacksaw blade through the gaps in the old bush, attach the hacksaw handle then cut through till you 'touch' the alloy on the back plate, remove the hacksaw then tap the bush out

As said back plates can be surprisingly fragile so be carefull

[gareth]

if you cut the sleeve out, make sure the cut is towards the bulk of the backplate, not the outer 'hoop'. then if you cut a bit too deep it won't leave a stress raiser in the aluminium. they like to crack at the best of times so best not to push your luck.

when i remove them, i use a sharp stanley knife to cut the rubber centre out first. hold it carefully in a vice (not between your knees!!!!!!!) and use a large screwdriver through the centre hole in the bush and price the centre off at an angle to stretch the rubber. then cut the stretched part and it'll go through like a hot knife through butter. once it's out, cut the steel sleeve as described above and tap it out.

before fitting the new one, clean any corrosion out of the bore.

a new casing gasket is about £1.50 or less from the dealers. oil can be found for around £20 (2 litres required) from opie oils (oilman on here), and you'll get a zone discount too

[JasonR]

Thanks for all the help, just ordered the bush.
Is the LSD casing stamped with a specific number to ID the correct gasket? Thanks again

[gareth]

a medium case gasket is BMW part number 33.11.1.210.405