replacing diff bush

[Jona1971]

My diff bush is split and needs replacing.

I was thinking of replacing it with a powerflex one like this: http://www.ebay.co.uk/itm/BMW-E30-3-Ser ... 19d0570f25

1. as an upgrade?
2. and as its easier to fit. (I don't have a press).

There are several theories of how to remove the old one and I was thinking of removing the diff cover and doing the work off the vehicle.

Is there a preferred method? Any suggestions?

Many thanks,

[Motorhole]

Definitely easier to fit, no special tools required. iirc I removed the old one by cutting through the outer sleeve with a hacksaw then bending it from the cut and knocking it out with a chisel and hammer.

Quite a few people have had problems with the poly bushes slumping, which isn't a good thing at all. I've not had this problem though. I do wonder if its something to do with fitting a poly diff bush whilst retaining rubber subframe bushes - meaning the diff moves around about its body mounting point more than the poly bush can tolerate. If you polybush the entire rear, you may be less likely to have a problem, but I'm not certain this is an 'upgrade' as such. Without a doubt, the best ugrade is a z3m diff bush which is solid rubber, but they aren't cheap. The poly option is much more affordable.

[Jona1971]

Thanks for the reply.
Taking the diff cover off first seems to be the way to do it.

[PG325]

I used a Z3M bush on mine, as mentioned above, diff cover off, hacksaw through the outer metal ring nearly all the way and then force this into the centre to release the hold, it should come out quite easily.

Before refitting the new bush, leave it in the freezer for a few hours, then press it in using a vice.

[bigbird76]

Get the Powerflex black version my m3 chewed one of them up in no time.

Leigh

[HairyScreech]

Don't neglect the beam bushed though. The beam bushes and diff mount work in unison, if one or the other is much harder it greatly increases the load on it. Fitting a poly diff bush with rubber voided beam bushes is going to increase the load on the diff mount significantly as the bush will not flex with the beam bushes.

My personal preference for a road car at the moment is to use standard bushes with the voids filled with 75a polyurethane. This can be bought as 2 part liquid and cast into the voids resulting in something akin to solid rubber bushes that still allow flex.

The rear beam/diff really does need a small amount of movement, there is passive rear steer designed into the system which improves handling if it works in unison with the tyres.

With regard to removing the old diff bush then hole saw the rubber centre out and cut a slit in the metal outer case. The steel case will no doubt have seized to the alu casting.
Make sure you don't cut into the back plate and to minimise the risk cut towards the centre of the plate where the casting is thickest.

[Jona1971]

Many thanks for replies.
I've just had Lemforder replacement beam bushes fitted and it came back with the advisory that my diff bush is split.
I've now ordered the softer purple power flex bush as it's easier to fit than pressing in a new OE one.
I've also ordered a diff gasket from BMW so I can do the job properly - £2.60, a pleasant surprise.
I'll report back how it drives when I fit it at the weekend.