When refitting the propshaft, the centre bearing should be given a degree of ‘preload’. Tighten up the bracket in its ‘natural position until it can just be moved, and then tap it towards the front of the car by just a couple of millimetres before tightening it fully.

PRELOAD

We profiled Redish Motorsport last year shortly after the firm was established and they’re fast gaining a solid reputation for preparing BMWs of all kinds to trackday and full race spec. The workshop is always full of E30s and E36 M3s, while there’s also a long-term E21 project and more than a few E46s on hand too. Our Z3 was a bit humdrum compared to their regular work, but if you want someone who knows their way around making BMWs handle properly, find them at www.redish-motorsport.com or 01179 781 883. And if you’re not located in Bristol, then check out their ‘we pay your fuel’ offer for customers travelling to them.

REDISH MOTORSPORT

Lower axle bush nut: ........140 Nm

Allen bolts on bush

lower plate: ........................ 30 Nm

Lower damper mount: ...... 77 Nm

Differential mount: ............ 77 Nm

TORQUE FIGURES

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PROJECT Z3

PART THREE: WE GET TO GRIPS WITH THE Z3’S WAYWARD REAR END

WORDS AND PICTURES Paul Wager

01First step is to drop the exhaust. You could do this by separating the centre joint but James has learned from experience that a crusty old exhaust is likely to give trouble if you try and get it apart here. As we had the car on a proper workshop lift we were able to unbolt it at the downpipe and take it off complete.

02You’ll usually have to unbolt this exhaust support bracket but on our project Z3 there was no need: it had rusted away long ago! Then unbolt the silver hear shield.

I’ve driven more than my fair share of ropey old BMWs with worn rear axle bushes... but none quite as bad as our project Z3. The Z3 didn’t get the clever Z-axle debuted in the E36 3-Series and made do with a design inherited from the older E30 3-Series, supporting the entire axle subframe on two big rubber bushes located on studs protruding from the bodyshell and when these bushes start to fail, the handling falls off dramatically.

Clearly something needed to be done and a set of replacement bushes was the answer, but on the Z3 the job is nothing like as easy as on the E30. On the E30, the

bush locating studs can be tapped upwards into the interior of the car, but on the Z3 (and E36 Compact) the studs are screwed into the shell from below. This means that you need to lower the entire axle assembly sufficiently to clear the studs and unbolt them to get the working clearance.

It’s fair to say that they do what it says on the tin: these uprated bushes have transformed project Z3 and at last we’re beginning to see some truth in my comment last month that there’s a nice car hiding in there somewhere. The horrible rear-steer feel is long gone and under hard cornering the standard Z3’s squirming behaviour is much reduced too.

Rear subframe bushes

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05You’re now ready to tackle things at the rear end. Before getting too deep into dismantling things though, you’ll need to make sure you can free off the allen bolts holding the axle bush lower plate to the bodyshell. In our case we had to use a blowtorch and plenty of WD40 and it’s a good idea to hammer the allen bit into the bolt head to make sure there’s no chance of it rounding out.

07Disconnect the anti-roll bar drop links from the axle subframe. While you’re at it, unclip the handbrake cables too. Unplug the speed sensor from the differential and separate the ABS sensor wires.

06Assuming you’ve managed to get the lower plate free, your next task is to remove the lower damper bolts. Support the hub assembly while you do this.

08The flexible brake pipes are only just long enough to allow the axle to be lowered by the required 20 cm. We decided to unbolt the brackets where the flexi pipes meet the rigid lines and with enough care, the rigid lines can be eased sufficiently to allow the axle to come down.

03You don’t need to remove the propshaft completely, simply disconnect it from the differential to allow the axle to be lowered. Use a long bar through the universal joint to stop the propshaft from turning and then use a pair of big grips to loosen the clamp on the sliding splined coupling.

04With the propshaft joint loosened, remove the centre bearing and the propshaft can be lowered to rest on the crossmember out of the way.

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11Last thing to remove is the bolt through the differential mount.

13The axle then needs to come down just far enough to clear the locating studs in the bodywork: 20 cm to be precise.

12You’re now ready to lower the axle. With the assembly supported on the cradle, the nuts can be removed from the bottom of the suspension bushes on each side which are all that’s now holding it in place.

14With the axle out of the way, the locating studs can be unbolted from the bodyshell, which will give you the space you need to extract the old bushes.

09Removing the plastic arch liners from both rear wheelarches is essential to allow enough clearance to remove the bushes.

10It’s at this point that we bring in James’s axle cradle, which is identical to the special cradle used by BMW dealers. It sits on a transmission jack and bolts into the lower damper mounts at either side, while supporting the axle under the diff and the trailing arms. Crucially it allows the entire axle subframe to be lowered safely and evenly,

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17These are the replacement Powerflex bushes which are really worth fitting considering the work it takes to get this far. Not only are these polyurethane bushes firmer than the original ones and so will sharpen up the Z’s handling, but they’ll last forever.

19With the Powerflex bushes fitted on both sides, the mounting studs can be refitted and the axle can be raised again.

18The Powerflex bushes have another important advantage too: they can be fitted by hand without needing a special tool. They’re in two parts: the bigger lower bush which goes inside the axle tube and an upper piece which sits above the axle. The metal tube runs through the centre of the bush.

20You’ll need to correctly torque up the M14 nut on the bush locating studs to 140 Nm. All you need to do now is replace all the parts you removed earlier.

15To extract the bush neatly, you’ll need a special tool - even with the right kit we had to use plenty of heat to get the bushes moving. If you cut the bushes, don’t cut into the housing. Borrow or hire the proper tool - TBMW advertiser Phoenix Motorsport hires out several special BMW tools. Find details at www.phoenix motorsport.co.uk or 01276 27711.

16Here you can see how the special tool works. The threaded central shaft is turned to pull the bush downwards, while the serrated legs grip the tube in the axle subframe.