The rear axle carrier – also called cross-member or sub-frame – is attached to the chassis with a pair of sturdy bushings made of metal and rubber. Over time the rubber in these bushings weakens. Some bushings break, others merely sag. The overall effect is that the whole rear of the car feels a bit loose, as if it were moving sideways on its own when you turn. Shifting may result in a loud “clunk” when the clutch is pressed; momentum pushes the chassis forward while the final drive is suddenly decoupled; since the bushings are weak the subframe will jolt and bang against the chassis.
My car showed three different symptoms of mechanical failure in the drive train:
- A loud clunk when I shifted while accelerating, especially from first to second gear, louder when moving uphill – presumably caused by front-to-back play in the bushings. Let’s call this “the big clunk”. This one felt like the car was coming apart.
- A sudden bang when driving over certain small bumps or cracks in the road – probably caused by up-down bushing play that makes the subframe hit the supporting plate or the chassis
- A weak dangling sound when pressing the clutch, as if something were swinging side to side and banging against metal. Not sure what this sound is caused by. I can hear it even if the “big clunk” doesn’t occur. Let’s call this the “little clunk”.
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Since the parts did not come with instructions I emailed both Sir Tools and Zdmak asking for a courtesy copy (it was quite obvious how it worked, but nonetheless). Sir Tools answered a week later and actually sent me a copy by email.
I could have tried to build a similar tool myself, but I just felt like spending the money this time (unexpected bonus at work helped too). Building a tool requires some pipe fittings and caps, a few nuts, a long threaded bolt and a bit of drilling. The sizes of pipe fittings must be carefully chosen to ensure they match the subframe cavity. You can find examples of home-made tools here and here.
Notice the healthy gap between the support plate and the bushing. It will become smaller when the car is back on the ground.
Parts: $45.50 for Lemfoerder bushings on Pelicanparts.com
Time & effort
Around 8 hours – I started at 9:30 AM; the car had its wheels back on the ground shortly before 6PM. This includes jacking up, a short trip to the auto parts store and lunch. Most of the time was spent ratcheting, banging on stuck bolts and in procedures that weren’t strictly necessary. The actual removal and installation of the bushings was a matter of minutes. I can’t imagine how long this procedure would have taken without the special tool. It’s one of the most complex procedures I have completed, albeit less complex than the front suspension upgrade. It was very demanding physically: that evening my hands and forearms were so sore and swollen I could barely turn a door knob. Lifting the glass of beer to my mouth was painful. I hurt until the following Tuesday.
I drove for a few days on steep Seattle streets full of potholes before posting this. I can confidently say that clunk #1, “the big clunk,” is gone. Going over bumps and cracks feels more solid now as well – I don’t get the impression anymore that the rear of the car would fall apart, but this may be just wishful thinking – I have sport suspension, the ride is a bit rough anyway. Clunk #3 is still there, though. Now with the subframe bushings out of the way I can only ascribe it to the differential dangling in the center support bearing. Or something. The quality of ride has definitely improved, but not dramatically.
Do it. If you get “the big clunk” changing the bushings will result in a clear improvement to your shifting. If you decide to do it the barbaric way – removing the subframe entirely, cutting through the bushing with a saw, burning the rubber, taking the cross-member to a mechanical shop to have the bushings pressed in, doing whatever you need to do - it could take much longer, depending on your experience and whether you're working alone or with a helper. Things have been done that way many times and you will find a few write-ups online to guide you. To each his own.