DIY: Rear bushings lube for suspension noise

[santov]

I've had my Z4 for a couple weeks now. But every time I went over a speed bump or up a inclined driveway I'd hear a ton of groaning from the right rear. What's worse is my own driveway is at an angle so I get to start and finish each drive with the obnoxious racket.

I searched the forum and found a few posts on aftermarket bushing kits and I know that the rear sway bar bushing bolts come loose, but I didn't find any articles on noise.

The design of the rear end is amazing. The fit and finish of the components and how the link goes through a window in the upper control arm, it shows this car was well engineered. Sadly I think BMW used bushings made of softer rubber instead of the stiffer (and quieter) poly-urathane, perhaps for ride control, maybe to save money. I considered spending the day taking the rear end apart, but was quickly discouraged by the amount of work it would be. I had plans of taking the bushing bolts out, and lubing with Shin-Etsu grease. It's the same grease that Honda uses on seals, door hinges, seat tracks, etc. The grease is safe for rubber and lasts forever. Instead I used Heavy Duty Silicone spray. I didn't want to since the silicone can wear off and leave the rubber or plastic even more dry and "creaky" than before, but I was at my wit's end.

I started by lifting the car, dropping the pan, setting on jack stands and removing the tires. Now that I think about it you could probably access all of this with the tires on and just lifting one side at a time. Be safe and use jack stands or ramps.

I sprayed the following on each side:

• Sway bar brace bushing close to rear diff (it's really soft rubber, and I suspect the main offender)
• Sway bar end bushing [top of link arm]
• Sway bar link bottom bushing
• Lower control arm under hub
• Upper control arm behind hub
• Lower control arm close to diff
• Upper control arm close to diff
• Black stopper at top of spring
• Black plate underneath spring
  **NOTE: There was a ton of sand and road grime on the plastic pad that sits under the spring. To clean the embedded sand out I sprayed with Simple Green then used my air gun to blow all the junk out.

After I did both sides I used the jack to compress one side by about two inches. Then sprayed all the spots again.

I lifted the car off the jacks, put the pan back on and went for a test drive.

WOW!! The car doesn't creak at ALL. I even went over a tall thick speed bump at a 45 degree angle one tire at time angle to see if I could get any noise. Backing up my driveway it's dead solid quiet. Ahhhhhhhh!

So if you have any creaky, clunky noise try lubing the bushings. I think after I'm out of my warranty period I'll look into a performance aftermarket set, but for now I'm really happy. I'll report back on how long the silicone lasts. If less then a few weeks I might try a dry film lubricant that's safe for rubber.

[wildag]

FYI, poly-urathane is certainly not more quiet than the OEM rubber bushings. Ask any Z3 owner with aftermarket subframe, or rear trailing arm bushings.

[thekurgan]

Might not be a good idea to use any lube on the bushings, they will attract a lot of dust and dirt and increase the wear. Sounds like you should have the bushings replaced, maybe with the powerflex if you're looking for a longer lasting bushing?