1983 380SL -- I've got one front lower control arm bushing that is shot (back one on the driver's side). Have ordered a repair kit with bushings, bolt, etc. but want to see if there's a write-up available that outlined just how to replace it safely?
1983 380SL -- I've got one front lower control arm bushing that is shot (back one on the driver's side). Have ordered a repair kit with bushings, bolt, etc. but want to see if there's a write-up available that outlined just how to replace it safely?
My opinion only, as someone who recently replaced the lower control arm bushings...
The only truly safe way to replace those bushings is to take it to the shop and write a check when they tell you how much. Expect large numbers. Short of that, it can be done (I'm not a mechanic) if you take it slowly and take every precaution to make sure the spring doesn't get away from you. That's the big worry - explosive separation of the spring from the control arm assembly. The second biggest worry is having the car come crashing down on you while you're crawling around under it. You'll be removing the suspension so the only thing stopping it from hitting the garage floor is your body. Jack stands are not optional, and that plastic milk crate sitting in the corner isn't an acceptable substitute.
Confession time - I did it the dangerous way. I didn't take the spring out, I just worked around it. I did it that way because I couldn't figure out how it was supposed to come out, and I didn't want to take apart the whole wheel assembly. I did use my rented spring compressors, and I made sure it was fully supported all around. This is the thread I wrote about it:
Jacked up the car and put the jack stands under the jack points on the body.
Chucked the rear wheels so it wouldn't move.
Removed the front tires.
Spent forever trying to wedge the spring compressors (rented from a local rental place) into the springs so I could squeeze them down and get some of the tension off the lower control arm. Finally used two axes and wedged the coils apart far enough to get the spring compressor fingers in place. Insert a phone call to Ike, who kindly gave me his number.
Tightened down the spring compressor as far as I could get it.
Looked at the wheel assembly and decided I really didn't want to take that apart and put it back together again. Grabbed the jacks out of my other two cars and put them in, supporting front and back of the control arm.
Said a little prayer to whatever god/goddess/higher power looks out for people who get in over their heads and took the nut off the first bolt. Said another prayer and used a sledgehammer to work the bolt out. The jacks took up the slack and the lower control arm didn't get away from me. That worked so well, I did it again on the other bolt.
Lowered the car jacks (slowly and evenly) so I had some room to work on getting the bushings out.
Used a crowbar to wedge the control arm out of the socket on the subframe assembly and pulled out two little scraps of metal that used to be bushings.
Heavily greased the outside of the new bushings (lithium grease) and put them into the control arm. Used a C clamp to get the bushings squeezed into place, but they wouldn’t stay, they kept squeezing out again.
Raised the jacks again to start forcing the control arm back into place and left the C clamp on so they’d fit in. I could only go so far with the C clamp in place, though.
Took off the C clamp, continued to raise the jacks. Ran into problems because the bushings were getting stuck on the bolt opening. I tried to work around this for about an hour until I got fed up and used an old wood chisel to pressure the top of the bushing in, away from the upper edge of the bolt hole. It destroyed my wood chisel, but it worked. If I had to do it over again, I’d have gone to Home Depot and bought a couple of sacrificial metal putty knives instead of ruining a $25 wood chisel. Starting the putty knives with the control arm, so they never got hung up in the first place, would have made a lot more sense.
Once they were in place, inserted the bolt in and worked the jacks up and down, liberally applying the crowbar and sledgehammer to get the control arm lined up properly so the bolt would go all the way through. Put on the nut and cranked it down. Then I repeated the whole procedure on the other side of the car.
The front end alignment is done using the bolts/bushings replaced, so I immediately took it over to an alignment shop to get it aligned. It took about an hour for them to get everything within spec. The change in ride quality was immediately noticeable, and the change in the handling of the car was apparent as soon as I got onto the freeway. Once I got proper rims on (I was using wheels with an incorrect offset) it was like a whole different car.
This isn't the recommended method of replacing bushings. It may even be a really stupid way of doing it. I can think of three or four places where this could have gone to hell in a big way, with me in the hospital for my trouble. But it worked for me.
Done...Really wasn't all that bad. One thing I did differently that might have made a difference was that after I had the car on the jackstands, I put the wheel back on, jacked up the wheel a bit and set boards under it so that there was weight on the wheel. This meant that at least one part of the lower control arm was stable.
With the wheel stable, I placed a floor jack and two hydraulic jacks under the control arm. By slowing lowering each jack bit by bit, I was able to lower the control arm safely, the grounded wheel held the spring and arm in the right place...Replaced the bushings and jacked the arm back up into place to put in the bolts.
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