Rear end knocking noise
08-27-2020, 11:21 AM
#1
Racer
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Join Date: Jul 2013
Location: New Gloucester, Maine
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Rear end knocking noise
Hi gang. My 85 Coupe has a very noticeable knocking noise in the rear over just about any size bump in the road. Shocks are reasonably new Bilsteins, Rear sway is an Eibach adjustable, also new. I have researched the forum and see that a common culprit is a loose shock mount up top. I looked at the left upper shock mount and the bushing does not appear to be snugged down into the recess like I have seen in other postings/pictures. I can't see the right side , of course, without some disassembly. Few questions...
1. Should the bushing be squeezed tight to the recess as I describe?
2. Is there a torque spec for the upper shock mount, or do you tighten until the bushing is compressed?
3. Do I have to remove the entire air box to get at the right side or just the front half with the air inlet?
Any tips on this would be most appreciated. I thought I would try this first to see if that solves the problem. Thanks, Steve
1. Should the bushing be squeezed tight to the recess as I describe?
2. Is there a torque spec for the upper shock mount, or do you tighten until the bushing is compressed?
3. Do I have to remove the entire air box to get at the right side or just the front half with the air inlet?
Any tips on this would be most appreciated. I thought I would try this first to see if that solves the problem. Thanks, Steve
08-30-2020, 10:11 PM
#3
Racer
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Join Date: Jul 2013
Location: New Gloucester, Maine
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Thanks. I was able to get a 17mm on the nut and hold with an Allen wrench. Cannot move the nut at all. Car is sitting on the ground under normal load. Do I still need to jack underneath the swing arm to relieve tension up top? Wasn't sure if that was necessary when the car was sitting on the ground. Many thanks, Steve
09-01-2020, 01:02 PM
#5
RL Community Team
Rennlist Member
Rennlist Member
It is doable, but uncomforable to get at the right side shock nut with just the forward half of the airbox removed, but it is not much work to take the over half out either... However, in my car I also don't have an AC compressor, which also gives me more elbow room, which may have made a difference in my ability to access that nut.
If the knocking sound persists, take a look at the rear sway bar mounts to the body. This is a relatively common issue. Wevo and Elephant Racing make weld-on replacements that are stronger. You can also do your own reinforcement (assuming the mount is repaired). I did this on my '85 with good results. Here is a link to that part of my project in a thread:
https://rennlist.com/forums/911-foru...ml#post8927525
If the knocking sound persists, take a look at the rear sway bar mounts to the body. This is a relatively common issue. Wevo and Elephant Racing make weld-on replacements that are stronger. You can also do your own reinforcement (assuming the mount is repaired). I did this on my '85 with good results. Here is a link to that part of my project in a thread:
https://rennlist.com/forums/911-foru...ml#post8927525