Rear Suspension Noise

[ericjump]

I just finished going through everything suspension on my 71 240, I'm amazed that almost everything came out great, everything but...

when I drive over a bump, or uneven ground I get a "clunking sound".

Sounds like it is coming from the right rear shock tower, I removed the wheel, put a 2x4 under the drum and pried up on the drum sure enough it sounds like it is coming from the top of the shock/strut assembly.

Here's my question, should I replace the strut mount insulator (page 43, #51, Black dragon catalog), or should I look elsewhere, and should I go ahead and replace both sides? They are 44 years old?

Thanks for the advice

Eric

[Diseazd]

I would tighten the two bolts that go from the diff through the mustache bar. Unless they are damned tight, it'll make a similar sound.

[Patcon]

There is also a rubber part inside the large insulator at the top of the spring that will make noise if its left out (#50 on page 43). On the front there are bearings there, I believe.

C

[Zed Head]

If they really are original, odds are good that they're worn out.  One easy thing you could do is to remove the plastic cover over the top of the strut and loosen the big nut.  Don't take it all the way off because without a gas charge the shaft can drop down inside.  But with the nut loose you can pull the shaft up and down and see if the dampers are shot or not.  You can also get an idea of if things are loose in that area while you're there.  You'll need to get in to that area anyway if you change struts.

[ericjump]

I have just replaced the strut cartridges, the car wasn't drivable before I did the suspension work, so I have nothing to compare it to. In all my reading, I think I have narrowed it down to: #1: Loose bolt/nuts on the rear end to mustache bar, #2: strut cartridges that are not snug in the strut housings, #3: Worn out/ broken strut mount insulator. I'm going after the rear end/mustache bar nuts/bolts first since I won't have to borrow a spring compressor to that.

Thanks for the help, any other thought would be appreciated

Ericjump

[ericjump]

I put 'er up on jack stands and tightened the wizz out of the bolts holding the differential to the mustache bar, took 'er out for a drive and no difference, still the clunky clunk clunk. So I ordered a pair of strut mount insulators, figured while I have the struts out I might as well replace the original ones, they looked good but you know how that goes. I'll let you know how it comes out. Other things I have learned from reading the forum: Check the gland nut is tight and that the shock is held firmly in the strut housing, and that the spring spacer is in place under the strut mount insulator! Wish me luck and thanks for the advise.

Ericjump

[Captain Obvious]

Are you sure that the big nut on the top of the strut shaft is tight? And are you sure the three nuts holding the top of the strut to the body are tight?

 

I'm sure you already checked that stuff already, but somebody's gotta ask...

[Terrapin Z]

Might be a far stretch but the differential mounting isolator will make a clunking noise if the rubber has separated. The sound might travel through the car metal to make it seam like it is coming from the shock tower. It is hard to tell just by looking at it but if you push up on the front of the differential by the drive shaft it should not lift apart at the rubber isolator. kind of a common thing to separate. Worth checking out if you haven't already. Mine was split. I had a clunk. 

[bvolken]

I chased my 'thump' on my '71 240Z for quite a while.  I did have loose bolts that held the diff to the mustache bar.  Just to echo what everyone else has already said, make sure every bolt you can see is tight.

Also, I finally cured the last bump by replacing the leather strap over the nose of the diff with a solid bracket.  I am SUPER PLEASED with the outcome.  You can see my experience here (you have to scroll down a bit): Replacing oil seals R180 differential.

[madkaw]

Check to make sure the gland nut is actually bottoming out on the top of the shock. Another words you might have play between the top of the insert and the nut. Especially if you did not reuse original glad nuts. You run out of thread on the gland nut and it tightens up before it ever touches the insert. Use a washer to close this gap

[ericjump]

OK, after making sure the bolts holding the rear end to the mustache bar were tight, and ordering new strut insulators, I dug into the rear struts to see what was causing my "Clunk" in the suspension. It was only happening when I went over bumps, nothing on accelerating or decelerating. Here's what I found:  I replaced the shocks (stock shocks from Black Dragon) when I rebuilt the suspension, after I removed the strut insulator and the spring, I grabbed the shock rod and it rattled around in the strut housing. I don't know how I missed this when I assembled them. The new shock came with new gland nuts and the instructions said to use the new nuts. After screwing the glad nut down there was defiantly some play between the shock and the gland nut. So here's the fix! I got a large washer that fit into the gland nut, drilled out the center so it would fit over the shock shaft and screwed the gland nut on, amazing the play was gone! I added a "glug" of motor oil to the strut before installing the shock, put it all together and the clunk is gone. Repeat on other side. Thanks for the help with the elusive "Clunk"

A little advice for anyone who is replacing shocks, remove the emergency brake cable before you start, (this will eliminate having to do it while supporting the strut with your knee), remove the brake line where the hard line hits the body and rubber line (same reason), support the strut with a floor jack and lower it down until the strut can swing down out of the shock tower. On reassembly reverse the process (with the floor jack), when the 3 studs won't line up with the holes in the top of the shock tower put a socket down through the center hole in the shock tower and turn clockwise( Tightening the nut) until they line up, jack the strut back up into place attach with washers and nuts.