260Z Rear Suspension Banging

[Captain Obvious]

And forgot... Looking at the different heights of those insulators, it's easy to imagine that there may be a difference in the length of the necked down portion of the insert shaft to accommodate the difference.

[SteveJ]

1 hour ago, Jeff G 78 said:

If that fails to provide answers, have someone drive the car over small bumps while you listen to a stethoscope with the end on the top nut of the strut.  You should be able to confirm if the noise is coming from the strut or elsewhere. If that too fails, Chassis Ear will be needed.  They are the same as a stethoscope, but are wireless and can be attached to various chassis parts so you can listen while you drive over the proper input.  The noise can be isolated to a specific component rather than knowing that it's coming from the rear of the car.  Chassis Ears are about $100 for a basic setup.  https://www.amazon.com/STEELMAN-06600-ChassisEAR-Electronic-Squeak/dp/B000IHIAES/ref=sr_1_5?crid=2K7L0ZJIEUAHF&keywords=chassis%2Bears&qid=1645206093&s=automotive&sprefix=chassis%2Bears%2Cautomotive%2C139&sr=1-5&th=1

Dang it! That's another tool added to my Amazon wish list.

[Jeff G 78]

3 minutes ago, SteveJ said:

Dang it! That's another tool added to my Amazon wish list.

Me too.  We have used them at work for years.  They used to be wired which was a bit of a pain near spinning components.  I'm curious if the commercial version and the consumer version give similar quality.  

[heyitsrama]

From my records I used KYB 361001 and 361002 on my early 260z chassis. @Randalla you got a photo of the gland nut? Mine also did the same clucking sound and it was a loose nut allowing the strut casing to shake around in the strut tube. I've also experienced what Steve was talking about with a loose strut bar connector, but it was only over speed bumps.

[Zed Head]

There is a substantial difference in length between short tower (240Z) rear shocks and tall tower (280Z) rear shocks.  A short strut in the tall tower tube would let the gland nut crank all the way down and the insert clank around in the tube because it would be hanging free.  That would be an early insert in a late model tube.  You can tell early versus late by the height of the rear shock towers inside the car.

36001 is short and 36003 is tall.  You would not be able to fit the nut on a 36003 in a short tower strut tube, it would stick out of the tube too far.  

https://www.rockauto.com/en/catalog/nissan,1976,280z,2.8l+l6,1209226,suspension,strut,7584

https://www.rockauto.com/en/moreinfo.php?pk=502600&cc=1209226&pt=7584&jsn=702

https://www.rockauto.com/en/catalog/nissan,1973,240z

https://www.rockauto.com/en/moreinfo.php?pk=502428&cc=1209170&pt=7584&jsn=652

Look at the wheel well bump compared to the strut tower.

https://bringatrailer.com/listing/1972-datsun-240z-222/

https://bringatrailer.com/listing/1978-datsun-280z-119/

Edited February 19, 2022 by Zed Head
+ tube

[Randalla]

Correct struts are ordered. I'll report back here on progress and results in a couple of weeks. Thanks everyone for the thoughtful replies.

[Captain Obvious]

One more idea. Kinda far fetched, but since we're throwing stuff out there...

There is supposed to be a spacer between the upper spring perch and the rubber insulator mount. On the front they use a bearing there so the front strut can spin when you turn the steering wheel. On the rear (since the rear doesn't have to spin) they use a hard plastic spacer instead.

I only bring this up because I don't see the spacer in your pics. Maybe it's stuck inside the rubber mount, or maybe someone lost it along the way?

Here's a pic of the upper insulator mounts and their respective bearings/spacers. Rear pair on top and front pair on bottom:

Good luck with the continued hunt for the noise.  

[Captain Obvious]

Nevermind... I think I see your plastic spacer stuck inside the rubber insulator mount:

[Zed Head]

17 hours ago, Randalla said:

Correct struts are ordered. I'll report back here on progress and results in a couple of weeks. Thanks everyone for the thoughtful replies.

Are you saying that he had the wrong ones installed?  You said that they were new in the first post and that it's an early model.  That would be short in short.  How can they be wrong?  Not really clear what's going on. 

[Randalla]

The struts were recently replaced by someone else to try to solve the problem, but from the pictures posted on Rock Auto showing both early and late strut cartridges, it appears that person used the later inserts. When I take the strut apart next time I'll be able to verify if he has the correct KYB part number. If not I'll swap them. If he does have the correct part number I'll have to keep searching for the problem.

[arcdef]

@Randalla did you get to the bottom of this?

[Randalla]

We've made incremental improvements, but it still doesn't seem quite right, though I'd say it's maybe 50% better. Turns out the strut inserts were the correct ones for his car after all, and after seeing both versions in the flesh I don't really see any way they could be assembled incorrectly, as dimensionally they are quite different. Any improvements made can be attributed to three things I think. I added a small amount of gear oil in the strut tube before inserting the KYB inserts to neutralize any harmonics that could have been created. I also replaced the spacer between the spring perch and insulator, though it was only a small amount compressed/deformed. Tires on his car were set at 35 lbs., so I deflated them temporarily to 25 lbs. as an experiment. I did climb in the hatch with my stethoscope to see if I could isolate where the noise was coming from when driving over the road reflectors. Unfortunately that did not yield any new information. This is a moving target but we do seem to be moving in the right direction.