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Posted (edited)

yes I know this is a very common issue but Ive tried almost everything now. my issue is a slight clunk/knock in the rear whenever the clutch pedal is not engaged/disengaged completely smooth, its more noticeable around corners shifting from 1st to 2nd, also does it when going straight and sometimes from reverse. this is a 3.9 r200 diff, bought used and never made any noise for the months I drove it after installing. heres what Ive done so far

 

-new mustache bar bushings

-new diff mount and steel cable straps in addition to the joke pathetic factory strap that sits above diff

-rebuilt half shafts

-new trans mount

-new wheel bearings

-fresh diff fluid 75w90

-checked all mount bolts making sure they are tight

-driveshaft is a used unit but never made noise for months as well, no play in ujoints

-new kyb struts all around and gland nuts are tight as can be

 

rear control arms are original with factory bushings but they look to be in decent condition still.. at my wits end with this car, Im seriously starting to hate the damn thing. steering wheel shakes as well at certain highway speeds but Im hoping its just the shop who balanced the tires did a shitty job, all new control arms/bushings in the front end.. grrr🤬

Edited by alex44

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I did a FAQ post on diff clunks that might help. Sounds like you've been over the most common causes.

On the tires, make sure they're dynamically balanced with weights on both sides of the rims (if needed). I've actually had the OWNER of a tire shop tell me that his tire balancer does a dynamic balance with weights only on the inside of the rim. He told me it was a dynamic balancing machine, and therefore only did dynamic balances, even if weights on one side. Dumbass.

Just on the off chance--I had a weird issue with what I thought was a balance issue on my Z, turned out to be a slip on wheel spacer from the auto parts store with a pilot hole that was .005" or something like that too small ID. It LOOKED like it was on flat against the hub but when I tightened the lugs it would warp and cause what felt like tire balance issues. Finally switched to lugcentric spacer from www.colemanracing.com and that solved it. dpracing.com carries good spacers too.

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Posted (edited)

Don't bother with straps. Just get the RT style diff mount
https://www.technoversions.com/DiffMountHome.html

There's also the chance your half shafts are contributing to the noise if there's play in them. 

 

Edit: Misread your post, I wasn't sure if this is what you meant by new diff mount.

Edited by Zetsaz

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Posted (edited)
48 minutes ago, alex44 said:

my issue is a slight clunk/knock in the rear whenever the clutch pedal is not engaged/disengaged completely smooth,

 

I can't figure out what the heck you mean.  Could you add some words?

 

p.s. "engaged" is clutch pedal up.  "disengaged" is clutch pedal down.  But you still need to add some descriptive phrases also.  When, exactly, do you hear the clunk/knock?

Edited by NewZed

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5 minutes ago, NewZed said:

 

I can't figure out what the heck you mean.  Could you add some words?

 

p.s. "engaged" is clutch pedal up.  "disengaged" is clutch pedal down.  But you still need to add some descriptive phrases also.  When, exactly, do you hear the clunk/knock?

lol..are you serious did you even read my post? "my issue is a slight clunk/knock in the rear whenever the clutch pedal is not engaged/disengaged completely smooth, its more noticeable around corners shifting from 1st to 2nd, also does it when going straight and sometimes from reverse. "

 

how is that not descriptive enough? I can re write it in french if that helps? basically its 1-2- 3 gear shifts and when Im on the throttle and remove my foot quickly, but mainly when shifting quick. dont know what else to say...

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Posted (edited)
30 minutes ago, alex44 said:

 whenever the clutch pedal is not engaged/disengaged completely smooth,

 

Sorry.  I have the disadvantage of too much good schooling, I guess.  Proper grammar would be "engaged/disengaged smoothly".  Not "completely smooth".  My over-trained brain was expecting different words.

 

Never mind.  Too early for word battles.  Good luck.

 

 

Edited by NewZed

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1 hour ago, NewZed said:

 

Sorry.  I have the disadvantage of too much good schooling, I guess.  Proper grammar would be "engaged/disengaged smoothly".  Not "completely smooth".  My over-trained brain was expecting different words.

 

Never mind.  Too early for word battles.  Good luck.

 

yep keep telling yourself that, whatever helps you sleep at night, old man. I didnt come here for grammar lessons, oh Im so ******* sorry you couldnt understand smoothly from completely smooth clutch pedal engagement/disengagement.. I now know the proper term, smoothly! ah how silly of me. must be my lack of schooling. please piss off from my thread and go shout at some clouds or something. & I remember your name from lurking on here a year ago, do you ever post anything useful? guess not.

 

thanks Jmortensen Ill look for that FAQ.

 

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At least I get the satisfaction of realizing that my intuition was right.  I saw the first post and thought that I might not enjoy a dialog with the poster.  But I took a chance, to see which way things would go.  Could easily have gone the other way, with acknowledgement, a simple clarification, and offering some ideas.  Oh well.  I miss those old days.

 

Good luck JMort.

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"Gland nuts are tight as can be" sounds a bit concerning. I do know some variants of the shocks required spacers that were not included with a definite feeling of bottoming out.

 

I second the RT style mount, just from a design standpoint it is better and with the snubber on the bottom you don't get any diff movement to contribute to potential clunks.

 

Can you get a clunk off of a launch? It sounds like you hit some of the most common areas, so short of something glaring it may be something minor like a loose control arm bolt (the big one on the front and back of the rear control arm like to come loose) or something more in detail like a loose stub axle nut.

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I'll add another endorsement for the RT-style mount.  I don't believe Ron had produced any in a while, but Technoversions still produces the unit IINM.  Check it at:  https://www.technoversions.com/DiffMountHome.html

 

WRT the rear end clunking, I had a very similar (and vexing) issue with my car.  Turned out to be the bushings in the rear LCAs.  I know you said that yours are stock and appear to be in good condition, but when I replaced mine with some new PU bushings, it solved the problem.

 

WRT the front end shake at speed, try swapping your front and rear wheels to check if there's any difference.  Like you say, it might just be a poor job of balancing the front wheels.  Look for a tire shop that can do "road force measurement" (IME most tire shops do not perform this analysis).  Many times your wheel can be "in balance", but can cause shimmy and shake due to other issues that the road force measurement can detect (e.g. flat spots, wheel out of round or out of true, etc.)

 

Lastly, go easy on the folk here if they ask for clarification or additional information.  99.9% of the folks on HybridZ have a wealth of knowledge and really do want to help fellow Z owners.  You'll find the forums here much more informative and helpful than the dozens of often-uninformed comments on social media, IMHO.

 

Good luck with it, and please be sure to post your results once you've resolved the issue so others can benefit from your efforts!  :-)

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@seattlejester KYB shocks were installed months before the clunk began, I know what you mean by the spacers and didnt need to use any as the struts sit fine in their housings. I should have mentioned, that before doing the mustache bar bushings, diff mount+straps, trans mounts, I had much much worse clunk then I have now. after all that work was completed I had no clunking or noise from the rear end for a few months of driving. now all of a sudden I have this new clunk but its slightly different sounding compared to the original clunk which was solved at the time by the work mentioned above. I dont really ever launch the car so dont know, but will try tomorrow. as for the gland nuts I guess I can pull the halfshaft and check the torque because I did replace that wheel bearing recently, lets say about 2 months ago?

 

@jhm

I really really hope its a bad bushing in the rear LCA! I just visually inspected them yesterday but that doesnt mean too much I guess, aside from just staring them down I will try and see if I can stick a flat bar in there and check if theres a lot of play. for the wheels I have swapped them back to front and still the same issue, shaky steering wheel at certain highway speeds, otherwise its quite a SMOOTH (lol..) ride. I wouldnt be surprised if the el cheapo tire shop I took them to did a bad job or missed a out of round wheel/flat spot on tire, they have a very basic and old tire balancer so wont be using them anymore. will look for a shop that does road force measurements and try again. I plan to update this whenever I figure out the issue.

 

and last but not least..

@NewZed

its quite funny you mention satisfying intuition. when I saw that you had replied to the thread for the first time I said to myself, I remember this guy oh boy this will be good... and lo and behold it was! but I do really appreciate the grammar lessons, seriously I do. seems I must have rubbed you the wrong way by saying I 'hated this car' or something, and thats too bad as I was really hoping we could be good old buddies..😭.. oh well

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Just to clarify I don't mean a hard launch, I mean taking off from a stop. Like do you feel it immediately when you let off the clutch or is it as you get moving or is it as the suspension squats?

 

I will second JHM my last clunk I had to deal with (other than VLSD axles) was from the RLCA bolts holding the inboard bushings. Found them several turns out after refreshing the suspension. Technoversion is where I and several of my friends picked up our RT style mount. Doesn't hurt that he's local.

 

Clarification is never a bad thing. Remember, no one gets paid on a forum to answer questions. Sometimes it is hard to imagine the problem when some aspect is unclear. Heck sometimes I know I don't want to read a post if it is really long and poorly formatted. 

 

I know it can suck, I still have a warning from a capitalization failure, but take it as a chance to try a bit more, maybe consider it payment for the free advice.

 

Speaking of...forum rule, make sure to capitalize.

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4 hours ago, seattlejester said:

Just to clarify I don't mean a hard launch, I mean taking off from a stop. Like do you feel it immediately when you let off the clutch or is it as you get moving or is it as the suspension squats?

 

I will second JHM my last clunk I had to deal with (other than VLSD axles) was from the RLCA bolts holding the inboard bushings. Found them several turns out after refreshing the suspension. Technoversion is where I and several of my friends picked up our RT style mount. Doesn't hurt that he's local.

 

Clarification is never a bad thing. Remember, no one gets paid on a forum to answer questions. Sometimes it is hard to imagine the problem when some aspect is unclear. Heck sometimes I know I don't want to read a post if it is really long and poorly formatted. 

 

I know it can suck, I still have a warning from a capitalization failure, but take it as a chance to try a bit more, maybe consider it payment for the free advice.

 

Speaking of...forum rule, make sure to capitalize.

Ah ok wasn't sure if you meant a hard launch or just starting in first gear, yes it does make the clunk when taking off from 1st gear but sometimes no clunk, depends how roughly I engage the clutch to get moving and when shifting from 1-2. Suspension is pretty stiff not sure if it squats that much. When flooring it and shifting hard I don't even notice the clunk as its pretty quiet, but still noticeable enough to drive me insane when cruising around slowly and in stop and go. It's most noticeable when in 1st gear and I take it to about 4000 rpm then abruptly take my foot off the gas pedal. Almost want to say that it sounds to be coming from the passenger side rear somewhere, which is the side I did the rear wheel bearing on. Also meant to say in last post will check the stub axle nut torque but wrote "gland nut" by accident. Impossible to say for sure I know but could this be an issue with the diff internals? I drained the fluid the other day and didn't notice any flakes in oil, just a tiny bit of metal dust on the magnetic drain bolt which I'm assuming is just normal wear and tear.. This might not matter but the l28 is turbocharged and probably making around 300hp at 15psi which I think is still low enough power for the stock drivetrain/halfshafts/driveshaft to handle?

 

Didn't know about the capitalization rule lol that's definitely a first I've ever heard of this on any forums, but ok no worries will do. I've just been writing everything on my phone as I'm out and about, so I type fast and using the caps button on my phones keyboard is a PITA but I will type from my computer when I'm home from now on to talk here.👌

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Posted (edited)

"Also meant to say in last post will check the stub axle nut torque but wrote "gland nut" by accident."

 

  • Torquing that nut beyond specs won't help unless the nut has actually loosened up. I torque mine to 180 ft lbs and quit. Be aware that the stock nut is staked down and turning the nut without removing the staked part with a Dremel grinder will destroy the threads on the axle. You can substitute a 280XZ nut which is self locking.
  • The splines in the companion flange (connects half shaft to the axle) can become worn creating some slop, but not a clunk. Lock the wheel and move the half shaft to see if the splines are worn. There is always a bit of play.
  • You should pull the differential and inspect for worn parts. 
  • Also check the three nuts (top of tower) for the insulators and the nut  that attaches the shock to the insulator.
  • All R180 and R200 differentials were a bit playful even when new and will clunk unless you engage the clutch smoothly. My junk yard R200 has clunked for the last 10 years.
  • Check that the shock has no vertical play which could indicate the wrong shock, missing spacer or loose gland nut.  Be careful around the threads that the gland nut screws into. If the threads get screwed up or the tube gets bent in the threaded area you will be looking for a new strut. Note that the spacer is unique to each manufacturers shock.
  • The stock front differential mount flexes. I replaced mine with a solid mount (MSA) 20 years ago.  No problems  with a SBC 350 or you can do the Taylor mount.

 

Example of cause of clunk in a R200 differential:

 

 

 

 

Edited by Miles

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45 minutes ago, Miles said:
  • The stock front differential mount flexes. I replaced mine with a solid mount (MSA) 20 years ago.  No problems  with a SBC 350 or you can do the Taylor mount.

You might want to check the crossmember for cracks. Plenty of ITS racers end up cracking the front crossmember that holds the diff mount with a weak 6 cyl.

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55 minutes ago, JMortensen said:

You might want to check the crossmember for cracks. Plenty of ITS racers end up cracking the front crossmember that holds the diff mount with a weak 6 cyl.

 

I do whenever the car is up on jack stands. Ok so far. I have seen that center mounting bolt pull out of the crossmember and cracked crossmenbers.

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Only forum I know of as well. Although I know other forums that have other interesting rule sets. Think of it as dressing up your post a bit if you need be. I'm sure this topic will be searched years down the line by future Z owners.

 

The noise at a sudden lift makes me think mount related. The stock setup even new has weaknesses especially with a sudden load transfer. I will say sometimes noises carry. I had a rattle that I swear was my tool bag only to find it was a loose plastic trim reverberating.

 

There are some intricacies involved with reassembling the rear wheel bearing, making sure the seal is seated and not interfering, the stub axle is fully in, the right spacer sleeve if you are mixing and matching. I also had to use an axle tool to get to the required 180ft lbs.

 

If it was the rear driver I might think about bottoming out an axle, but the rear passenger should be ok. 

 

Might be worth getting the car in the air and pulling and pushing to see if anything has play. It seems like it will be something glaringly obvious, or intricate and internal.

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Posted (edited)

Ok so some good news - doesn't seem to be the diff itself as it looks as if this sound is suspension (or possibly mount?) related. The clunk has got a bit more frequent and I've noticed it does it over bumps like when entering my steep driveway or dips in the road. Bad news is I still haven't pin pointed it to anything specific yet, just too hot and tired to get under my car again recently. I'm moving quite soon into a new apartment with an underground parking lot so I'm not sure how/if I will be able to work on my car at this point which really really sucks, but the owners of this suite where I'm at now want their downstairs back so it is what it is. Anyways, I checked the strut tower bolts and the strut nut itself, all were tight. If I can manage tomorrow I will get under the car (love doing this!) and look for anything loose on the LCA, Sway bar end links, etc. Sound appears to be coming from the rear passenger side. Passenger wheel bearing was done 6 months ago and it was done correctly, replaced the stock nut with a ZX nut, seals were fitted properly, used lots of grease. 

 

I don't think its mount related simply because the mustache bar bushings are new as well as the front diff mount, plus it has steel cables where the factory strap sits above and the steel cables wont allow the diff to move up more than 1".. But I could still be wrong on this

 

Appreciate all the tips so far thanks everyone.

Edited by alex44

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Heat is hard to beat, report back when you can. I know I've taken advantage of rent a lift type services to avoid getting scalded on the ground.

 

You only need a very small amount of play to make a fairly audible clunk. Loose sway bar link can make a real click to clunk depending on how loose it is.

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