May have found my "Clonk" - please confirm...

[Deschodt]

I've had that "clonk" in the rear (driver rear mostly but could be because that is closer to me) that happens when the car starts moving from a standstill - forward or reverse... Only happens during that initial movement, not in turns, not at speed, or I cannot hear it anyway... Also seems to happen on bumps but not as frequently...

I can now reproduce it by standing on the door sill and jumping up and down (does that even make sense for a CV issue?).. I took the wheel off and my first thought was the handbrake mechanism since my car also won't release the HB entirely when reversing (have to more fwd first)... But as I grabbed the hub by the studs and rotated it violently front/backfront/back (simulating a take off in 1st gear or reverse) , I could not feel the clonk in the hub, but could hear it down the shaft...Seems it's the inner CV joint that meets the transmission... I can feel something a bit of play there when it tart rotating from a standstill, but only when "kicking" the wheel in motion, once it's turning, nothing... I've read a bunch of CV joint threads since, seems like it definitely could be it, but nowhere as bad as described by others.... Still, @ 185000 miles, likely, right ?



I'm just checking with you guys because for all I know that is the way a normal driveshaft sounds and that little bit of play that can clonk may be be normal.. Can you just confirm it's not supposed to have that play there at all ? The other wheel (passenger rear) does it too, but a lot softer, 1/2 the clonk... So I'm pretty sure it's CV... Please advise, at this point, not sure what else to try to be 100% sure...

Last Q: I've tallied the price of parts and my expertise, and I wonder if I'm not better off buying whole rear axles since I'm gonna farm this out...

Thanks !!

PS: unrelated but the grease nipples for the polybronze bushings are supposed to be pointing at 9 O'clock so you can reach them to be greased. One of them is now pointing to 6PM and I can't put the grease gun on it anymore.. Uh oh, does this suggest it's binding and it moved there by itself ? (problem is 2 shops played with my ride height and they might have moved it when disassembling that side)

[JerryL]

My guess is CV Joint, not sure about the poly bronze issue, how ling have they been in, the OD should be locked from rotation for the center to allow rotation and therefore the lube deal work. I think it is press fit.

Regards

[Deschodt]

After reading Randy's thread, I think so too.. Could anyone confirm that there should be no play at all inside the inner CV when rotating a wheel "hard" from a standstill ? (serves as a bump too) ;-)

[RoninLB]

if you take one axle and rotate it forward and rearward there will be some play..

around 1/4".

and make sure your rear shock top nuts didn't loosen.

[Deschodt]

Well well...

$1097.80 later and I'm still clonking ! I'm not complaining mind you, my 911 has 185K miles and never had CV joints done in my ownership (over 100K and 13 years)... stuff that was done needed to be done, but...

The inner CV joints had too much play, both were replaced... $240 right there in parts, plus another $150 for a "kit" of nuts and bolts and 4 new boots... The outer ones were disassembled, repacked, and swapped around so that they wear the other way. All boots are new, the rear left axle nut was found to be loose and was retightened. So were the upper shock mounts but they were not loose... Nothing else was found ! The wheel bearings are still top notch (do those EVER wear out?), the handbrake drum was inspected and no problem there... My rotated elephant PB bushing was not a problem after all, someone else did that (other shop) - I'll have to rotate it back in place when it needs grease, next year ;-)

5+ hours of labor later doing the above and diagnosing, the thing still has a little clonk when it starts moving or climbs uneven driveways. I hate it, but now I know for sure nothing in the back of my car is in danger of falling off or leaving me stranded. It's something stupid, like a seat bracket maybe (just an example, pretty sure it's further back), but I can't put my finger on it yet !


Still open for other options... I'm gonna got poke around some more !

[equality72521]

Have you verified that your shocks, engine mounts, and trans mounts are all tight and in good shape?

[sbrown.nw]

I had a noise like you describe and it was a worn hub and the wheel bearing would build up tension and then slip (rotate) which would result in a "clonk" noise.

Scott

[Deschodt]

well the wheel bearings were inspected... I did engine and tranny mounts 2 years ago tops, and they are tight - well engine are for sure, haven't rechecked tranny ! I think it's something stupider... They noted that the left rear shock shaft is showing signs of wear, "replacement might be needed soon". The things are bilstein Hds from 1.5 year ago, WTF ? But that is what I'm leaning towards now... I can reproduce a clonk (hopefully "the" clonk) by standing on the door sill, rocking the car up and down with my 200 lbs fat ass. Unfortunately (or thankfully in this case) , my wife is much lighter and it does not do it for her...

I need to enlist the help of a fat neighbor and go listen while he jumps on my door sill !!

[jpnovak]

sway bar brackets/mounts?
sway bar drop links?
trailing arm bushings?

did you pull the shock out and manually inspect it for looseness or play?

If you can reproduce the clunk you should stepwise remove parts until the clunk stops. Start by disconnecting the sway bar and then rear shocks. Start with the simple things that do not disturb rear alignment.

[regency]

I too, had a weird "clonk" issue. I checked & double checked everything and still had it. Then, when Tom Amon ( Mobile Works West ) was jacking up the car to install the new engine, he said, "look at this" and shifted my rear wheel back and forth a bit. "thats not right"
"might be a wheel bearing". I advised him that I had new ones installed just last year. We pulled off the wheels to find that both wheel crown nuts weren't torqued down. Tom pulled the pins and actually got a few turns, then touque them tight. Needless to say, I won't be using the guy who installed the wheel bearings anymore.

[Deschodt]

Originally Posted by jpnovak

sway bar brackets/mounts?
sway bar drop links?
trailing arm bushings?

No, no and nope, all checked...

>did you pull the shock out and manually inspect it for looseness or play?

That I did not do, did not think I had a reason to on a 1.5y old shock, but like I said, now it is suspicious too (wear? after 1.5y?).. Honestly though I had no idea I could remove the shock and inspect it without undoing the alignment/corner balance... I'm gonna look that up now that you mention it ! The search is my friend ! ;-) Thanks !

[Tom '74 911]

When you did your suspension recently, did you put monoballs in the trailing arm mounts?

I have a similar noise in my car - it's just as you describe. I am posting as much to subscribe as to offer suggestions!

Tom

[Pazuzu]

I didn't get a sense if you told us...

You still get the clonk when driving, but do you still get it when grabbing the hub and turning it back and forth by hand?

What about (dreadful thought...) differential issues? I haven't really read anything about them going bad on here, so I don't know the standard diagnostic tests.

[Staylo]

So I went through a similar ordeal last year after a suspension rebuild. I even replaced an axle as you did.

My issue turned out to be the torsion bar cover plate.

It was the last thing I checked because I still had the clunk after a pro re-indexed and CB'd the car. I caught it because I too needed to rotate the PB zerk and had to take the cover off to do so. Upon putting it back together the noise was gone.
You may need to shim it with washers. I believe the Elephant PB's come with some just in case.
HTH!

[73rustbucket]

Disconnect rear shocks. Either it will stop clunking (in which case check shocks and mounts) or it will still clunk but much easier because disconnecting the shock will allow easier movement. This will make it easy to find.

[Deschodt]

Originally Posted by Staylo

So I went through a simialr ordeal last year after a suspension rebuild. I even replaced an axle as you did.

My issue turned out to be the torsion bar cover plate.

It was the last thing I checked because I still had the clunk after a pro re-indexed and CB'd the car. I caught it because I too needed to rotate the PB zerk and had to take the cover off to do so. Upon putting it back together the noise was gone.
You may need to shim it with washers. I believe the Elephant PB's come with some just in case.
HTH!

This is a good one... I've wondered about those shims, and I ned to rotate the PB zerk fitting (I like grease nipple better!) - will definitely try ! Once of the 4 mounts was cracking at the base and was welded back, so it's high on the suspects list...

Between that and the shock (and F1), you guys have filled my week end, thanks !

[mike_dunn]

I'm interested, I have the same clunk (or clonk) when engaging the clutch from a stand still or very low speeds. It's usually there but sometimes won't happen if revs are matched perfectly. So maybe I might be of help.

I've original CV's repacked and didn't look worn out, shocks are original, and new LR wheel bearing (need to find time for RR). I do know for a fact that the box is thrashed: the 2-1 shift is impossible without fully stopping, 1-2 will sometimes grind even after a long pause, and 2-3 has begun to make a light crunch. I also get a fast-spinning grinding coming from the the box on acceleration or deceleration (none if throttle is feathered). I've read the grinding is R&P related, but I can't say for sure as I'm a nitwit about these things. I do know the tranny is next on the project$ list.

[Deschodt]

Originally Posted by 73rustbucket

Disconnect rear shocks. Either it will stop clunking (in which case check shocks and mounts) or it will still clunk but much easier because disconnecting the shock will allow easier movement. This will make it easy to find.

Sorry if I'm thick here, but I cannot for the life of me find my copy of 101 projects - do I just undo the top nut and pull it from the bottom with the car on a lift ? Is it this simple ? The search after all was not my friend for removing/reinstalling rear shocks !

[73rustbucket]

Originally Posted by Deschodt

Sorry if I'm thick here, but I cannot for the life of me find my copy of 101 projects - do I just undo the top nut and pull it from the bottom with the car on a lift ? Is it this simple ? The search after all was not my friend for removing/reinstalling rear shocks !

No need to even jack it up. Unscrew the lower bolt only and make sure the shock is not hitting the trailing arm. Wire to header if needed.

[Bill Douglas]

My SC makes a loud clonk from that area as well. In fact it's done it for the last five years (the basta**) and I think it's the torque tube/bar thingie on the left hand side. Probably a worn out bush or something.