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Triumph TR6 - Clack-clack-clack-clack-clack.....

Hi there! Background: I had (among other things) the suspension & drivetrain checked and where necessary rebuild last winter. I also installed new U-joints, spax telescopic conversion, new bushes etc. I also now have new (=rebuilt) rear hubs.

Now, then.... One day I start hearing a clack-clack-clack from the rear. I first heard it in the morning, and in the evening the same day it had got really worse (=louder). It is a clearly noticable clack-clack-clack, only during high revs and/or high speed it is difficult to hear. It increases with speed (not rpm), and appears whenever the drivtrain is under load, even a little is enough, but it seems to disappear when you ease off the pedal.

Took it to my mechanic (not a TR specialist, but it is considered a "lbc-shop"). We drove it, listened to it, lifted the car up and scratched our heads... We also noticed that LR wheel has a more pronounced lean in, which I hadn't noticed before, I really think I would have but I'm not 100%... Diff mounts look good, the rubber bushings seems fine.

My mechanic is now going to open up the diff, as he thinks its the only possibility. He also thinks that whatever is vrong with the diff would take care of the lean in.

Question: I suppose my mechanic is raight in assuming it's the diff (??), but how can whatever is vrong with diff affect the lean in?? And does the diff break down like this in a day??

TIA for any input!

SR
SignalRed

What you describe sounds more U-Joint related. If this mechanic seriously thinks that anything in the differential has anything to do with the negative camber (lean in) that you describe, stop him dead in his tracks and DO NOT let him remove and disassemble your differential. There is absolutely NOTHING related to the differential on the IRS TRs that has anything to do with the rear suspension alingment in either camber.

If it was differential mount related, this is typically more of a dull clunk under initial acceleration or gear changes, but if bad enough can also appear under acceleration in gear (especially lower gears).

As for the camber, it is altered by either use of shims under the springs or preferred, but much more work, by determining the current camber angle and verifying the bracket and notch orientation. This is then used to find the bracket and notch orientation combination that will provide proper camber. See either Buckeye Triumphs or Moss Motors caatalog for referenced tables. A much more recent option are a set of Richard Good's adjustable trailing arm brackets. One of our other board members has ordered a set and has promised a full report upon his return from vacation.

The rear toe settings are adjusted by shims placed between the trainling arm brackets and the frame rails to which they attach.

Here are the URLs of interest:

http://www.buckeyetriumphs.org/technical/Suspension/AdjRS/AdjRS.htm

http://www.buckeyetriumphs.org/technical/Suspension/RSGeometry/RSGeometry.htm

The second includes a somewhat rigorous analysis and derivation related to the issue. Trigonometry is such a wonderful tool.

http://www.goodparts.com/parts_susp_steer.html#trailingarmbrackets

The table does not show up as far as I know on Moss' website, but if you don't have one here is the catalog request URL:

https://mossmotors.com/CatalogRequest/RequestForm.aspx

SteveP

I got so hung up on the alignment part, that I failed to mention the other possibility. A sad, but typical case of "target lock" I'm afraid. That other possibility is the rear hub. If the bearings are going or the preload has been lost for whatever reason you can get the same sound. Bad bearings can make a clicking sound and not enough preload will increase negative camber. In general if it is the hub unit and it's gotten to the point that camber is affected, you should not be driving the car. If you can rock the wheel any amount, the hubs need a much closer look.

The rear hub bearings are not a job for the faint of heart or to be tried with inappropriate tools. More than one IRS TR rear hub has been ruined when tried on a conventional bearing press. Odds are that if your current isn't a TR specialist, he doesn't have the tools or know the tricks to rebuilding these hubs. If it is the hub unit, I would suggest that you get an exchange unit from someplace like TRF or one of the other places that have been recommended on this board in the past.
SteveP

Thanks Steve for your input!

U-joints: The four drive shaft joints are new, the prop shaft joints have not not been touched, at least not during my ownership.

Rear hubs: I bought reconditioned hub-units/assemblys from Rimmer Brothers (in the UK, in live in Finland myself) , so I think (hope??) there should not be a problem there, both were installed during this summer.

There is the possibility that I just did not notice negative camber on the LR wheel earlier, that it has just appeared during this summer or something. But it sure seems odd that we noticed it at the same time as this scary noice...

I am by no means an expert in these things, but I have been told by other people taht U-joint and diff noice can sound quite similar??

It is the connection (??) to this neg. camber thas puzzles me the most. And the that this sound/problem developed under one day during wich I even was not driving very much...

Anyways, thanks for your comments (the buckeye site is familiar to me, its a wealth of information!)

SR
SignalRed

Hi SR

I agree with Steve IRS diff will never cause a wheel problem. And I've never heard one clack in any car under load.

First check the shock setup for loose bolts broken etc. Don't like that stuff.

For camber look at the trailing arm studs inside on the back plate.

Next check the trailing arm frame mounts. Run a flat edge across with the car on ramps not on lifts.

Clack may be caused by half shaft running in an eliptical arc. The splines between yokes are slapping in and out?

No guarantee but thats what I would be looking for. You do need the weight on the back wheels either on ramp or simulated to create the camber problem.

One fellow did have a diff mount problem that let the drive shaft shift so much under torque it made a noise also something to check. Not a lot of room there and you should see some scuff maks. That would not cause camber though

Bill
Bill Brayford

SR - One other thing to check is whether the bolts on the diff to wheel shaft flanges are tight. Believe me when I say you will get all kinds of "new" noises when they are loose. It's not a "look" job - you need to get up in there with the wrenches. Since you did say the hubs were new, the bolting has to have been recent. Check 'em out. It's easier than being stranded.

BB
Brent B

This thread was discussed between 21/08/2004 and 25/08/2004

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