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[Eric F]

Hi,

I have just purchased a 1973 TR6 and I am now part of the wonderful world of
Triumph owner ship.  I have noticed that when I release the clutch I hear a loud clunk coming from the rear end.  I have put the car on jack stands and inspected all of the diff mounts.  They appear to be solid with only surface rust and road grime.  The bushings have a few cracks, but appear to be in ok shape.  There does not appear to be any play in the bearings from racking the wheels back and forth.  I put the car in 1st gear and turned the rear wheel again.  It seem liked there was a little play in the wheel (it would partially turn before the differential would engage).  Can any one tell me if this is normal, or if not what the problem might be.  Thanks for you help.  Eric

[Darrell]

Eric,
It is normal for the TR6 IRS rear drive to make some noise.  That being said a loud clunk upon taking up the drive can come many sources.  The most common is cracked diff mounts on the frame.  The tiny cracks can be very hard to see even if you have the diff removed. Close inspection is required. There is a gusset kit available to fix this problem by welding reinforcement pieces to the diff mounts with the diff removed.  Almost all TR6's with higher milage on them will require this.

Other causes include: Worn splines where the half axles join, bad u-joints, cracks or rust damage where the trailing arms attach to the frame, bad wheel bearings and even tiny cracks in other areas of the frame.

If the noise is not loud and just a click, both my TR250 and TR6 which have had all the rear suspensions rebuilt, still make noises from the rear like that. I just turn the radio up a little louder. 
Hope this helps,
Darrell   

[herald948]

One other fairly common source of such a clunk is the lever-arm shock. The hold-down bolts can loosen to the point where the shock will move upon startup/change of direction. Sometimes simply tightening the bolts is enough, but occasionally it might require a slightly longer bolt and an additional locking nut on the "back end" of the bolt.

[Darrell]

Andy is for sure "right on" here.  All suspension parts need to tight as per the factory manual torque wrench settings to minimise noises.  I have many times went back after a rebuild to find things mysteriously loose.  Which reminds me of a true statement meant for British Car Rear Bumper Stickers:  "The parts falling off this car are of the finest British Manufacturer."
Cheers,
Darrell

[Eric F]

Darrell thanks for the informative response.  I do have the car in off the ground and I spun the rear wheel with the car in 1st gear.  It does seem to clunk a little once every revolution.  Is this the sign of warn u-joints on these cars or something else, or is it normal?  As for the differential mounts, do they typically crack on the stud, support brace or cross member.  I shined a flash light on the mounts and pulled the rear wheels to look at them and I cannot see any cracks on the outside?Also, thanks Andy for the tip on the shocks, I will check that out.

Eric

[charley fitch]

One more potential source of a CLUNK is if you have wire wheels.  Worn splines and wheels will do this.  I'm guessing that you do not have wire wheels.  But you will only hear it if the weight of the car is on the wheels when they try to change direction, eg. reverse to forward.  If you have this problem a new set of wheels and or splined hubs is in order.
Charley Fitch 

[Darrell]

Eric,
Typically the diff mount that cracks is on the trust side (right) on the part of the bracket that looks like a tent, that is where my Six was cracked. I could feel it better than seeing it. The same cracks were on my 250, trust side and the stud had previously been shoved up the crossmember and welded before I got the car. A broken diff mount will make noise whenever you stess the diff by downshifting & decelerating, etc too.

It's very hard to fault diagnose these problems but taking a guess at want you describe as a clunk every revolution while jacked, it may be bad u-joints or a bad hub bearing.  The u-joints can normally be greased and you can normally tell if you have a real bad one by checking for play. They usually will make a constant clicking noise that increses with speed or if they are real bad they will screech. Hubs are harder to tell if they are good or bad but will usually make a constamt roaring sound if bad.  Also I am not so sure you can really tell much with the car jacked for there really is a whole different type of load put on everything once it is on the ground.

We didn't sat anything about he diff itself.  I suppose the ring and pinnion could be worn too.  How many miles do you have on your Six?

Unfortunatly most guys I know follow the practise of "Fault Diagnoses by Part Substitution". Start with the easy stuff. Yikes   What do you other guys say?

Good Luck,  I will be at TRA for the rest of the week, I will check back then.
Darrell   

[Eric F]

Thanks again to everyone for the informative answers.  I will try the easy stuff first grease u joints, new shocks and springs (which it really needs)and new differential bushings.  Hopefully that will take care of the clunk.  If not, it will be time to open the check book. 

Eric

[tr6canuck]

I have the same clunking noise when I release the clutch in 1st gear.  I can also hear whistling at low speed.  I can't hear it on the highway (road noise).  I'm assuming it's the u-joints.  How hard is it to swap out the u-joints?  Yep, it was my u-joints!!  Had all 6 replaced.
Damian
Windsor,ON
'75 TR6 102,000 miles