MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

TR parts and Triumph parts, TR bits, Triumph Car Spares and accessories are available for TR2, TR3, TR3A, TR4, TR4A, TR5, TR6, TR7, TR8, Spitfire and Stag and other TR models are available from British car spares and parts company LBCarCo.

Triumph TR6 - Rear Clunk yet again

Hi All,

I am trying to track down a "clunk" in my rear end. I have read the archives and other usual sources, and am starting to think the noise may be coming from my U-joints, but was wondering if I could get some clarification.

I hear the noise intermittently while driving, and I can reproduce it while parked by bouncing the rear end. I took the right rear wheel off, then supported the hub on blocks so I can still bounce the car, and I have narrowed the clunk down to the forward part of the rear well. The clunk almost seems to be coming from inside the passenger compartment. I suppose there is a U-Joint from the drive shaft in there.

Could the clunk also be produced by the bushings on the trailing arms? If it is this, then the noise seems to be coming from the inner right bushing.

I guess my real question is, is this something to worry about, or just an annoyance? (I would rather work on getting the carbs tuned right now.) If the problem is with my differential mount, would not I hear the clunk coming from near the differential?

Thanks!
Ignatius

Iggy,
A U/j clunk occurs on changing speed, either accelerating from cruise, or lifting off. From your description though, a U/j is less likely than a shock absorber or, indeed, a worn bush. One to take seriously, especially the latter.

Disconnect the shocker and try bouncing again, to exclude that as a problem?
John
JohnD

JohnDee, Thanks for the idea of disconnecting the shock. Hopefully that is it. From the looks of the rear suspension, replacing those bushings looks like a pain.
Ig

Ignatius,
Another possibility is one I had to deal with, and while reading about if discovered its kind of a classic with the TR6. Your comments referring to the right side are pretty suspicious. If the clunk occurs when you accelerate, it may be the mounting bracket for the differential. The bracket on the frame was underbuilt for the torque it receives The standard break is the right front. which is right under the rear shelf behind the passenger seat.

You can get a pretty good look at it with the right wheel off. Follow the bolt up thru the bushing, and it mounts to a bracket that looks like is was formed by wrapping a flat piece of steel around a 2 by 4. Mine was cracked across the middle where the bolt is welded, and was very obvious once I found the bracket.

The only fix I found was unfortunately to remove the diff and have a welder mend the bracket. TRF sells a reinforcement plate (uses 4, by I could only work in 3), but my welder just made some of his own. Hope that's not it, but it's not too bad to fix if it is.

Mark
Mark H

I'd add to Mark's comment that a dull clunk from the seat-well region can also be caused by a fracturing of the pressed-steel bracket that bolts onto the nose of the differential. I have had this fracture (on the right side) so that the eye that is supported between the two rubber mounting washers comes completely adrift from the bit bolted to the diff nose. It's easily welded up once the diff is off the car.
If, as Mark says, it proves to be a loose pin, I have cut out the floor of the 'seat well' to get from above at the top of the pin where it pokes through the top of chassis cross member, which is impossible to weld well from below. Its a good idea to box the chassis frame around the pin too.
Peter Cobbold

Peter-I thought I was he only one who repaired the broken diff mount by cutting a small hole above the mounting pin. The frame is usually cracked around the pin, and should be welded. Also, I cut a 4"X4"X1/4" plate, drilled for the new pin, the plate is welded to the frame, then the pin welded to the plate. Some people may not want to cut a hole in the floor, but in my humble opinion, it is the only way to permanently repair the problem without removing the body. The small hole (approx. 4"X6") can be neatly cut with a die grinder and cut off wheel. Care must be taken not to cut the emergency brake cable that runs across the frame. The hole can be covered by welding in the piece removed or cutting a piece of sheet metal and riveting in place.
Berry

Hi Ignatius,

I have been reading the above thread with a lot of interest, as my TR6 also makes a thump & squeak while driving. I just finished bringing it to my mechanic and yep, it is exactly what everyone was telling us..cracked bracket. Just to prove, these guys do know what they are talking about.

Ted


T. Grant

Don K
Who his this Iggy character?
Dick C
Rick Crawford

Rick C,

As long as we figure my clunk noise out, you can call
me anything you want! ...even Johnie. Well, ok, maybe not that. I have got to draw the line somewhere. :)

Ignatius

Ps. I will out of town next week, so I will check the shock and differential mounts as everybody suggests 2 weeks from now. Hopefully it is the shock, bushings and welding sound like a pain. Thanks everybody for all the help!
Iggy

Well, I disconnected the shock arm from the suspension arm, bounced the car, and still heard the clunk when I bounced the car. ...ugh?

I do not usually hear the noise when I am changing speed unless I go over a bump, so I think John D is right that it probably is a U-Joint.

I felt around the differential mount and could not find an obvious crack/break. It actually looked pretty solid. I.e. after I brushed off all the dirt, it was mostly still painted black with only a couple small rust spots.

I will have somebody torque on the left tire as suggested on the VTR page, but is there away to isolate the suspension arm bushings as the source of the noise?

Somebody should write a book on TR noise diagnostics.

Thanks everybody!
Ignatius

Ignatius, (aka Iggy, Ig, Johnie...oops...sorry cross that one out:)
You just could not wait the 2 weeks eh? What did you do...wake up in the middle of the night in a cold sweat worying and get up and go do your testing???

Me thinks maybe you left out the word "not" in your second paragraph. John Ds point is that it probably is not a u/j. U/js are heard as one is on and off the gas peddle not from a road bump. You have disconnected the shock and noise is still there so it is not the shock. I presume you have confirmed nut tightness of all 4 mounting points of the dif. There are only 3 things left. The spring, the trailing arm attachment points, and the dif mounting points. The spring I think can be eliminated (unless it is broken, but this would be extremly obvious). I think you have a 2 person job here. A stethoscope would be handy here but if we owned one of them the car would most likely be going to a garage for everything. A nice Saturday afternoon drive up to Dons' home and I am sure he would be willing to do the bouncing while you do the listening...Don is a big enough guy..he would make a good bouncer:) Seems I recall someone saying a piece of wood makes a good listening device in one of your past "noise" threads.
Good luck Ignatius
Rick C

Rick Crawford

Rick C,

I missed my weekly psychotherapy session, so I figured I better go tinker with the car before I get ornery. The clunk is annoying more than worrisome.

The spring looked OK. Had some odd bright green paint on in when I cleaned it up though?

I need to replace the seals and gaskents in my differential. I will do this when I get back, and check these bolts then.

Ignatius
Ignatius

Ignatius
Leave the green paint on. It is factory paint to let the guy on the production line know that a green spring goes on the back of a TR6....ok trivia time...what is the colour of the paint dab on front springs of a TR6??
You will be able to have a much better look at the dif mount points with it out. If it does not have the "extra boxing" then consider having it put on when the dif is out otherwise it sounds like you will need to cut a hole in the back shelf of the car.
Yes Ignatius, Canada is big...it is that country north of you:) The interesting thing is that I actually live south of you...maybe 300 miles
P.S. sorry to hear you missed your appointment
Rick C
Rick Crawford

OK guys - You all know I have a TR3A, but for years, I had a clunk in the rear when I would hit a bump. Only when I hit a bump !!! I have the original lever shocks on the rear of my TR3A. I don't know if you have similar shocks on your TR6's. But I found that the bolts were loose holding the shocks to the frame.

Bolts are meant to be tight in "tension" - like for head bolts. But the 2 bolts for each of my shocks hold them "in shear". Bolts were not designed to hold things tight in shear. When I would go over a bump, the tire would go up, the lever on the shock would go up, and because the 2 bolts were not 110% tight, the shock body was rotating about 1'16" in the sloppy holes that were now becoming more and more oval. hat made the clunk !!!

Now I tighten my rear shock 110% every spring or when I hear the clunk again.

THE CLUNK IS NO LONGER THERE !

Ignatius - You should ask for a refund from your psychoanalyst if this solves your "CLUNK" !

Send me the refund.

Let us all know what you find.

Don Elliott, Original Owner, 1958 TR3A

P.S. - I'm going to the vintage Triumph races next week at Mid-Ohio - 1000 Triumphs will be there and 55 to 60 racers from USA plus 14 or 15 racers coming from England)
Don Elliott

Not only is that bolt in shear, it is in single bolt shear. A loose shock bolt will allow a clunk, it can lead to catastrpohic failure of the bolt, it can break or grind away at the mount ears on the shock. Having had to drill out a broken shock mount bolt (sharp clunk on bumps as opposed to on acceleration) on a TR6, my advice, don't let this happen to you! My solution is to run longer bolts then put nuts on the protruding threaded section to help keep the bolts from backing off.
SteveP

Ah come one Don E...we all get to share the refund. After all, we are the ones with the good SHOCK therapy. OK...no more groans. Don E, FYI..TR6s also are original with lever arm shocks but you have read past threads where some guys have done a conversion to tube type shocks. Don & Steve keep in mind that Ignatius disconnected the shock arm and still has his Clunk (6 posts up). But, this is still good info. I found on mine that the lower 2 nuts on the link arm at the trailing arm (to many arms here:)where loose. SteveP, maybe your 6 is different than mine. I have 2 bolts holding my Girlings to the frame. The mounting point is to a bracket/plate welded to the rear dif mounting arm. The plate is threaded. So it would appear that Coventry saw the problem in Mr. Es' 3A and corrected it at some point...obviously by 6. Steve are you saying these 2 bolts are designed to shear off? The torque spec. for these bolts is 65 Lbs Ft ( 9.0 Kgf m for u metric connoisseurs:)...this is pushing head bolt torque.
Rick C
Ha Don, have fun at Mid-Ohio, let us know your gas mileage for this trip.
Rick Crawford

Rick,

Never said that the bolts were designed to shear off, but excessive shear loads are a potential failure mode due to a loose bolt. The primary loading on the bolt is in what is known as single bolt shear. In double bolt shear, a member fits into a yoke with the pin going through the outer legs of the yoke and the piece being held in place. It is still shear and total loads are the same, but now the bending moments and shear loads are split, so the point loadings are not as high. It is across the shank between two members with the load being in shear as opposed to tension or compression. It also puts in a single large bending moment. If the bolt loosens, the damper can try and rotate along the bore of the mount and the axis of the bolt with suspension movement or sharp impact point loads can be applied directly in shear. The bolts cannot take much of that without failing. Plus you ruin the damper.

From a functional standpoint, the tensile loading on the bolt is a secondary load, the relatively high torque value specified is probably an attempt to make sure that the bolt does not back out. It works most of the time, but not always.

As far as the plate goes, same set up on all TR6, TR5, TR250, TR4A (both IRS and solid axle). The nut and bolt set up was used on TR2, TR3, TR3A, TR3B and TR4. I just run a longer bolt through the mount so that it sticks further out of the plate. I then run a nut onto this protruding section. This acts as a jam nut to lock the bolt in place so it cannot back out.
SteveP

Steve
not being an engineer...well simply I learned something today. I obviously took the words "....single bolt shear" to mean a single bolt "breaking"..now I have learned there is double bolt shear! I was thinking shear off not shear load. I know u have the same set up as me Steve....read my thinking of what I thought u meant. So now I understand your reason for the longer bolt and extra nut. Thanks Steve for the engineering lesson. The nut sounds like a good idea.
Cheers
Rick C
(simple shade tree mechanic with an EXPENSIVE hobby:)
Rick Crawford

Don E et al, I was also experiencing a clunk in the rear end area and did a look see this weekend I remembered tightening my driver side shock mount bolts this winter but found that my passenger side was fine. So upon exam I was quite relieved to find that they had backed off about a 1/2" on each bolt, so follow Don's advice and look the area over closely. I also found that both rear exhaust supports were also loose. Some of us may still need to do diff support work at some point but tightening bolts is easier than welding.
Thanks Don,
Keith
KBD Dixon

Rick - I hope the dab on the front spring is green and blue, 'cause that is what I was supplied with. This may sound trivial but - is there a top and bottom? SC
Stephen

Gentlemen - This has nothing to do with clunks .....but about 6 comments above, Rick C. asked me to report my gas mileage for my trip to the Triumph races at Mid-Ohio.

I drove 1927 miles for the trip. For 1775 miles, I calculate thet I got 30.6 miles per Imperial gallon (25.5 miles per US gallon). My TR3A has the 1991 cc displacement compared to most where the owner has increased the capacity to 2138 with the TR4 displacement. I bought the last set of 1991 cc pistons, rings and liners from Peter Hepworth in West Yorkshire in 1988 when I was restoring my TR. At least that's what he said. My engine now has been driven almost 65,000 miles with these parts. I get better mileage than my TR3A friends when I convoy with them because I have the lower engine displacement. I conveyed down to Ohio alone (if one can convoy alone) and convoyed back most of the way with Jim Wallace of Smith Falls and his son in their 2002 Taurus wagon.

Oh yes, you'll probably ask - so I'll let you know. "What speed were you travelling ?" I left the campground in Geneva on the Lake (Lake Erie) in Ohio north of Cleveland at 9 AM and was home at 5:30 PM. I drove 570 miles through Buffalo, East to Syracuse, then North to Watertown and took the 401 to Montreal. That works out to a rolling average of 67 mph. I don't baby my TR3A to get good gas mileage.

Other than add oil, I didn't even have to use a screwdriver or a wrench on the TR during the trip. But one morning, after a torrential rainstorm (my tent is dry) I had to spray belt dressing onto my fan belt - it was screaching like a cat that was dying.

And I was honoured (British and Canadian spelling) to drive Peggy Kastner (wife of Kas K.) for 3 laps of the track for the parade laps.

Don Elliott, Original Owner, 1958 TR3A
Don Elliott

Don
Excellent mileage. To think a 44 year old car can put to shame a modern car re gas mileage is interesting. Sounds like u had a blast!
Rick C
P.S. Stephen..you win the prize. No there is no top or bottom.
Rick Crawford

This thread was discussed between 31/05/2002 and 30/06/2002

Triumph TR6 index

This thread is from the archive. The Live Triumph TR6 BBS is active now.