Rob Y Posted August 1, 2021 Report Share Posted August 1, 2021 Hi Everyone, I have an annoying “clonking” at the rear underside of the car when going over sharp bumps. I thought it was the exhaust hitting the car as there is no central support bracket on my 73 CR car. However when I got under the car I couldn’t see where the exhaust was making contact, nor could I even simulate this by pushing the exhaust. There just didn’t seem to be any movement in the vertical direction. It would be really hard to fit the central bracket for several reasons, but I really don’t think this is the problem. Interestingly, with my brother in the car today the problem seemed less, so this is with a bit more weight in the car and I guess the suspension compressed a bit more. I have been unable to simulate the problem with the car stationary, bouncing the suspension with the car standing on its wheels doesn’t yield any clonking at all. Do you have any ideas what the problem might be and/or a way I can simulate the problem to check where it might be coming from please? Thanks in advance for any thoughts. Rob Quote Link to post Share on other sites
John Morrison Posted August 1, 2021 Report Share Posted August 1, 2021 Make sure the s/A bolts arereally tight, renowned for a clonk. John. Quote Link to post Share on other sites
Mike C Posted August 1, 2021 Report Share Posted August 1, 2021 Have a look for cracks in the shock absorber and diff mounting brackets. Quote Link to post Share on other sites
JohnC Posted August 2, 2021 Report Share Posted August 2, 2021 Perhaps a bump stop missing its rubber bit? Quote Link to post Share on other sites
Waldi Posted August 2, 2021 Report Share Posted August 2, 2021 And also check the bolts of the Armstrong dampers, they need to be torqued but can work loose. Waldi Quote Link to post Share on other sites
Rob Y Posted August 2, 2021 Author Report Share Posted August 2, 2021 Thanks, looks like I need to do some checks around the shock absorbers/Armstrong dampers. Diff mountings have been fixed and strengthened so shouldn’t be that. I don’t think it’s a drive related problem so shock absorber area sounds like a good area to look at. I’ll also check the bump stop, that’s easy to do while I’m looking. I will report back once I get a chance to have a look. Rob Quote Link to post Share on other sites
Rob Y Posted August 2, 2021 Author Report Share Posted August 2, 2021 Just thinking on this, if it was the shock absorbers wouldn’t I be able to feel/hear this by “bouncing” the back end when it’s stationary? Rob Quote Link to post Share on other sites
Tim D. Posted August 2, 2021 Report Share Posted August 2, 2021 Not always. Sometimes needs more of a jolt than you can do by hand. My tube shock bracket came loose at the end of a CLM trip. Real racket going over potholes. Nothing when bounced by hand. tim Quote Link to post Share on other sites
Rob Y Posted August 2, 2021 Author Report Share Posted August 2, 2021 Thanks Tim. The sound I get is not a single clonk, more of a rattle, but a clunky rattle if that makes sense. Nothing when driving or cornering on smooth or undulating roads, like you said it’s potholes or sharp bumps. Like I said in my original post it felt like the exhaust bashing against the body work or chassis, but I don’t think it’s that now. was it obvious that the bracket was loose, could you feel/see it easily enough when you checked with the wheels off the ground? Rob Quote Link to post Share on other sites
john.r.davies Posted August 2, 2021 Report Share Posted August 2, 2021 I''d say, get under the car with a pry bar, and lever it on all the suspension points. Unwanted movement will soon show up. John Quote Link to post Share on other sites
roughground Posted August 2, 2021 Report Share Posted August 2, 2021 I had the same problem chased it all over the rear but in the end it was slightly loose shock absorbers. Quote Link to post Share on other sites
jimcwestie Posted August 2, 2021 Report Share Posted August 2, 2021 I had to tighten up the rear telescopic damper bracket to fix a rattle/knock. Jim Quote Link to post Share on other sites
Z320 Posted August 2, 2021 Report Share Posted August 2, 2021 (edited) If you find all tight, like I always did every time I checked it: on my TR 4A the problem was the slack castled nut of the ingoing shaft of the diff. I thought it cannot become slack, because it is fixed with a pin or wire? But indeed it was because the massiv washer under the castled nut was punched by the time. Ciao, Marco Edited August 2, 2021 by Z320 Quote Link to post Share on other sites
Z320 Posted August 2, 2021 Report Share Posted August 2, 2021 (edited) double Edited August 2, 2021 by Z320 Quote Link to post Share on other sites
John McCormack Posted August 3, 2021 Report Share Posted August 3, 2021 I have telescopics on my TR6 but with my TR2s I have to tighten the lever arm shocks every 6 months or so. they start giving an occasional metallic clunk/rattle which get progressively worse. If you don't attend to it the mounting holes will wear and it becomes very difficult to get it tight. Quote Link to post Share on other sites
harrytr5 Posted August 3, 2021 Report Share Posted August 3, 2021 Armstrong lever arm shock absorbers The way I fix this problem is longer setscrews 2" x 7/16" UNF and fit nylocs on the other side. Works for me. Regards Harry Quote Link to post Share on other sites
Rob Y Posted August 3, 2021 Author Report Share Posted August 3, 2021 Thanks for all the feedback, seems pretty clear where I need to look. I’ll check it out tomorrow and hopefully find tightening the shock absorber mounting bolts fixes the problem. I will report back when done. Thanks. Rob Quote Link to post Share on other sites
stuart Posted August 3, 2021 Report Share Posted August 3, 2021 2 hours ago, harrytr5 said: Armstrong lever arm shock absorbers The way I fix this problem is longer setscrews 2" x 7/16" UNF and fit nylocs on the other side. Works for me. Regards Harry This ^^ Stuart. Quote Link to post Share on other sites
Peter Cobbold Posted August 3, 2021 Report Share Posted August 3, 2021 check the rubber joint between the lever arm and drop link, another known failure point. Quote Link to post Share on other sites
Motorsport Mickey Posted August 3, 2021 Report Share Posted August 3, 2021 I use longer cap heads, there isn't enough space for a socket to comfortably fit over the bolt head, it often seizes up between the edge of the bolt head and the leaver arm mount frame escutcheon. You torque it up and when you wiggle the socket out off the bolt head the bolt is still not up to torque. Mick Richards Quote Link to post Share on other sites
Tim D. Posted August 3, 2021 Report Share Posted August 3, 2021 3 hours ago, harrytr5 said: Armstrong lever arm shock absorbers The way I fix this problem is longer setscrews 2" x 7/16" UNF and fit nylocs on the other side. Works for me. Regards Harry Also did this for the mounting for my shock conversion after it came loose repeatedly. Been fine now for 5 years. Quote Link to post Share on other sites
Rob Y Posted August 4, 2021 Author Report Share Posted August 4, 2021 Thank you gentlemen! I was quite confident that this would fix the problem from all your comments. Interestingly though I couldn’t get any movement where the damper mounts were with the car on stands and swinging arm supported but the bolts did tighten up and the problem is fixed! The bolts on the offside needed tightening but the near side were tight. I love problems like this. Simple to fix, but transform the driving experience. I have had the car for 6 years and this is the first time I have needed to do this, so I will probably wait and see how it goes before fixing the problem with longer bolts and nyloc nuts. I can live with this frequency of adjustment. So happy with this, I can’t thank you enough. Cheers, Rob Quote Link to post Share on other sites
Drewmotty Posted August 4, 2021 Report Share Posted August 4, 2021 (edited) Nice tough cap head bolts with thick machined washers and high tensile nylocks are the answer. With proper tough fasteners you can get them properly tight without stripping anything. Edited September 2, 2021 by Drewmotty Quote Link to post Share on other sites
Alan B Posted September 2, 2021 Report Share Posted September 2, 2021 I have only just picked this topic up. For what its worth I had the same problem on my 6 and thought it was the exhaust. After having spent a long time checking and rechecking the clearances and moving brackets around to no effect I had a closer look at the chassis and found that the chassis cross member which holds the damper mountings had almost parted company with the main chassis frame and was banging up against the bottom of the boot. Some skilifull welding and strengthening and problem solved. Quote Link to post Share on other sites
DRD Posted September 2, 2021 Report Share Posted September 2, 2021 On 8/3/2021 at 10:01 AM, harrytr5 said: Armstrong lever arm shock absorbers The way I fix this problem is longer setscrews 2" x 7/16" UNF and fit nylocs on the other side. Works for me. Regards Harry Same here! Quote Link to post Share on other sites
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