TR4/4A Loose Rear Shocks on my IRS

[KVH]

The rattling and banging can sure be annoying. This is an old subject, and we all know it's a problem on the IRS models. The shock holes get worn, or worse yet the threads in the rear bridge get stripped and the shocks are loose and go pounding with each road imperfection.

I guess keenserts can't help since the holes for the bolts go all the way through.

I tried putting longer bolts in and then putting locknuts on the protruding threads on the rear of the bridge, but even that didn't help.

Is there a magic fix? I'm reluctant to go with tube shock conversions unless they really are superior and affix to a sturdy frame member.

Thanks for any help.

 

[TR3driver]

I don't know that this will work every time, but so far it's doing well for me. I ground down some grade 8 setup washers https://www.mcmaster.com/?m=true#98025a031/=xpvfh9 so they would fit snugly into the restricted area under the nut, then used "Stover" conical lock nuts on top of them (see photo below).

(I actually got the nuts from MMC, but it appears they have discontinued the conical style. Probably these would work just as well https://www.mcmaster.com/?m=true#92501a430/=xpvqu2 )

I also ground down a socket just a bit, so it would fit all the way into the space, with a bit of persuasion; and torqued the nuts to roughly 40 ftlb.

https://dmpfasteners.com/shop/3-8-2...c-4963?zenid=96353447a8a813d5cdfd1c881c665b41

 

[KVH]

Yes, better than nylon. I should've thought of that.

I'll check how much thread and bite I have on those bolts and might even replace them with grade 8 bolts if that's a good idea. Those grade 8 washers are just to provide a seat for the nut, correct?

Thanks for the advice. Much appreciated.

 

[Geo Hahn]

...I also ground down a socket just a bit, so it would fit all the way into the space, with a bit of persuasion; and torqued the nuts to roughly 40 ftlb.

Not sure how solid axle mounts compare to what you're dealing with but I also use Stover nuts but with socket head cap screws to get around the limited socket clearance.

On a non-TR application that is troublesome (works loose) I am trying a set of Nord-Lok washers. I have never used them before and am curious if they are good or just novelty items.

 

[KVH]

Very interesting. I may just hunt down those Stover nuts and try it. If you're saying you use those cap screws in place of a standard bolt would that be harder to tighten as much as by using a socket wrench on a hex head?

 

[Geo Hahn]

On the solid axle lever shocks it is nigh impossible to get a socket over the mounting bolt head - usually I would just jam a screwdriver between the bolt head and shock body and tighten the nut with a box wrench or open end wrench. With an Allen wrench on my ratchet I can get those socket head screws much tighter.

Again, the shocks and access are probably quite different on an IRS so perhaps SHCS are no advantage.

 

[TR3driver]

On the solid axle lever shocks it is nigh impossible to get a socket over the mounting bolt head - usually I would just jam a screwdriver between the bolt head and shock body

Hmm, mine have the bolt running the other way, so the bolt head is behind the bracket and the nut is against the shock. That means one bolt on each side is trapped by the body (unless you cut an access hole in the body, which apparently some cars already had?) Anyway, my "custom" socket is only modified for the last 1/4" or so, with about .015" removed from each side at the tip (for .030" total reduction in diameter) and tapered back to the full diameter. I sometimes have to tap on the end of an extension to get them into place, but not very hard. I use an extra long, extra thin (aka "tappet") wrench to hold the nut head, working blind.

My apologies, KVH, I missed (and forgot) you have an IRS 4A. I've only owned solid axle cars with lever shocks (the Stags have tube shocks in the rear), so I don't know if you have the same issue with the socket not fitting between the nut (or bolt head) and shock body. But I still believe the hardened washer plus Stover nut and good torque is a likely solution for you.

The aluminum of the shock body is relatively soft, and my hypothesis is that it deforms slightly under the stress of the car bouncing around and lets the joint loosen enough to move around. The movement under load loosens it further, until eventually it is loose with no load at all. Using a heavy flat washer in there helps spread the load out, to lessen the deformation and hopefully keep the joint tight under all conditions. Torquing the bolts until they stretch slightly is important as well, for the same reason.

Certainly nothing wrong with substituting a SHCS, but you might want to bump the torque up a bit higher. Since they are higher tensile, they won't stretch as far with only 40 ftlb applied.

 

[Geo Hahn]

Hmm, mine have the bolt running the other way, so the bolt head is behind the bracket and the nut is against the shock. That means one bolt on each side is trapped by the body (unless you cut an access hole in the body, which apparently some cars already had?)...

You're right of course - I had to reverse the bolt/nut orientation to take advantage of the SHCS. The one exception is the forward bolt on the drivers side shock which is as you say 'trapped'. There is an access hole behind it which appears to be factory - but alas it does not line up with the bolt.