[TR] TR6 rear shock mount break

[Tim Gaines]

It is a stormy where I am, so I'm inside with my laptop instead of under 
my TR6 working to get that rear shock mount cross member out. Somehow I 
must have deleted some of this thread, and I don't remember if I ever 
continued with my "fix" to the problem. I did carry it over to "The 
Triumph Experience" where I got some more recommendations, and though I 
was discouraged for a time, I am now very optimistic about my choices.

First, I got out the lever shocks that I had removed a couple of decades 
ago and opened them up and found the cause of their horrible 
performance. They were filled with grease! I found a Youtube video on 
the "Yakov's Beauties" site (so many great Triumph jobs there) that 
showed how to refurbish them. I did what he did and got a similar result 
where much more force was needed to move the levers. I really think they 
are going to work as is, but if not I'll get them done by one of the 
shops mentioned by others here.

Second, I did embark on an attempt to weld up and patch the cracks that 
had appeared on the left side of the cross member (gas tank out of 
course). I thought I could hold the pieces together with C-clamps and 
then spot weld them in a few places from underneath, up into the 
channel. The idea was to then add more to the welds in the channel and 
then weld patches to the outer surfaces of the channel that I would cut 
from 14 gauge sheet steel. I did get a couple of spot welds done, but 
the channel is narrow, the MIG nozzle is pretty wide, and it was very 
hard to see anything when the nozzle and my hand blocked the light. The 
killer was my discovery of another crack farther up near the 
differential that was in an even narrower spot. I called a local welder 
who was happy to come take a look at the possibility of doing a stick 
weld up there, but he said there was no way it could be done, and he 
thought the cracking would spread anyway. Total discouragement at that 
point because I just couldn't imagine incurring the expense of a 
frame-off job to install the RATCO Differential Tower replacement after 
post-Helene clearing and tree work had depleted our accounts.

A very helpful post on The Triumph Experience (from Ken D) let me know 
that the RATCO replacement could be done without removing the frame. 
"Read the instructions on the RATCO site," he said. I did, and the 
process sounded very doable, even for this 78 year old. I talked to Bob 
at RATCO, and got some good advice about carefully checking my frame for 
rust before proceeding. The cross member set up for lever shocks was not 
in stock, but it is likely to be shipped next week. Meanwhile I have 
been busy following the instructions. I'll briefly describe how things 
have gone for those who might be thinking of the same solution.

There was some initial frame prep required that would be very difficult 
to do without first making room by removing the hubs and half axles from 
the trailing arms and letting the arms hang lower. Each side has 6 nyloc 
nuts holding the hub to the cast aluminum trailing arm. All but one of 
mine came out nicely, but one nut was frozen to its stud, and that stud 
and nut unit re-tightened after several turns out. It was extremely 
tight and I feared stripping the aluminum threads in the arm by forcing 
it out. It took several hours (over a couple of days) of spraying Liquid 
Wrench, turning back in and then out, tapping the surrounding metal, 
applying heat with a heat gun (a torch might have been too much for the 
aluminum) to loosen the nut. It seemed interminable, but I did begin to 
feel that the nut was backing out a little farther on the stud, and it 
did finally give leaving the stud and arm threads intact. Whew. Another 
Yakov video showed how to simply pull out the hubs (no need to do 
anything with the diff). Mine were stuck, but I borrowed a hub puller 
with a slide hammer from Advance Auto (payed $175, got it refunded after 
pulling the hubs in 90 min).

I used my little air compression driven grinder with cutting wheel to 
slice the shock bump stops from the frame sides (to be re-welded later 
to a frame collar in the RATCO kit). It was a tedious job. I borrowed a 
friend's Makita electric angle grinder with a 4.5" diameter, .040" thick 
cutting wheel for the cuts to the old cross member. The cuts on the 
front side of the old cross member to separate it from the frame were 
about 6" long and took less than a minute each! The same cuts on the 
back side of the old cross were hindered by the bottom of the trunk area 
where the gas tank resides. Only about an inch of the cutting wheel 
could cut until the body of the angle grinder was blocked from moving 
farther in. This was incredibly discouraging, and I think it is the only 
flaw in the instructions provided by RATCO. Maybe there are low profile 
angle grinders that could work? I finally hit on the idea using my 
saws-all with a good long Diablo metal-cutting blade (I do have a few of 
my own tools at hand). It did a good job of cutting the rest of the way 
and took only a few minutes. I have used a grinding wheel to smooth out 
the metal left on the frame after some of the cuts, and that has gone 
well.

Yesterday I reinstalled the hubs using just 2 new nyloc nuts on each. 
The hardest part (not really bad) was sliding the new rubber boots (old 
ones worn) over the splines in the shafts before pushing them through 
the trailing arms (held up with a scrap piece of wood). This next is the 
best thing about the whole job. Tomorrow I plan to place a jack under 
the diff, remove the 4 nuts holding it to the mounts (2 in the old 
cross), and then lowering the jack to allow the diff to settle into a 
cradle of the 2 axles and the drive shaft. The only thing left holding 
the old cross in place is an easily accessed half inch weld on each 
frame rail. Should take about a minute to cut through those and then 
pull out the old cross. There will be more grinding to smooth the frame 
surface in preparation for the new cross member. That cross will be 
positioned by slowly jacking the diff back up into the 2 stationary 
forward mounts and into the mounts on the temporarily movable new cross. 
Ingenious! At that point my nearby pro welder has agreed to do the 
welding to the frame.

The current price tag on the RATCO kit is $375 plus shipping. The welder 
charges by the hour, but I don't think it should take too long. Maybe 
$200 or so there; certainly less than $800 total for the fix. That is 
more than I thought it would take originally, but this is much better 
than having an iffy patch job or a car that sits in the garage until . . 
. ?

Tim



------ Original Message ------
>From "Stan Foster" <stan at redtr6.com>
To "Tim Gaines" <mtgaines at presby.edu>; "Triumphs" 
<triumphs at autox.team.net>
Date 10/8/2025 5:37:30 PM
Subject RE: [TR] TR6 rear shock mount break

>I had those brackets and the stress caused the cross ember to be torn 
>off the frame. I fitted the cross member from RATCO and switched back 
>to lever arm schocks.
>
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>
>Stan
>
>
>
>From: Triumphs <triumphs-bounces at autox.team.net> On Behalf Of Tim 
>Gaines
>Sent: Wednesday, October 8, 2025 4:37 PM
>To: Triumphs <triumphs at autox.team.net>
>Subject: [TR] TR6 rear shock mount break
>
>
>
>I have been hearing a slapping sound either under or behind me in the 
>1974 TR6 when I encounter even slightly rough pavement, so today I 
>decided to sort it out. I thought I had found the problem quickly when 
>I saw that the spare tire securing hook bolt had come loose, but no 
>such luck. When I finally gave up on simple fixes and jacked up the 
>left rear end and removed the tire, I saw that the cross member had 
>cracked near where the after market shock mount adaptor bolts on. I did 
>a quick check with the Moss parts catalog and that cross member is not 
>available with them. So, I'm wondering if this shock mount replacement 
>for the old lever shock (I installed a couple of decades ago) was a bad 
>idea and put too much pressure on that frame member. It occurs to me 
>that there may be some folks out there who have gone through this and 
>can tell me just how a fix should be attempted.
>
>
>
>That crack shown in the photo seems to be only on the back side of the 
>cross member. I have learned some welding skills in the last few years, 
>and I have a mig welder, but I have never done anything under a car. I 
>really don't like the proximity of the gas tank either. I am thinking 
>that my local pro welder would be the guy to call on, but is this 
>really something that can be fixed that way?
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