[TR] TR6 Plastic transmission Tunnel Fit

[John Macartney]

I do hope my verbosity doesn't auto-trash this reply from the server but I'm
able to tell you why these replacement tranny covers don't fit as expected.
>From what I have learned this far, it's a universal problem and I've found
the answer in a sheaf of papers written by my Dad back in the late 50's. For
those who are not aware, Dad was Quality Control Manager and Chief Inspector
at Standard-Triumph until the Leyland take-over.

 

The problem first raised its head with the start of Herald production. What
few people know is that key parts of Herald assembly were made by different
suppliers namely the scuttle (firewall) bonnet, floor and rear deck. As a
result and because the bodies were built up 'visually' and not in proper
body jigs, the conformity of panel gaps and door shut lines were achieved by
loosely assembling the entire structure and then using a variety of timber
levers and rubber mallets to achieve overall alignment in which the "it
looks about right" was the prime decider. This was by no means an exact
science and in the early years of the Herald's production life (certainly
the first two years) resulted in horrendous warranty costs through water
leakage. Gradually, they managed to get the issues sorted but with the
arrival of the TR4/4A/5/250/6 the bodies were assembled in much the same
way. That's why we never took visitors into the body assembly area as the
somewhat brutal way that things were put together was not felt desirable for
visitors to see!

 

The issue of the transmission tunnel was a major headache. The factory fit
version was made of a semi-liquid form of chewed cardboard put over a
perforated zinc former and bonded with fish glue which was then baked to
harden the assembly off. Initially, holes were drilled in this cover for
securing bolts to be fitted but more often than not the holes failed to line
up precisely with the chassis securing lugs. This was overcome (eventually)
by briefly fitting inked spikes into the chassis lugs, resting the tunnel
assembly on them and then hitting the appropriate point with a piece of one
inch die tube to achieve the approximate hole punch location. The tunnel was
then removed, inverted and the ink marks on the underside and scuttle mating
surfaces showed where the holes needed to be punched. Having now determined
the more or less precise position of the holes along the front and side
edges, the tunnel was then put into a separate jig to mark off how much of
the tail end needed to be removed with a circular saw.

Because of the 'variability' of where these holes eventually appeared means
that no two cars were exactly the same in all critical dimensions and this
is what the parts aftermarket has entirely overlooked. Those who now make
these tunnels have assumed (incorrectly) that the size and positioning of
the required holes was identical in every case and that's why they're such a
s*d to fit and why they're nearly always too short. Simply, someone has
obtained an old cover, assumed its dimension was/is a one-size-fits-all and
made accordingly. The originals were always made longer than necessary so
there was a tailend to remove and that amount of removable section depends
entirely on each individual car.

 

How do you overcome it? You can't - unless you're really lucky. A strip of
soft aluminium to bridge the back end is probably the only option open to
anyone. With regard to where you locate heat mat, I feel the underside is
probably better because if you plan to fit new carpets, these too will
probably come to fit an 'exact' dimension rather than a sloppy one which was
how the carpets were made in the past.

 

Hope this helps

 

Jonmac

 

 



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