Hi Peter:
I will route about in my notes and see if I can come up with the exact
details. In short however, it seems that the early TR6 transmissions uses a
set of caged roller bearings rolling within a hard shell. The shells were
inserted into the ends of the big gear on the layshaft (damned name escapes
me at this moment). For some reason (cost no doubt) the later ('71+) models
had the rollers inserted directly in the gear body. The problem was that the
gear metal was not hard enough to take the pressure and it wore rapidly.
This eventually resulted in the gear coming into direct contact with the
shaft. Soon after the rollers would disintegrate and that terrible growling
noise from the transmission indicating a still-moving contact began. It is
amazing how long these transmissions could run with this condition. After a
wihile the reduced contact surface due to the misalignement of the gear
faces would begin to break off the teeth of the layshaft gear. That's when
you are really stuck. My transmission completely self-distructed and I had
to find a new layshaft gear and rebuild the whole unit from scratch. I
determined to avoid this headache happening again.
Anyway, I had the machinists centre my slightly worn layshaft gear on the
lathe and bore in the roller races to a depth of two complete cages. Then I
inserted 2 shelled caged roller bearings on each end of the gear. This is
where my memory fails me, since I don't remember whether I used the shelled
rollers from the older transmission type , or a unit chosen from and SKF or
Timken catalogue. I did have a new shaft made up with very much better steel
and much deeper case-hardening. The shaft is just a straight shaft with a
small keyway cut at one end for the keeper. I recall that all the sizes in
the unit were quite simple to match. The idea is no that the rollers are
running on four tough shells, not 2 soft metal surfaces.
I would imagine that the change in bearing layout occurred at the same time
that the layshaft gear changed the number of teeth. I remember that there
are at least two models out there, that look very similar, but are not
interchangeable. Be careful if you are purchasing an old unit for upgrade,
to get the right thing. I have an extra that does not fit. Good luck in your
efforts.
Mark Hooper
-----Original Message-----
From: Peter Zaborski <peterz@merak.com>
To: 'Mark Hooper' <mhooper@pixelsystems.com>
Date: November 19, 1998 5:48 PM
Subject: RE: TR6 transmission oil
>>I have already bored out my layshaft for extra roller bearings
>>and used an industrial shaft not the piece of shiny solder the
>>car was originally fitted with. Only time will tell...
>
>Mark, I would be interested in the details of what you did here. Although
>not presently in need of any gearbox work, I am starting to hear (or rather
>notice) the telltale noise of the layshaft bearing -- car in neutral,
>noticeable noise from gearbox, press in clutch pedal, noise diminishes. So
>anything I can do to strengthen this known weak point would be great to
know
>in advance.
>
>BTW, my gearbox is a J-type and I use 80/90w GL4 spec oil. No trouble
>shifting or engaging O/D. Plus it's easier to discern when the gearbox
leaks
>-- that smell of sulfur is a dead give away.
>
>Thanks in advance,
>Peter
>
>--- Peter Zaborski CF58310UO ---
>
>
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