Chris :
This is a perennial topic of contention. As best I can tell, the facts are
:
1) The maker of the overdrive, Laycock, specified motor oil, and issued a
specific warning against using "hypoid" oil in the overdrive, as it would
"damage" the clutch. The overdrive of course shares oil with the gearbox.
2) Triumph originally followed Laycock's recommendation, and specified motor
oil for both OD and non-OD gearboxes for the TR2/3. This is in the original
TR2/3 workshop manual and driver's manual.
3) Apparently around 1960 (and definitely by the time the TR4 workshop
manual was printed), Triumph changed their recommendation to GL4 grade gear
oil. This was apparently in reaction to some gearbox failures (I forget
which part exactly) and in contradiction to Laycock's recommendation, which
never changed. All of the other car makers using the Laycock overdrives
(MG, Austin, Volvo, etc.) still recommended motor oil.
4) Conventional GL4 gear oil does contain a sulfur-based "extreme pressure"
additive that can, under certain conditions of high heat (and pressure ?),
break down to form sulfuric acid, which will attack the brass synchro rings,
thrust washers, etc. found in the TR gearbox. However, it's not clear that
these conditions exist anywhere except on the race track. Many people are
using GL4 with no problem. BTW it's apparently this additive that gives
gear oil it's distinctive smell.
5) Conventional GL5 contains even more of the sulfur-based EP additive than
GL4. However, since GL5 still meets the specifications for GL4, some oil
makers may be selling GL5 oil as GL4.
6) According to Redline, their synthetic GL4 gear oil (Redline MTL) does not
contain the sulfur additive, as their base oil meets the EP requirements for
GL4. However, there have been other problems reported from the race track
with using MTL (it apparently does not allow enough friction for the synchro
rings and the gear detents to work properly). Again, some people use it
with no problems.
7) Ken Gillanders at British Frame and Engine has been using Valvoline
Racing 20W50 oil in several OD transmissions, both on and off the race
track, for some 15 years now, and has seen no problems related to the oil.
The racing oil contains high levels of a zinc-based "anti-wear" additive
that also give it extreme pressure properties far better than the motor oil
of the 60s. His personal TR2 has been torn down several times to inspect
for wear, with none found.
My conclusion is to use the Valvoline Racing 20W50 motor oil in my OD
tranny.
Randall
59 TR3A daily driver
> -----Original Message-----
> From: Chris De Wet
>
> According to the DPO the gearbox should be filled with normal
> ( 20W30 )
> engine oil . Is this correct ?
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