[Mgs] Fwd: Re: 90w in Transmission?

[Paul Hunt]

Exactly so, this is why the V8 uses *gear* oil in the gearbox and OD and
*differential* oil in the rear axle, even though they are much the same
viscosity.  However the terms 'hypoy' and 'hypoid' and used in different
places in the V8 Workshop Manual Supplement according to manufacturer, Castrol
using 'hypoy' for both and Duckhams using 'hypoid' for both, the difference is
in suffixes and hence specifications of the oils.  Modern Castrol oils, here
at least, are much clearer in that the descriptions state 'gear' or
'differential' as appropriate.

The Leyland 4-cylinder Workshop Manual specifies engine oil for the gearbox
and OD.  The extra protection of gear oil isn't required like it is for the
much higher torque V8, but it won't do any harm and it doesn't result in a
stiff change, I've used my V8 on a daily basis parked outside in below
freezing temps and not had a problem.

PaulH.
  ----- Original Message -----


  The CHEMISTRY of all of this is such that a 90W oil is
  usually a differential lubricant.  The additives used
  in a differential oil will react with any non-steel
  components and cause failures. Any heavy trucker will
  confirm this if you need extra support. a 20W50 engine
  oil is the best for a MG transmission.  If you can
  find a 90W "gear only" oil that should work as well