What grade oil to use in gearbox

[Burdy]

Ive got Gu ute and its due for a gearbox oil change ive bought valvoline Dura gear 75w/85 synthetic blend GL-4 spec oil it specifies in my manual to use a 75w/90 GL-4 spec oil would it hurt to use what ive got or am i better off buying the correct grade oil

[MikeH]

If you tend to stay in the south of the country it'll be fine. It may be a concern with long distance heavy towing in very hot conditions.
You will get a little bit more gear rollover noise in neutral, but who cares patrol boxes sound like a cement mixer full of bricks anyway.

[Burdy]

ah righto ill see hows it goes,what's the best oil to run in them and what oil do u run in your gearbox

[nabstud]

Castrol VMX-80. Lots have replaced their gearbox oil with something else then noticed some grinding/crunching during gear changes. They then use Castrol VMX-80 and the crunches/noises go away.

[MikeH]

Redline MT90 in the box and the transfer. i have manual hubs though. If you have auto hubs put dexron in the transfer

[jemmos]

x2 on the vmx 80!! heaps better shifting

[howsie]

Vmx80 after a while hurt my cruisers gearbox I'd run an antifriction additive as well or Mobil agrifluid 424 which already has the additive.

[thehanko]

with towing heavier loads should a different oil be used?

Thanks
Ben

[howsie]

usually a good idea to use a good thick oil when towing heavy loads long distance / regularly. First number is viscosity when cold and second is when hot so you want the second number as high as possible.

That and a full synthetic oil will hold viscosity better than a mineral / semi-synthetic oil.