What Oil In The Gearbox

[WelshBoy]

Hi All
Just about to refill my (manual gearbox) with oil the transfer case and gearbox side manual says to use the same oil thats in the engine 15/40 engine oil any advice??

[isuzurob]

Can run 75w/90 but can be hard to select gears when cold, 5w/30, 15w/40, anything really I've tried alsorts even 80w/90 works if that's all you have

[WelshBoy]

isuzurob wrote:Can run 75w/90 but can be hard to select gears when cold, 5w/30, 15w/40, anything really I've tried alsorts even 80w/90 works if that's all you have

Thanks will give the engine oil a try will be cheaper to use the same oil in the trans and motor.

[geeves]

Not quite unfortunately. Modern engine oils have friction modifiers which are great in the engine but dont play nice with syncro rings. It wont damage them if its already in there but when cold hard gear shifts are likely. If its in there and working well dont worry. The 3 options for the gearbox are
A: The cheapest oil of the same viscosity as the engine that you can find. Today that is still better oil than was available when the gearbox was designed.
B: 5 speed gear oil. There are a few brands on the market. Dont worry about the viscosity as gear oil is measured differently
C: Dexron 3 ATF However it likes to find ways out of the box
All the above work. One thing to avoid at all costs is diff oil. Diff oil additives eat brass synchro rings and break down at high temperatures into nasty things

[WelshBoy]

geeves wrote:Not quite unfortunately. Modern engine oils have friction modifiers which are great in the engine but dont play nice with syncro rings. It wont damage them if its already in there but when cold hard gear shifts are likely. If its in there and working well dont worry. The 3 options for the gearbox are
A: The cheapest oil of the same viscosity as the engine that you can find. Today that is still better oil than was available when the gearbox was designed.
B: 5 speed gear oil. There are a few brands on the market. Dont worry about the viscosity as gear oil is measured differently
C: Dexron 3 ATF However it likes to find ways out of the box
All the above work. One thing to avoid at all costs is diff oil. Diff oil additives eat brass synchro rings and break down at high temperatures into nasty things

Thanks have tried the engine oil nylon 15/40 will see how I get on

[Idontwantausername]

I own a 5 speed bighorn and would recommend 80w-90 gear oil
as Geeves points out gear oil is designed for gearbox's
I tried engine oil in mine and it made getting into 2nd when cold a grawnchy businesses.

[geeves]

Whatever you do never put oil with hypoid additives in the gearbox

[Kurjaga]

Hello! I have a 2011 Dmax 2.5diesel. I want to know what oil is poured into my manual gearbox? I have trouble switching between 1st and 2nd speeds, but it's only now that it's cold weather. Older models can use the same engine oil that the engine pours, or can it do the same? However, has a technical specification ever been written?
What can you suggest?

[geeves]

Handbook says same oil as engine but this does not take into account modern engine oil additives. These are the cause of your problem. You can use the cheapest engine oil you can find but the recommendations from mechanics here is to use a 5 speed gearbox oil like Castrol VMX or similar. Dexron ATF can also be used

[handymanny01]

I put something along the lines of 75/90 gearbox oil in mine, before I knew it was supposed to be engine oil.... years on,, it's still fine,, defo hard to shift when cold,,,, but my gut feeling is that the true GEARBOX oil, prob provides more protection to the bearings and gears, Especially on a modified engine ... so it's staying in there! If I was standard (un-modified) engine,,, I'd prob put the factory specified engine oil in...