Same or different gear oil for manual box and transfer case ?

[sunrk]

That perennial question

I currently run Caltex VMX-M in both the 5-spd manual box (with Nulon G-70) and part-time transfer case (with no additive) of my 80. Looking to try something else.

I've had recommendations to firstly not use the same oil in both and secondly to go with Redline MT-90 for the gearbox and Redline Heavy Shockproof for the transfer case. They're readily available here in Australia for around A$100 or so each for a gallon (just under 4 litres).

I was considering going with Mobilfluid 424 in both the gearbox and transfer case but heaps of people are saying that's a bad move and while 424 will probably be great in the box it won't suit the transfer case due to high load and consequent heat that the smaller quantity of oil needs to accept.

I've probably done about 30000 km on the current fill of oils in both the box and transfer so an appropriate time to change them out.

 

[bigredmachine]

cant really specify on a specific fluid that your looking at but at work with the manual 4wd trucks we use the same gear oil in the trans, t-case and axels. I use the same gear oil in the axels and t-case on the 80

 

[maxamillion2345]

Theres some truth to the mt90 GL4 yellow metal syncro sulphur argument so thats a good option but if a gl5 shifts nicely then meh run a gl5 in both.
I’d run a gl5 in the tcase either way and while the redline shockproof is nice stuff idk if its worth the price. Theres 400,000+ mile 80 series that ran with 75-90 gl5 dino oil there whole lives, guaranteed. MT90 may shift smoother for you but many toyota trans have run fine on cheap gl5.

 

[sunrk]

Soooo, on that premise is Mobilfluid 424 a bad choice to use in *both* gearbox and transfer? That's the premise that most of the feedback I'm getting appears to be based around.

 

[maxamillion2345]

Idk I probably wouldn’t, kind of designed for a different application.

 

[sunrk]

Does anyone feel that the Redline products (MT-90 for gearbox and Heavy Shockproof for transfer) are actually worth the money then? Up to know I've tried to avoid different gear oils for the box and transfer, same as I use Castrol LSX-90 in both the front and rear axle assemblies to lube the diffs (no lockers - just std at front and so-called factory LSD [yeah right!] at rear). At present the box and transfer both have Castrol VMX-M (box also has Nulon G70 additive).