Thread: LT95 gearbox oil .... again.

Yep. I know they are different boxes.

So how is it ok. I'm wondering if the faster spinning shafts and gears that would cause the oil to foam are near the bottom of the box and completely submerged in oil. That would not allow air to enter the oil and therefore no foaming.

I was hoping someone would comment on how these boxes differ in design.

Happy Days

Originally Posted by joel0407

Yep. I know they are different boxes.

So how is it ok. I'm wondering if the faster spinning shafts and gears that would cause the oil to foam are near the bottom of the box and completely submerged in oil. That would not allow air to enter the oil and therefore no foaming.

I was hoping someone would comment on how these boxes differ in design.

Happy Days

For starters, the gears in the LT95 transfer case are loaded up on the shaft with shims. The shims have grooves in for lubrication and cooling. When an oil that is too thick is used, the oil doesn't get into those shims, they overheat, burn and bind.

OK, for those interested, a pic of the mainshaft 'wear'.






Cheers,
Daryl.

That is serious wear Daryl. There is no way that the bearing would be still ok running on that. My guess is that the bearing has been replaced recently, knowing the vehicle was being sold.

Brian, you might be right there, as I thought that the reduced radius of the shaft might have at least cracked the plastic roller cage, but it was intact and uncracked.
Also, the rear plate was easy to remove ... no prying required.


Anyhow, we'll wait and see what happens with the Penrite Pro Gear, but so far it shifts 300% better than 20w-50 engine oil, which made 3-2 shift totally out of the question without double shuffling and half the other syncros weren't much better.



Cheers,
Daryl.

...Put gear oil in it and you'll be changing the transfer case gears more often than the oil.

People who make blanket statements like that show they have no knowledge of modern gear oils.

Originally Posted by Mick_Marsh

For starters, the gears in the LT95 transfer case are loaded up on the shaft with shims. The shims have grooves in for lubrication and cooling. When an oil that is too thick is used, the oil doesn't get into those shims, they overheat, burn and bind.

You know the perenties have the TR bearing case???

Originally Posted by circlework

Anyhow, I've swapped the box out and I'm using Penrite ProGear 75W-90 synthetic in both Xfer and main.


Cheers.

That'll be fine, although I'll be interested to hear how it shifts, the TDS claims it's formulated for manual gearbox use.

FWIW a 75W-90 is equivalent in viscosity to a 15W-40 engine oil all the way up to 100*C (and beyond)

Originally Posted by joel0407

Yep. I know they are different boxes.

So how is it ok. I'm wondering if the faster spinning shafts and gears that would cause the oil to foam are near the bottom of the box and completely submerged in oil. That would not allow air to enter the oil and therefore no foaming.

I was hoping someone would comment on how these boxes differ in design.

Happy Days

Joel, it isn't the detergents that create the foaming, any oil will foam, but they need specific additives to prevent foaming.
In engine oils this takes the form of a silicon oil, in gear oils I think they tend to use an ester polymer as the silicons can entrap air in the form of lots of tiny air bubbles (without the total milkshake effect)

Probably another reason why engine oils really have no place in gearboxes.

Engine oil was originally specified as back in the day gear oils weren't available with the wide viscosity span that a 15W-40 engine oil posses.
They just didn't flow well in a cold ambient.
These days specific manual gearbox oils are available that don't don't corrode brass synchros, and give better shift performance with those same synchros as they use specific friction modifiers for synchro use while protecting gears and bearings better than an engine oil can.