Originally Posted By: zuluplus30
Just lots of reading on various Jeep forums and also that lots of the reputable axle builders that specialize in high-pinion offset axles (Currie, Martin, True Hi-9, etc) all are ADAMANT about using a mineral based GL-5 oil and some even go so far as to say synthetic voids all warranties.
Is is a lube thing? Don't know. These guys tend to operate on cause/effect, and it seems that they see a higher than normal amount of failures when people use synthetic lubes, hence their warranty stance.
I would suppose so, and the axle builders' grounds are valid in my view.
Let's say the factory recommends mineral 80W90 (which is an AGMA 4EP/ISO 150 gear oils) or mineral SAE 90 (which could be an AGMA 5EP/ISO 220 gear oils).
When one uses synthetic 75W90 (which typically is a 3EP/ISO 100 gear oils) , couple with 'severe' duty such as off road, frequent start and stop, high ambient etc , it's operating viscosity is low enough to cause mechanical issues for that application, within a 'short' duration after rebuild that the rebuilders somehow can't evade his promise of warranty/responsibility.
The problem here is we humans think 75W90, 80W90 and SAE 90 gear oils are the same.But the hypoid/spiral bevel gears are saying otherwise , IMHO.
Originally Posted By: zuluplus30
On top of that, Amsoil has their own niche product for such applications: SAE 190 & SAE 250 racing gear lubes.
From their own description:
"AMSOIL Severe Gear EP Synthetic 190 & 250 Racing Gear Lube is specifically engineered for high-horsepower, high-torque conditions where centrifugal gear lube sling-off is encountered. This tenacious formulation clings to gears and bearings for maximum protection during shock loading, high G-forces and where pinion gears are installed at steep angles. Severe Gear provides exceptional reliability and extended gear life.
-Protects gears from shock loading and tire shake
-Resists sling-off from G-forces and high speeds
-Clings to gears—high pinion style and at steep angles
-Promotes cooler operating temperatures
-Protects against rust and corrosion
-Extends gear and bearing life"
Now why would they chose to specifically highlight that aspect if all the other ranges of Severe Gear (75w90, 75w110, & 75W140) do the same thing? They don't list these benefits on the Severe Gear pages.
Again, I'm a young pup when it comes to understanding all this, hence why I asked the question. I'm all ears for somebody to set me straight.
Amsoil SRN SAE 190 has a KV@40*C of 381.6 cSt , which falls in between 6EP/ISO 320 (whose KV@40*C range from 288 cSt to 352 cSt) and 7EP/ISO 460 (whose KV@40*C range from 414 to 506 cSt)
Amsoil SRT SAE 250 has a KV@40*C of 493.8 cSt, complying with 7EP/ISO 460 gear oil specs.
Try re-read the above Amsoil statements in the context of differing KV@40*C viscosities of 75W90,mineral 80W90, mineral SAE 90,75W110, 75W140, SAE 190 and SAE 250 gear oils .............. that might help.
JMHO.
