diff oil

[wranglertj]

It is time to change my diff oil.
Problem is the manual says sae 80w-90 but i queried this as i have the rubi and didnt stipulate any difference in oil if have the trac-loc or tru-loc (as in the rubicon). Jeep told me not to use the 80w-90 which i beleived to be correct (hence why i queried) and they told me to use Castrol SAFXA 75w-140 with a limited slip friction modifer which you can only get from Jeep for $15 a bottle for each diff.
I ended up getting Nulon 80w-140 fully synthetic diff oil with limited slip additives (so i dint use the Jeep additive). Good stuff but bloody expensive
WHat are you guys using?? Do i need to go to this extreme??
What are other Rubi owners used for their diff oil?

Cheers

[davidd]

80/90 is for normal light or road use. the synthetic 80/140 is for offroad towing heavy duty use. a really good choice in a 4wd that is given a bit of use. worth the money. absolutely worth the money.

[double black offroad]

Originally Posted by davidd

80/90 is for normal light or road use. the synthetic 80/140 is for offroad towing heavy duty use. a really good choice in a 4wd that is given a bit of use. worth the money. absolutely worth the money.

Why absolutely worth the money?

[Keith]

Originally Posted by bigsuzi

Why absolutely worth the money?

Less wear on the gears under severe conditions.

[wranglertj]

Originally Posted by davidd

80/90 is for normal light or road use. the synthetic 80/140 is for offroad towing heavy duty use. a really good choice in a 4wd that is given a bit of use. worth the money. absolutely worth the money.

i guess it cant do any harm. Its a bit of dough though but happy to spend this money if it keeps it in good nick as i do use it regularly for off road use and not afraid to use it how it was intended.
I was curious though if this was a better bet over the non-synthetic diff oil?
I know it is a better oil but would you not recommend the use of a non-synthetic?
Thanks

[Yom]

I would have imagined the lighter oil would be used in the diff lock equipped diffs otherwise the thicker oil could cause problems with the lock activation when cold.

oil viscousity has little to do with the amount of lubrication an oil can provide these days. i think thicker oils in diffs are more to quieten them down for joe blog end consumer who doesn't like hearing any mechanical noise.

Does the LSD oil actually matter? I didnt think the JK had a clutch type LSD i thought it was electrical courtesy of the ESP?

[davidd]

yep, synthetic doesn't break down like normal oil (over extended time) and it's viscosity is more constant, and doesn't vary as much with temperature changes. had it put in mine at 20,000 service.