Which gear oil weight?

[MountaineerTom]

I know the owners manual says 80w-90 for my Unlimited’s rear axle, or synthetic 75w-140 for towing.

Is it ok to use the 75w-140 if you tow very rarely, if at all? That way you’re ready IF you do tow?

 

[Rubicon John]

Of course it’s ok. My manual says the same thing but the diff is actually stamped with the heavier weight. I happen to have the lighter weight in and it runs fine

 

[MountaineerTom]

Just making sure. I guess the front is ok with 80w-90 regardless of towing or not since it didn‘t say anything but 80w-90.

I have not plans for long distance towing or even frequent towing, but I’d like to be ready if I do need to do either of those. I’ve towed my 10x6 utility trailer to the dump a few times to get rid of some limbs and other yard waste and towed my little pack mule trailer around a couple times, but that’s it.

I’m planning on changing out both diff fluids the week after next when I’m on vacation. Just checking before that time comes.

 

[JKP]

Of course it’s ok. My manual says the same thing but the diff is actually stamped with the heavier weight. I happen to have the lighter weight in and it runs fine

It's stamped with the heavier weight because you have the Rubicon helical geared limited slip axle. The manual specs the 75W-140 for the Rubi diff.

 

[Rubicon John]

It's stamped with the heavier weight because you have the Rubicon helical geared limited slip axle. The manual specs the 75W-140 for the Rubi diff.

Pretty sure I checked before purchasing the oil but maybe you’re right. I’m not too worried about it.

edit: You are indeed correct. I’m not sure how I misread the manual, maybe because it said “RBI 44” and I assumed that meant Rubicon, even thoughRubicon 44 is listed after with the heavier weight. Doh! I’m hoping for a re gear soon so I’ll address it then

 

[Jerry Bransford]

I'd go strictly conventional, and an 80W-120 or 85W-140 is fine even when not towing. I run 85W-140 Valvoline conventional year-round.

Why conventional? It was surprisingly discovered that the gears run significantly cooler with a conventional than with a synthetic. Companies like Currie Revolution Gear, and Dynatrac recommend and specify conventional gear lubes for that reason.

 

[MountaineerTom]

I'd go strictly conventional, and an 80W-120 or 85W-140 is fine even when not towing. I run 85W-140 Valvoline conventional year-round.

Why conventional? It was surprisingly discovered that the gears run significantly cooler with a conventional than with a synthetic. Companies like Currie Revolution Gear, and Dynatrac recommend and specify conventional gear lubes for that reason.

A conventional in those weights would be ok for towing too, if needed too?

 

[Jerry Bransford]

A conventional in those weights would be ok for towing too, if needed too?

Absolutely. I tow my tent trailer everywhere I go with that viscosity.

 

[MountaineerTom]

Absolutely. I tow my tent trailer everywhere I go with that viscosity.

Great! Thanks Jerry.

 

[L J]

Is it ok to use the 75w-140 if you tow very rarely, if at all? That way you’re ready IF you do tow?

I've used Mobil 1 and Valvoline synthetic 75w-140 for ten years based on Chrysler recommendation. After regearing with Revolutions I've switched to Valvoline semi-synthetic 75w-140 based on installer recommendation. I don't tow.

 

[MountaineerTom]

I like using Valvoline products too. I looks like the conventional doesn’t have friction modifier in it, so I’d just get a bottle and add to it, right?

I think I read somewhere 4 oz.

 

[Jerry Bransford]

I like using Valvoline products too. I looks like the conventional doesn’t have friction modifier in it, so I’d just get a bottle and add to it, right?

I think I read somewhere 4 oz.

Yes, pretty much any auto parts store will carry it.

 

[L J]

I like using Valvoline products too. I looks like the conventional doesn’t have friction modifier in it, so I’d just get a bottle and add to it, right?

I think I read somewhere 4 oz.

I'm not positive on the amount but yes if you have a clutch based limited slip.