Gear Oil Viscosity

TomJK

TomJK

New member
After reading Eddie's write up on changing differential oil, I felt inspired to do my own, only to discover there are various viscosity ratings... Which makes sense. I've looked around to see what my 08 JKUX with stock Dana 44s takes, but can't find a constant answer. Does anyone have any recommendations? I do mainly on road driving, no towing, and get out off roading 1 or 2 times a year, if that makes a difference. Thanks for any insight!
 
Just get It from the dealer. Little bit more expensive, but you've got piece of mind. I screwed around for a while with some other stuff & just switched back.
 
Learned the hard way the importance of changing. Was at 19K and had a great day wheeling minus my rear lockers not disengaging. Experienced Jeeper found the problem to be too much metal fragments keeping it engaged. Manually disconnected through fill hole at an angle. Easy to change. Always good to wheel with friends.
 
TomJK said:
After reading Eddie's write up on changing differential oil, I felt inspired to do my own, only to discover there are various viscosity ratings... Which makes sense. I've looked around to see what my 08 JKUX with stock Dana 44s takes, but can't find a constant answer. Does anyone have any recommendations? I do mainly on road driving, no towing, and get out off roading 1 or 2 times a year, if that makes a difference. Thanks for any insight!
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Just use what you use for motor oil in terms of brand. I use Mobil 1...hasn't let me down yet. Insert oil company here usually works fine as well when it comes to gear oil. Regarding the viscosity/weight, depends on if you have LSD or not. 75W-90 is usually used up front and 75W-140 in the back if you tow, but these days the newer JKs are calling for heavier 80W.

I'm actually about to change mine here soon so I need to figure out which one I am going to use this go-round. I used 75W90 on my 07, but on my 15 I might use 80W90.
 
H8ROADS said:
. 75W-90 is usually used up front and 75W-140 in the back if you tow, but these days the newer JKs are calling for heavier 80W.

I'm actually about to change mine here soon so I need to figure out which one I am going to use this go-round. I used 75W90 on my 07, but on my 15 I might use 80W90.
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Unfortunately I saw this after I got my oil. I went with 80/90 for LSD, since I wasn't sure if mine was LSD. Anyway, I just added the 80/90 to the back, and drove it around the block. But now it's not feeling quite right. Hard to describe, but there seems to be a slight shutter or something. Is that normal for new oil? Or could the 80/90 in back be a problem?
 
I did 75w90 75w145 mobil1 my last change at the 50k mark. No difference in driving you should probably pull your cover off and check it out.
 
Well here's to hoping a switch to 75w145 in back will clear it up. I'm wondering if the change exacerbated a problem I've suspected in the spider gears. A few years ago I had a rattling in the differential, which the dealership said was a spider gear issue. They supposedly fixed it, but it returned a month later, and has been around since. There certainly was a lot of debris on the magnetic plug. I guess I'll find out with the cover off... So much for saving money and time:doh: Haha
 
Eh you know limited slips require a friction modifier. If your oil didn't have that bad stuff could happen.
 
Pyro1415 said:
Eh you know limited slips require a friction modifier. If your oil didn't have that bad stuff could happen.
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I was actually aware of that, so I made sure to get synthetic labeled as "limited slip", just incase, since I'm not sure if mine is an LSD or open.
 
In a new development, I had the brilliant thought to actually check my users manual... And go figure, it has a recommendation. For the rear differential page 426:
198RBI(Model35)and226RBI(Model44)-MOPARGear&AxleLubricant(SAE80W-90)(API GL-5)or equivalent.For trailer towing,use MOPAR Synthetic Gear&Axle Lubricant(SAE75W-140) or equivalent.Models equipped with Trac-Lok™require an additive
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Now since I used the recommended 80w90, I'm back to wondering the cause of this slight shuddering (really, I cant describe it exactly, but it just doesn't feel right). I don't know if it was the "API GL-5" type, or even what that is. I'll have to check the bottle, tonight.
 
TomJK said:
In a new development, I had the brilliant thought to actually check my users manual... And go figure, it has a recommendation. For the rear differential page 426:

Now since I used the recommended 80w90, I'm back to wondering the cause of this slight shuddering (really, I cant describe it exactly, but it just doesn't feel right). I don't know if it was the "API GL-5" type, or even what that is. I'll have to check the bottle, tonight.
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I hope you're not still driving it man. Gears can go bad quick
 
Well I've had to use it, since it's my only vehicle. But yesterday, I took it for another short test, and the shudder was gone. It hasn't returned since, so I'm guessing the gears just needed to get recoated in oil, perhaps. On an odd side note, the rattling I've had also went away.... For a while. It returned after several more miles of driving, but it lends credence to my belief it's inn the differential. I'll have to open it up next week.
 
True story. Mine just keeps making them nowadays but gear oil is an easy project that shouldn't do anything really.
 
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