OK got to the 500 mile break-in on the new 5.13 gears so here's the question.....Live in South Dakota (cold winters and hot summers)....HAVE 4 DOOR RUBI..What Mobile 1 synthetic gear oil. 75/90 or 75/140?????

 

what does your manual say ? Fill up your Jeep JK Wrangler’s front differential with 2 quarts of SAE 75W-90 synthetic gear oil. DO NOT be tempted to fill up your differential with anymore gear oil or else it will get pumped out of the breather tube and make a big stinking mess.

 

Go with what the manual says.

The lighter weight in both.
The 140 weight in the rear if you do heavy off-road or towing

 

Yes I know not to fill them to much but I was thinking the 5.13's would run hotter down the highway and the 140 would keep them cooler. Am I thinking right?

 

they say to use 140 for towing only in the rear diff. i will be going that rout at next change.

 

when adding in 5.13 gears, do I need to use less oil in the front for any reason? I keep adding in the same amount of oil as before the gears, but it seems to always have some come out the breather and makes a mess?

If I add to much Gear Oil, will anything else happen besides it come out the breather, like leak out one of the sides of the axle? Anything else?

 

Where in the manual does it say two quarts? i found what fluid to use but never saw the capasity

 

This was taken from the Project JK....The front takes ~ 1.35 Qts, rear 2.375 Qts

http://project-jk.com/jeep-jk-write-...hange-write-up

 

No, go with what the Owners Manual recommends. If you don't tow use the 75W-90.

As the manufacturer recommends the 75W-140 is to help protect the gears from the extra pressure put on the surface of the gears when towing. FYI - the shop that installed my 5.38 gears down here in pretty hot Phoenix recommend the stock 75w-90 weight.

 

for the 2010 it recommends 80w-90