Is it necessary to change the diff. oil?

[artificialist]

It depends on the rear axle design.

I see many rear axles that never received a single fluid change and have 200K+ miles on them, and I see others that need repair at 100K miles.

So I replaced the gear oil on my mom's Jeep Grand Cherokee at 11,000 miles because the Manual said 12,000 mile intervals in harsh conditions. That or 50,000 miles in easy conditions. This thing takes 75w140 synthetic gear oil!

 

[webfors]

Subaru manual stated every 72k km for diff and manual transmission. I changed mine at 16k and it was filthy, viscosity was off, wear metals off the charts, definitely not worthy of a 72k km service interval. The magnetic drain plug was completely *full* of wear metals.

I changed it to Motul Gear 300 at 16k km, drove it for 30k during the past year and just changed it out 2 weeks ago to Gear 300 again. This time around the fluid looked excellent and there were *no* wear metals on the plug at all. I was seriously impressed with this gear oil and will continue to use it for 50k intervals with confidence.

If you want to go lifetime on the diff, drain out the factory fill around 10k and then use a quality fluid.

 

[bigmike]

Originally Posted By: Popinski
I've seen several owner's manuals and they all stat that it isn't necessary to change the rear differential oil. Why do people still do it and how often is there a rear diff casualty?


On one of my trucks, the rear driveshaft locked up on me driving 70MPH on the interstate. I never once saw a drop in my driveway, yet there wasn't hardly any fluid left in the differential.

Needless to say, it isn't fun. Cost $600 to cover the repair as well. This is why changing it is a good idea - if nothing else make sure there is no leaking.

 

[jayv]

FYI,
my land rover discovery II has a recommended first diff cgange at 6 months or 7500 miles , then at 72 months or 90000 miles, while my 06 rubicon unlimited has 15000 miles interval changes.

in the land rover i do it every 30000 miles while performing other 30k routine maint.