2001 XJ with 170k. Yesterday I checked the differential fluid and it was brown. Looked like mud. I'm guessing it has never been changed since bought new. What's the best differential fluid I can get? I've been reading mixed reviews. I don't do any towing. I drive it daily on the highway about 30 miles everyday. I'm running 31's on 3 inch lift. Also what's the best TC fluid out there?

 

Md3 atf in the transfer case. For the diff I run 85w-150 delo 400. Change it at 30k like your supposed to and the fluid doesn't need to be expensive.

 

The differentials and transfer case aren't that picky. Way more important than "brand" is proper change intervals.

Use a name brand diff grease and you can use the same Dex/Merc compatible transmission fluid that you use in your automatic AW4 transmission. If you don't have history of transmission fluid changes, change it at the same time as the transfer case.

What is the history on routine cooling system maintenance? Critical that you have fresh antifreeze circulating in your engine as well as a swap of any and all of your original cooling system parts at 170k, if they have not previously been replaced. Money spent on your cooling system is probably the best money you can spend on your XJ!

 

I've put on a new radiator,hoses and thermostat. I'll be dropping in a new water pump in the spring.

 

All I can say is excellent advice, it will save you money to do these!

 

Agreed with the above.

I just changed all these fluids on my XJ with 202k miles. I used Valvoline gear oil for the diffs, just because thats what the store had. I used Valvoline Maxlife Dex/Merc ATF in both the trans and transfer case. Several thousand miles later and all seems good. It's supposed to be compatible with most trans fluid recommendations.

 

I use Valvoline Full Synthetic 75W-140 in my differentials. Since you have 31s, I would recommend that for you.

The 31s put more stress on your gearing, much like towing.

I use Dextron VI in my AW4 transfer cases. Dextron III is also acceptable. VI is a newer formulation.

 

Own an '00. Daily driver, no towing, no limited slip. Ran regular NAPA GEAR OIL 80W90 part # 75210 until recently. In an effort to improve gas mileage switched to Valvoline VV975 75W-90 Full Synthetic Gear Oil. Caught a sale and got it for $7 a quart. Used a little over 3 quarts. Used some of the info here:

http://www.jeepforum.com/forum/f11/m...5-ats-1551782/

Still just run Dex III in the TC. Might swap that out to a synthetic at some point. Used this as a guide for the diff fluid change:

http://www.4x4xplor.com/diff-service.html

Also did not use diff cover gaskets. Used NAPA Gear Oil RTV Sealant BK 7651944.