I changed my diff fluid at 30,000 per the recommendation of the Jeep Dealer. I don't know if that is too long. I did learn from the maintenance manual that it should be done after water crossings and if heavy driving is done, earlier or more frequently.
I also bought a hand pump for this job, which as I said, I did myself. It was not difficult but, I tried to use the pump and it seamed as though the fluid, at ambient temperature, was too thick to pump by hand. When warm, after driving, the fluid was easier to manipulate with the pump, ie drawing the fluid out of the diff but, this was not OK for me. I got a suggestion from a fellow Jeeper on another forum, that it's easy to pull the cover to change the fluid and in doing so, you can inspect your ring and pinion for wear. Another thing about not pulling the cover off is that you really can't get all the old fluid and possible metal shavings out, which is far more important to remove than just fluid.
I used a Mopar version of Silicone to seal the diff cover again. This was what Jeep recommended and what was on it when I took off the cover. I can only assume that the Silicone was factory because I bought the Jeep with 14,000 on the clock and there was no known part for a gasket to do this job.
I also found that my rear diff, D35, did not have a screw in plug, but a rubber plug that was not in any way secure and did not appear to be able to prevent water from coming in in a submerged situation. Neither axle had a drain plug that I could find but, the front, d30, had a screw in plug. I have an 03' SE if that helps. I would like to know if there is a drain plug and a fill plug so this job could be easier in the future.
Anyway, hope that helps and if anyone knows about the drain, fill plug issue, let me know. Thanks.
