Firstly, I've had my 98 Cherokee Classic for 3 months and have no clue to full maintenance history of her... I changed my oil shortly after getting it, replacing it with Royal Purple synthetic with matching filter. I've replaced the battery and starter as well, she runs great but I noticed oil/grease (?) from my rear differential and want to replace the fluid and gaskets in my front and rear. I've thought I would also change the fluid in my transmission and transfer case while I was at it. Any help on what fluids are best, I would prefer to put synthetic in anything I can to help prolong the life, I have 186,000 miles and want to get another 100k atleast. I tried searching the forums and found some answers but it left me with more unfortunately. One said not to have the transmission flushed if it had never been done before.. is this true? Any help will be greatly appreciated, thanks in advance.

 

I would advise to clean the outside thoroughly and determine where the leak is coming from before changing the gear oil. It could be the diff cover or could be the pinion seal. If its the seal, you'll want to fix before changing fluid.

As for transmission, they were probably referring to a power flush. No need for this, just dump the trans fluid and refill with some Dex/Mer III assuming you have an auto tranny. If it looks really bad like it has never been changed, you probably want to drop the pan and clean the magnet off and maybe replace the filter/screen. Note this does not replace all the fluid in the system. If its bad, you probably should do it again after a few thousand miles.

 

Don't forget the cooling system......easy Saturday afternoon job while all the parts stores r open and <$250 in parts, including a new rad. Do not take the XJ cooling system lightly.

Do a search and check out salad's superb motor oil thread......u may change your mind about Royal Purple

 

Absolutely agree with djb's comment on the cooling system. It's a good investment and since you have no clear maintenance history, it might have been neglected for a long long time.
A tune-up will be another thing to consider. Total costs will be very acceptable for this job and you'd be good for several thousands of km's/miles.
After cooling system, tune-up and all fluids, the essentials are covered. If you have time and money, the list can go on