I would change ALL the fluids:
and if that wasn't enough
power steering fluid and brake fluid
I like to use Mobile 1 synthetics in the diffs, and synthetic blends for the engine and tranny. Most people sasy that putting synthetic in a motor that has been using conventional oil may find leaks, that and the price is what makes me get the blend. I'd suggest getting the Prestone Flush kit from any autostore and flushing out the rad and crap, it does a really good job, but that connector they sell isn't that long lasting, mine lasted about 3 years, but for the money it was so worth it.
97 XJ - Black Sport, 4.0L AW4, D30 and 8.25
6" Skyjacker/RE, 33x13.5 Swamper LTB
Cracked Frame, good for steering!!!
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