Synthetic 75-90 for daily driving. If you offroad or tow a lot then use 7-140. The rear differential may have a limited slip, if this is true then you need to add a special additive : Mopar number 04318060AB
Jeep Liberty did not exist till ~02, 03
Refer to owners manual, it will give you mileage frames on when to change fluids.
In the differential
A 2004 Jeep Liberty uses DOT 3 fluid.
A 2004 Jeep Liberty uses DOT 3 brake fluid.
A 2010 Jeep Liberty uses DOT3 brake fluid.
A 2005 Jeep Liberty uses ATF+4
It was an option, not standard equipment.
80w90
A 2002 Jeep Liberty uses ATF+4.
Wiper fluid
Ceck out "what type of automatic transmission fluid is needed for a 1993 Jeep Cherokee sport and in the front and rear differential" on wiki-answers