Your 42RLE is very fussy about its ATF, it must be ATF+4. It cannot be some generic or "super" ATF claiming to be compatible with ATF+4, it must actually say ATF+4 in big letters on the front label of the bottle.

For a simple pan drop and filter change, you'll need about 4 quarts. To do a complete change, you'll need just a shade under 9 quarts.

 

What's the difference between a pan drop and a complete change. Wouldn't dropping the pan let all the oil out??

 

ATF+4 don't forget to clean the pan! (Amazes me how many people don't do this) also a good time to change your other fluids if you haven't already, transfer case (also atf+4 about 1 Qt I believe) and your front and rear differntials (80w90 dino, or 75w90 synthetic, or if you frequently tow 75w140 in the rear).

Me personally I like to change the transfer case when I do the tranny every 25-30k (over kill? Maybe but at my work place we have a fleet of 20 vehicles plus all of our employees vehicles and almost always hear of a tranny failure before an engine failure even though we always did the "recommended" service intervals. It's cheap insurance so I change it more often)

As for the differentials your manual says 80w90 every 12k I'd say that's fine, if you go with synthetic maybe go just a little longer. Pay attention to color and smell when it comes out it might help you judge if you waited too long or couldve waited just a little longer.

Also remember that any fluid or oil degrades over time, Mobil I think says there's a shelf life of about 5 Years on thier lubricants with that said I wouldn't leave any fluid in the vehicle for any longer than that (same goes for coolant as well)

Sorry for the long post just my .02 on fluid maintenance

 

Pan drop will not include the volume in the torque converter and cooler lines.

 

X2, dropping the pan will only change roughly half of the ATF+4.

 

I always ordered this synthetic fluid when I changed it in my Jeep with a 42RLE. It had about 240,000 miles on it when I sold it. Never a single transmission issue and I did a lot of trailer towing.

https://www.amsoil.com/p/amsoil-signature-series-multi-vehicle-100-synthetic-automatic-transmission-fluid-atf/?zo=226468

 

I always ordered this synthetic fluid when I changed it in my Jeep with a 42RLE.

Every ATF+4, as is specified for all Jeep automatics, is a full synthetic. They're all made exactly according to the Chrysler ATF+4 spec which includes them being a full synthetic. Any ATF+4 is perfect for the TJ's automatic transmissions.