Changed driveline fluids: Differentials, transfer case, manual transmission

There are threads about this elsewhere on the site but I couldn’t find anything comprehensive on tools and fluids, so I decided to add this.

I spent about 2 hours this weekend changing all the driveline fluids in my 2016 manual JKUR. It has 76K miles so some of them are overdue. Overall it was relatively simple but extremely messy. My all in cost was $131 for the fluids, but I used more expensive Royal Purple fluids. There are definitely cheaper alternatives. I also spent $40 on tools that I didn’t already have.

Tools required:

• 3/8ths drive ratchet for the differential plugs
• 18 mm wrench for the skid plate
• 10 mm hex wrench for the transfer case plugs
• 14 mm hex wrench for the transmission fill plug
• 17 mm ratcheting combination wrench and
• 17 mm nut (also called M10) for the transmission drain plug
• Oil drain pan.
  

Of these, the 10 and 14 mm hexes were the most difficult to find. I eventually found a set containing both in the Home Depot impact tools aisle.

The 17mm combination wrench and nut is needed because there is limited clearance between the transmission drain plug and the exhaust. Put the nut into the wrench and maneuver it under the drain plug until you can push it half out of the wrench and half into the plug. This is why the ratchet is important. With the ratchet you only need to set the nut once.

Fluids purchased:

• 4 quarts Royal Purple Gearmax 75/90 gear oil for the differentials. I used closer to 3.
• 2 quarts Royal Purple Synchromax for the transmission. Used a little over 1.5. This was difficult to fill, given the location of the fill plug. I emptied both bottles as far as possible then combined them and continued filling the transmission.
• 2 quarts Royal Purple ATF4 for the transfer case (this is actually slightly low as the case officially takes 2.1 quarts.