Only the PPs and PIs get the cooling/temp gauge for the PTUs in the 2013+ lineup.
It does seem the PTU is VERY sludgy. You could call around and look for places with a Differential Flush Machine, such as BG shops or Wynn shops. They can get it done right in one shot.
https://www.youtube.com/watch?v=Qi01ZeTj2dIYou could also try this procedure that
AutoRX has up on their site:
Differential Cleaning Instructions
Auto-Rx® Plus is your solution for cleaning differentials, and it works as you drive to liquefy the contamination residue and build-up.
To get the most out of your cleaning experience, we recommend the following easy, step-by-step method:
STEP 1 Into the differential oil reservoir, add 2 ounces of Auto-Rx® Plus per quart of differential fluid.
STEP 2 Drive 1,000 miles and then drain.
STEP 3 Refill according to vehicle manufacturer's recommendation. This unit uses heavy gear oil.
The chemical formulation of Auto-Rx® Plus is the same for engines, transmissions, motorcycles, and diesels. The only difference is in the individual applications.