Servicing my 2012 GMC 2500 6.0

[MORSNO]

I am the original owner of a low mileage 2012 GMC and am looking for advice on what servicing you'd recommend.  The truck just past the 70,000 mile mark (less than 6,000 a year) and has been flawless so far.  It has never had to go back to the dealer or shop for anything so far.  I've changed out the tires twice, replaced the battery twice, replaced the shocks with Bilstein 4600's, do regular oil changes and grease the front end myself, and replaced the air filters a few times.  I was thinking of changing out both differentials with synthetic lubricant, drain and refill the transfer case, drop the transmission pan to replace the transmission filter and replace fluid, and finally drain and refill the engine coolant.  Anything else, or any of these you would hold off on?   

Edited September 2 by MORSNO

[diyer2]

Brake fluid.

[carkhz316]

Power steering is an easy one, and often overlooked.