2015SSilverado

Great feedback on my differential. Thanks so much txab for the AMSOIL product referral. It has not been serviced before to my knowledge. It is a 12 Bolt diff with Service Parts Codes for G80 (diff) and GU6 (3.42 ratio). Drained and measured 2.5 Quarts (give or take an ounce) of fluid without metal particles or flakes. There was a light residue inside of the cover (dark gray in color) which wiped off easily with paper towel. Ring gear showed no apparent scuffing, chipping, or cupping. Good initial impression. It is a PosiTrack diff with slip modifiers already in the lube, right? You mentioned, "You use NO ADDITIVES in a G80." So does the AMSOIL Already have the needed friction modifying additives? Please advise if there is any issue with the additives already in it per the spec sheet for AMSOIL Severe Gear 100% Synthetic Gear Lube regarding use in the G80 diff. I very much appreciate your reply and suggestions. If the Mobile 1 use seems better would it require additives? Any torque spec for cover bolts? I've seen various statements from uncertain applications from 25 ft pounds to 20 ft pounds + 20% turn. Capacity and fill is still unknown, but my impression was somewhere around 3 quarts. Should it be filled to the bottom of the fill hole? Some systems might be about 1/2 inch below the bottom of the fill hole.

How hot does the engine temp get in the afternoon when it goes up?

P.S. There is a temperature sensor near the thermostat. The thermostat and coolant temperature control the fan starting and stopping. I wouldn't rule out that temperature sensor near the thermostat.

Wow! That can get expensive. The radiator has two Transmission Fluid lines (One to send hot from the transmission as it goes through then another one to return cooler fluid back to the transmission). If any of the radiator hoses are soft or leaking, then it's time to replace all of them. Coolant reservoir should have a full mark on the outside of the container. In my 2015 Silverado Crew Cab 5.3L, I had both fans run for 5 minutes (or longer) after turning off the engine. It was fixed by replacing the thermostat (part consists of stout hard plastic hose fitting with a thermostat inside. My first clue was the fan running fast while driving then even after turning off the engine. Look at the temperature gauge which should be straight up in the middle. With your climate, If driving is stop and go, then higher temperature coolant could be normal. Highway driving will send a lot more air over the radiator to remove heat. Check mixture is fresh with 50% antifreeze and 50% distilled water. Be sure the coolant is maintaining pressure (little below 15psi is normal) Too much pressure causes leaks. You should be able to get a pressure test kit (loaner tool) at Pep Boys, Auto Zone, or O'Reilly's to see if system is sound. Does the engine run smooth? Hope this finds you more success.

Rear Differential 2015 Silverado Z71 Binding Seems that the rear wheels try to turn at different speeds while driving straight on level ground. Intermittently can cause light, but immediately noticeable pull of steering wheel toward right. More often occurs from stop during sharp turn to enter traffic at an intersection. Might continue pulling for 1/4 mile to 5 miles. Sometimes does this on highway at 70 MPH. 105K miles on vehicle. Yesterday, rear wheels were screeching lightly as I drove around traffic circles or turned at an intersection. Are there any preferred lube and additive for the rear differential other than the 75w 90 and limited slip additives?