Idk, I know they reccomend a hard to find synthetic (I remember going to a few places to find the specific weight In synthetic) but I don’t remember anything about needing a friction modifier like my old ranger needed.
Nope you just connect it to get your factory tune, then you will plug it into your computer to send them your stock file, they email you your tuned file, plug the tuner in, upload tune to your truck then your done!
I’ve got the same noise, at 164k now had it for probably 10k miles. Idk what it is I attributed it to turbo brake from the off road tune resonating in the exhaust. I’d think pinion bearing but if you’ve replaced that then maybe transfer case noise?
This light can be caused by pretty much anything from an engine issue to something in the body control module. I’d try to get a scanner that can connect with all the modules and check for other codes
I did the rough country leveling kit. Lot of guys do the bilstien(don’t know correct spelling but think that’s right) adjustable shocks maxed out and haven’t had issues
Look into alfaobd, costs around 100$ for software and obd adapter. I believe it will do a stationary desoot. Either way it’s a valuable tool for these trucks
Put air to it with an air compressor, if the truck goes up they are still installed, if you hear it leak out from under the frame then they are gone. I put a set inside the coil springs of mine and it looks like they go nowhere also lol