mjm-1957

Guess your going inside.....

Take the rubber plug out on the tail housing and get a mirror and a light and see if the snap ring that holds the rear output bearing is still in one piece. That snap ring can break and let everything move rearward and possibly cause the issue you are having.

If you are in 4w high or low and not getting any action from the front driveshaft im sorry to say you will have to go inside the transfer case. When you had the encoder motor off did you try shifting it manually?I have had a few with broken shift fork parts and also a worn roller that rides on the cam not allowing full motion of the shift fork but it also was grinding, and you didnt mention any noises.

The oil pump is only there to provide lube oil. The clutch pack only is used in auto 4wd.

The clutch pack is applied mechanically.The front and rear driveshafts are locked together in 4 low, thats why I asked what it does in that range,are you sure the front axle is engaged?You should not be able to turn the front driveshaft if the actuator plunger is pushing the shift fork all the way in. You can also take the actuator out and physically move the fork with a screw driver and make sure nothing is binding or broken.Hope this helps.

What happens in 4 low?

They just type in 16-NA-175 and the latest version will come up.It is also listed as document ID number 4526930.Good luck you will need it.

16-NA-175 was updated again on 10/11/18, includes all 2015-2018 M5U transmissions in sierra and yukon and -2019 M5T in the Canyon and Colorado. They have also come out with yet another flush and fill procedure requiring 20 quarts of another updated HP fluid.We are waiting on the tools to convert our trans cooler flusher over to be able to perform this and also waiting on the new fluid.Seems to be in short supply at the present time. Time will tell if this provides any lasting repair. 75-80 % of my time is spent on these pieces of shit. I have never had a ten speed apart yet and they have been out two years already. The eight speeds were lined up for repair the minute they were released. GM should be ashamed of themselves....

You better get a new dealer, absolutely has a filter.

After blow

I am very happy I bought a 2017 Gmc 2500, that truck is absolutely disgusting...What were they thinking?

The rubber plugs are pried out of the calipers and the slide pin bolts are removed, The caliper is hung on a wire you rig up to make sure its not hanging by the brake hose and get it out of your way.The bolts I believe he is talking about, hold the caliper bridge to the knuckle,they are loctited from the factory and can be a real pain in the ass to remove,we use heat to soften up the thread sealer and hit it with an impact gun. Make sure you lubricate those slides and reinstall the rubber plugs.

Two temp actuators,one mode actuator and one recirc actuator.The drivers side temp actuator is on the bottom.

climate control or manual?

Check for codes, a bad seat element will set a code and the BCM can disable all heated seat functions until repaired.