I wanted to add a few things.
So, when you are in reverse in 4WD, then put it in drive, what happens? Does it stop moving?
This could be an internal failure of the transfer case and causing it to bind. Might want to check for any metal shavings on the fluid.
Also does it make any noise while in reverse and in 4WD?
It is possible that the internal components are binding up wile move forward and not allowing the vehicle to move with the 4WD engaged. Typically, this will create metal shavings along with other metal fragments.
Check the fluid condition thru the check plug on the transfer case. If there are metal shavings it will be easier to see form, there.
I have attached diagrams below for your reference.
Please let us know what you find.
Wednesday, March 9th, 2022 AT 6:26 PM