Hey everyone so last night I was trying to diag a grinding noise I get from the drivetrain while driving. Last week I replaced the trans and t case adapter because it cracked. I changed the fluids and found some slivers of metal. Now I have some fluid on the passenger side of the case.When I was switching from 4 low to 4 high my truck made a grinding noise, all lights on the t case dial turned off and I got a service 4 wheel drive message. Now my speedometer is reading 80 when I'm doing 25 in 4 low.
I've tried unplugging the decoder, and front axle actuator and disconnecting the battery to no avail. I'm at a complete loss. Truck is a 2007.5 2500hd 6.0 6l90e.

 

Sounds like you have a busted transfer case to me. 4 wheel low gear can really harm things unless you take it easy. Looks like you have a lot of money in your pickup. Did you come to a stop to engage and disengage the transfer case into and out of 4-low?

 

I'm in agreement. I've never used 4 low. Transfer case aren't that bad to replace. You might remove the shift motor from it, and manually try to shift it out of low.