What exactly does Sport Mode do?

[Left Coast Geek]

I mostly only use 4A on surfaces like wet grass or dirt at very low speeds when towing... Like entering or leaving a campground....

 

[ryoung57]

Update. Problem seems to be solved. The selling dealership put a new transfer case clutch in it (messing up the gasket in the process) and it still shook. My local dealership put an all new transfer case in it and changed out the IWE on the drivers side hub. It wasn't as bad, but still didn't feel right. I lifted the truck and crawled under when running to check to see if the hubs were disengaging in 2H - they were not. I dropped if off at the dealer and after a whole day of messing with it, they "couldn't replicate the problem" (morons didn't even understand how the IWE system works). So I had to do it myself. Ten minutes with my mighty vac to see where I had and didn't have vacuum led me to the IWE solenoid on the firewall. I'd been driving around for the last year with the hubs locked in. $40 and 2 minutes of work later and it's perfectly smooth.

 

[newyorkistansux]

Glad you figured out the problem, how are non-mechanics supposed to do that level of troubleshooting?