I just recently got a '01 2500 HD with 126k on it and have a couple of questions.

First, when I hit the tow/haul button nothing happens, at least the dash board light doesn't come on. I haven't driven it after pushing the button so I don't know if it's engaging, or could I even tell without pulling a heavy load? Any insight as to where to start looking?

Also the sticker says it came with a locking axle, but spinning the wheels in gravel shows only one wheel to be turning. Am I missing something here?

 

You could have a bad dash tow light.

You should notice a difference in the RPM's while driving. The tow advantage shifts the transmission later and there fore keeps the RPM's higher until it shifts.

I cant offer any help concerning the lockers except check the glove box for a owners manual.

 

I have a 2002 2500HD and the only time a notice a difference in the Tow/Haul mode is when I am pulling a load. It will let the motor rev higher before shifting to the next gear. Also, your dash light may not be working correctly.

 

Ihave a 04 2500hd 6.6 turbo diesel and u can tell if it works by when your slowing down it downshifts harder to helpyou slow down eaiser with a load. Just get speed up to about 60 and hit the tow haul mode andhit the brakes anddown then do it with it off you should feel a difference in the way it downshifts.