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?

 

If you pu it in tow haul mode, a light tat looks like a trailer should show on the dash. You can also tell by the fact that it will hold second gear till you hit 40 mph, whereas it normally would shift sooner when just cruising.

As far as the locking differential, it only engauges in 4wd low.

 

no, I can get the diff to lock in 2wd on wet grass. Both my chevys have done it in 2wd.

 

That may be the limited slip, 2tone. In 4 wheel low it feels like the rear end is one solid piece. Your light may be out on the dash. Try driving it after pushing the button and listen for what Smoke said. The shifts will be firmer as well. If you are unsure how many times you've pushed the button don't worry, it defaults to "tow off" when you turn off the vehicle.

 

limited slip? on a chevy, Z71 at that? There's no way for the rear diff to know you're in 4WD hi or low.

The major difference in two/haul is the extra time in each gear, and firmer shifts. Firmer shifts are actually good for you tranny. Helps with the heavy loads.

 

This looks like limited slip to me, but, there may be another name for it.

 

the toyota is limited slip, the chevy is locking. A limited slip will transfer torque to the other wheel, while the locking diff will lock both sides together and spin together. givaway - with the chevy with onw wheel in the air, it spins while the other is stopped, I don't remember how many turns it takes, not many, and the other locks like a solid axle. much more effective than what the toyota has, as is proved in the video. The going back and forth is a product of limited, just transfering torque.

 

There are electronic locking differentials that can be turned on manually, from a switch in the dash, or automatically, through another item in the driveline. If Chevy uses them on the 2500 HDs, I don't know.

 

i've seen a couple of tow switches bad..thats probably it

 

Is that a tough item to fix? I'm not sure I'll ever really need T/H mode, but it would be nice to have it working.