Buying an old Melton truck, need advice

I found a used 2012 T660 at a lot in Seattle that looks identical to Melton-spec trucks. With it already having a raised fifth wheel and an APU, it's suited for the tankers I haul.

One thing that raised a concern during the test drive were how awful the super single drive tires are at spinning out. I've driven trucks with SSs on them before and never had these problems. Ground was dry and I had to leave the diff lock on (glad they had them) to get any traction.

I run routes with mountain passes, snow, and ice. Current Melton drivers: do you have any significant problems driving in slippery conditions with these drives when fully loaded?

Also, I noticed a key/lock mechanism on the dash in between the center gauges. Any idea what that's for?

 

Okay, thanks. I wonder if the auto traction control is faulty or something. I adjusted to it after a while, but it was a drive like none other I've had.

 

I think I've found out why. Melton trucks are apparently equipped with 2.64 rears - something I'm very unfamiliar with. I think if I adjust how I shift I'll be fine.

About what RPMs do you typically upshift at?

 

Thanks! I'll try that.