Ummm.
We drove 100% of the 14miles of race in 4wd hi. I have a grizzly in the front (yes D60 but still grizzly). Speeds from 0 up till piston melt down of 82mph. It tracked fine, I think.
As for why your may or may not be doing odd things, the tire pressure was a great point to check. The grizzly has a under cut side gear assembly that unlike the detroit, is very much less prone to unlocking under very little load. You see this on detroit locker equiped rigs in sand hills or mudd hills where you see a front tire 'skip' every now and them while throttle down and very slippery. Thats the side gear unloading on the detroits. The grizzly was purposely built a bit different, so not to have this issue as much.
As for the tracking. I would test it again in a different trail or location and see if it was just the ruts you were hitting or?
In front wheel drive only, you cant really test anything. Even when you think your going perfectly straight and the locker can stay 100% engaged, your likely not.
Let us know what you find though. Sand can be odd to drive is since you get no side lateral traction typically.
