Auburn Pro Series differential question.

[82Cecil]

Originally I thought this was from setting up too long between run periods, but after a day at the track, I think my differential has quit being a "limited" slip.

With drag radials I getting a one tire fire in the burn out box (not in the water but on dry pavement). With the rear of the truck off the ground both tires rotate by hand in the same direction.

This is an 8.5 10 bolt differential. installed in 2007. Am I expecting too much?

On a track only vehicle, is a spool ok on pavement?

Thanks