I installed a new lockright yesterday in my '68. There seems to be a problem though, when going in a straight line and I hit it where it previously would have just broken one tire loose, it now accelerates alot faster but leaves skid marks, and when I go back and look, they appear to be alternating skid marks of about a foot in length. If I let go from a stop I get two solid lines of rubber. I'm concerned because it would seem to me that this is something like axle hop but I don't know.
I have traction bars, multi leafs, subframe connectors, the rear is the 8.2" ten bolt, a 4 speed and I thought it was a 3.36 but the numbers on the ring gear were 37 12 so I guess its a 3.08 (no speedo to measure) the tires are 245/50/16 on an 8" wheel. I have somewhere probably just shy of 400hp. Any help before I blow my rearend up?

Did you check the gap between the drivers to see if it was correct? If the gap is not right the locker will not work properly. If the differential case is work inside then the gap will be too wide and it will not lock up, or may unlock at times. The case gets worn by doing one wheel burnouts.

I didn't check the gap with a ruler but it looked less than 5/32 they said was tolerance, I guess it could have close.
I am runnig a 75w-90 synthetic oil, would that have any affect?
assuming that it is a worn case, can I get bigger thrust washers to fill in a little bit or do I have to get another case and reset the gears?

I don't know of any thicker thrust washers. As far as I know they are all about .030. If the case is worn then it should be replaced. The oil will have no effect on a locker.

maybe this is a stupid thought but could I use two thrust washers on each side if I have too much gap when I take it back apart? I don't understand the purpose of the thrust washer or if this would have an effect, I really don't want to have to pay someone to reset the gears though.

It may only be worn on one side. The space on each side needs to be the same. If the space is not the same then one side will be doing most of the work and it might not work right.

heres a stupid question did you call lockright tech support?

its on the instruction manual.

I have tried but the first number 1-800-lockers in the manual goes to some [gym] locker manufacturer and I wrote the other number down wrong yesterday at home to call at work because they were closed when I tried to call. I give them a call in the morning see if they have any ideas

I finally got ahold of Tech Support said they had never heard of this type of problem, usually if the case is worn one side unlocks as pressure builds on the pinion shaft.

They gave me the measurements and tolerances for the pinion shaft and said that he had heard of the pinion shaft being off center by a few thousandths. but it stumped them too.

I'll let you know what the problem ends up being

and if anyone has any other ideas let me know