This is what gets me the truck was a 390 from factory, now the rear end is a 9 ford rear end, but no tag I spun the drive shaft one time and the tire was already a half a quarter to one revolution but it pulls to hard off the line to be a really tall gear and turns 2500rpm at 55mp but their ain't no slippage and the its shifting info 3rd, so I'm lost checked my tack changed it and it was dead on so I'm at a loss