[Ironangel]

Originally Posted by j_cst_10

I doubt we need anyone else chiming in, but I will anyway. I have a couple vehicles with limited slip/posi units and the jacking the car up and spinning the tires with the trans in neutral doesn't really work. In theory yes, but anything with a little age won't respond correctly.

Both vehicles will lay a furious yard or two with both tires, but won't spin in the same direction when jacked up and put in neutral. Pulling the cover is the sure bet or doing a burnout!

Pulling the cover is indeed the "eyes on" best method to making sure you have a Posi or not...On the tire rotation method, if both wheels fail to turn in the same direction and a Posi unit is in the carrier, that unit could use at least some cleaning and a check of the friction plates. I too have had them so loose that the clutch pack preload is not to spec or not even enough to hold the required 40 foot pounds to disengage the clutch pack. In other words, if one tire fails to rotate in the same direction, your posi's slipping. They do require periodic maintenance and rebuilding. On the tag issue...Do you have a pic of that tag? I am not aware of any tags that designate correct units? There are Posi tags reminding owners and mechanics that a Limited Slip unit is installed and LS additive is required. The Eaton Positration unit for a 71 C-10 is EAT19556 and will accept 3:73 and higher numbered gears. Yukon makes an almost identical unit for about 50 clams less. Need a part number as well as a manufacturer of that red hot tag deal? "Pics please" Classic Parts as well as others have the replacement tags. http://www.classicparts.com/1971-81-.../#.Vk_29F5a59k