Positraction Condition Testing - Ford 9"

[ashmatk]

I am shopping for a 28 spline posi for my e-bird project and have an opportunity to a pick up a rebuilt one locally, but I have a question: Does anyone know of a way to test the condition/strength/etc of the posi unit while the differential is still in the car. Is there a way to lock one component, like a tire or the yoke, and attach a torque wrench to the free wheel? The guy's price is not cheap, so I am hesitant to buy this thing if I'm going to have to do a full clutch rebuild. Any advice would be greatly appreciated.

I also posted this same question in the early bird section, but I realized I should have probably posted it here. Sorry for any confusion.

[Darel]

You got it right, you need to block one end (try wedging a bar crosswise through two of the studs so it rotates into the ground) and put a torque wrench on the other. I don't know what kind of posi these cars had, but if it's a Trak-Lok it should break free at 90 ft/lbs. Other LSDs may be different. One thing - they say in order to get an accurate reading you should use a beam-type wrench instead of one of the clicking kind, although I doubt you care too much about accuracy as long as the diff breaks away above a certain level.
Darel

[Darel]

I should qualify that - a NEW or otherwise lightly used Trak-Lok should break away at 90 ft-lbs. I would bet anything over 60 is still pretty good for a 40-year-old car.
Darel

[Darel]

OK, I finally got my service manual in the mail. It states that the equa-lok diff should break away at 100 ft-lbs, anything less and it should be rebuilt. Sorry, I guess I was off initially.
Darel

[SCUMDOG]

So how do you tell if your T-bird has a 9" or a 9 3/8" rear-end?
My car is a '66 and it has a posi of some sort.

[Harley Eaton]

I think you will find that the 9-3/8 " Ford rear end did not come into servive until the C-6 transmission was used.