I have a '66 coupe that i've only owned for a little over a year, and the PO didn't know too much about the 40 years of work that had been done to the car.

How can i tell if i'm running with the stock rear end, or have after market gearing or a locker and what not?

Looking? measuring?
thanks for the help

 

Jack both rear wheels up and spin the tire.
Spin forward and backwards to check.
If they go the same way its a posi if opposite its open.

Look for a tag on one of the bolts on the center chunk should have numbers stamped like 2.80 3.25.3.73

If not turn the tire and count how many times the yoke spins to turn the tire once.
LOL I forgot the ratio count but do a search to find out.

Most i have seen are open diff with 2.80 gears 8"

 

Alright thanks man that should be everything i need to know!

 

Any time Dave.
I've been wrenching on mine for the last 2 days and about to bring home my next project.
It is amazing how much info is available now.
25 years ago when I had my 1st car 69 falcon it was trips to the library going thru old Chilton manuals.

 

That's what my dad was telling me

He said it would take him like a week to find out information i can get in half an hour [8D]

 

There's a little tag held on with one of the bolts on my rear axle
Has a few numbers on there that were slightly readable
Does anyone know what they mean or where I'd decode them or something? If so, I'll go try to salvage what I can

 

hit it with a wire brush then go search for the decoders it will tell you what you need to know.
should have a number tho ?.??

 

Didn't see one right off the bat, but it needs a little cleaning before I can really read it

 

Clean it up and look here http://www.fordification.com/rearends-ford.htm

 

To know for sure, you could count the teeth. But, don't spin a tire and count the yoke turns. That isn't likely to work with an open rear. Turn the driveshaft and count the number of turns on the driveshaft it takes to turn the tire once. That's your ratio.