Stock rearend?

[62scfairlane]

What was the stock rearend on a 1962 fairlane sports coupe? What is the best way to tell if a rearend is posi traction or not? How can I tell what gear is in the rearend? Just researching before I purchase replacement parts.

[Len]

Jack up the rear so that both rear wheels are off the ground. With the car in neutral turn one of the back wheels. A posi (and also a "locked" rear) will cause both wheels to turn together.

If you're looking for the ratio you can mark the drive shaft and the tire then rotate the tire exactly one revolution and count the times the shaft goes around. If it goes around 3 1/2 times it's a 3.50 rear. This is not an exact measurement because it's difficult to tell a 4.11 from a 4.56 but if you watch closely you can get a pretty good idea of the ratio. If there are numbers on the housing they may tell you or you may be able to cross-reference them.

Since I learned this info when I was a teen driving a hot chevy, there may be folks that have a better way to tell on this particular model vehicle.

[Phil V]

Stock ford rear ends have a metal tag attached by one of the pig bolts.
another way to tell if the ring and pinion are posi is to jack up just one wheel so its off the ground then CAREFULLY put the car in gear with your foot on the brake. start releasing the brake, if the car is regular differential the wheel off the ground will just spin (won't matter which wheel you jack up). If the rear end is a posi or a locker the car will still try and move with one wheel in the air.

[62scfairlane]

What if you jack up one rear wheel and it turns by itself?

[Phil V]

with the engine running and in gear ?

[Ranchero_65]

Sounds like a open rear to me . If it were a posi or locker type you couldn't turn it or it would be hard to turn. If the one wheel you turned was rather effortless then it is a open carrier ( non posi) .

[62scfairlane]

Is that a good rearend for a street rod?

[Ranchero_65]

Drag racing NO . Cruising around it will be fine. I'll dig out my motors repair books and see if I come up with anything on it for 62 models. Most likely it's a 8" rear. One quick way to check is the bottom 2 bolts that bolt to the housing to hold the pumpkin in if you can get a socket on them it's a 8" if you can't your in luck it's a 9" rear.

[Lost in NJ]

Look at you door data tag.

Under axel you will see a letter or a number. Then look for a decoder online.

Or look for you axel tag.

If I remember correctly a letter indicates posi and a number is an open rear.

The service manual will have all the decoder info also.

[Phil V]

An 8" and a 9" rear end are easy to tell apart just by glancing at them. The center section of the rear part of the axel housing on an 8" is smooth "round" while the 9" has a relatively large bump or protrusion sticking outward (so the 9" ring gear doesn't hit the rear part of the axel housing). The front outside of the ring and pinion pig on an 8" is relativley smooth while the 9" has several casting webs/ ridges that strengthen the pig casting to keep it from flexing and breaking.

[62scfairlane]

What would I have to do to change the 8" open rear end to a 8" posi traction rear end?

[Phil V]

replace the standard differential pig with a posi pig and you're good to go.
Obviously posi's go for quite a bit more money. When hunting for a good used posi pig setup you have to know the number of splines on your axels and also make sure the pinion yoke from the old rear end matchs the splines on the "new' posi pig. My son is pretty sharp on those rear differentials as far as axel spline counts for different year application etc. Its been quite a while since I messed around with that stuff. I came to the conclusion that hot rods are a never ending money pit.