[davided]

Hi

I just picked up a 71 firebird with 10 bolt posi (at least i think). If i spin rear tires forwards they both move. If I spin backwards then forwards the rear end make a racheting type noise and the tires do not spin then it "catches" up and both tires spin.
Is this 'normal'?

Second question - when I removed rear differential had no fluid in it - the ring and pinion where nice and clean the posi case? had a little surface rust -i added fluid, what is the chances this rear end is ok?

thanks in advance for assistance.

[track73]

If you had the cover off that would have been the time to see if it is a "posi" type carrier. You can check by jacking up one side of the rear end and leaving the one tire on the ground. Put a torque wrench on a lug nut on the opposite tire and see how much torque it takes to rotate the tire. Block the car to be safe.

[MotorHead_811]

When you took the cover off did the insides look like this

[F ROCK]

or this? this is a 12 bolt, non posi. i think the factory posi will have that "s" shaped spring, like in motorhead's pic.
or it could look like the second photo, wich is another type of posi. i guess basically, if you see springs, its posi. and if it is posi, be sure to use the "limited slip" gear lube in it.

[mechanic17]

No fluid? groan--you may have bigger problems. If the car was driven AT ALL, whatever you have is probably toast. . .

[track73]

OMG I better change out my 78 suburban rear end that I forgot to fill with lube and drove for about 10 miles 15 years ago.