Hello,

I have a 1967 Delmont 88 with a O type differential (~2.90 or so). If the car is in park, with both rear wheels off of the ground, one wheel spins the opposite of the other wheel when turned by hand (similar to an open rear). However, if I engaged the high stall on the slip pitch converter and spin the wheels (with nice smoke from the tires [please see also post in the trans forum for second gear now slips]) it will consistently lay a trail of double tire tracks--like a posi. Could this be a posi--even though the wheels turn opposite directions when turned by hand as mentioned above?

There is a tag on the rear saying to use limited slip lube only but I have never removed the cover.

Most of my experience has been Ford or Chevy posi's and I'm a little confused....

Any comments would be greatly appreciated.

Thanks,
Chris

 

Crack open the cover & take a look. If nothing else, it's a good chance to change the gear oil.

 

Sounds like a limited slip rear to me. That little aluminum tag is a dead give-away...and the 2 black lines in the street

 

Thanks! The gear oil looks new and the black lines on the street are good enough for me!

I'm probably going to keep the ~2.90 gears since it meets the criteria for a cool custom hot rod (will smoke both tires almost indefinitely) and cruises nicely on the interstate.

 

The fact that you can spin the wheels in opposite directions tells me that the clutches in the differential are worn. I doubt this is an Eaton centrifugal style anti-spin like the one in my truck. In that case, there's no locking until one side starts spinning above a certain RPM differential, then the locking feature kicks in. Not the smoothest design in the world.

 

If you spin the wheels,with the car in neutral,they should spin the same direction,but it does sound like the posi is not real tight. That is not surprising,as they did not assemble those with any aggressiveness at all.

 

Thanks! As long as it hooks up with both wheels and it's quiet I'm happy. There won't be any drag racing--just low speed shenanigans.

 

Too loose is NOT good either. It would just take a little bit of time and about .010 shim on each side of the clutch pack to get it back in shape again. Just remember if you blow the spider from too loose of clutches THERE ARE NO AFTERMARKET ONES and these rears posis are SUPER hard to find anymore.

Jim
J D

 

Thanks!