68 electra rear differential

[Guest]

How can I tell if it is regular or posi-trac?<BR>Need to change the fluid and I want to use the right stuff! Thanks!<BR>Large Marge<BR>68 225 conv.

[Guest]

According to my '68 Buick Service Manual, that type of P/Trac unit uses springs to keep the clutches locked until they unlock to go around corners and such. It will take 4 1/4 pints of grease to fill it up, according to the specs in the manual.<P>Unlike prior times when there was a particular GM part number PosiTraction only grease, all of the rear axle lubes are now universal, even the current GM lube PN 1052271. GM still sells the little bottle of PosiTraction additive (1052358, I believe) to go with the new grease to keep the clutches from chattering or popping on corners.<P>With both rear wheels off of the ground, if you turn one wheel, both should turn the same direction and speed due to the preload springs keeping the clutches locked up. If you similarly turn one wheel the other way quickly, the other wheel should do likewise. When the P/Trac vehicles were produced, there usually was a red plastic tag around the rear axle plug where you checked the grease level, but that could have been long gone by now.<P>On a non-P/Trac car, typically one wheel will spin independently of the other one, or spin the opposite direction from the one you're spinning. Sometimes, if you can get the spider gears not to move, you can spin them both the same direction, but that takes some doing sometimes with nothing to lock the two axle shafts together.<P>Enjoy!<BR>NTX5467

[NTX5467]

Not sure why I came up as "unregistered" above, but it's me.<P>NTX5467