I have a Chrysler 8.25 in my 95 Dakota What is the propper gear oil. cant find my manual. also, with the rear end off the ground, tires not touching. trans in park. should the wheels turn. I beleive so. but want to be sure. one fwd one rev. drive shaft not moving. thanks. I do remember parking onece and one wheel was on ice and the truck rolled. The other was on more solid traction.. sanded snow.

 

i cant answer about the gear oil but with both wheels off the ground your one tire should go fwd and the other in reverse. thats normal you have a limited slip differental, i learned the hard way when my truck tried to roll down the driveway when i just jacked up one side in the rear.

 

Thats wrong. With limited slip, both wheels will go forward. With an open differential, the wheels will spin differant directions.
The proper gear oil is 80W-90. I believe another common one is 75W-140. If you have a limited-slip differential, make sure you add a container of friction modifier. You can buy this at the dealership, and its like $8/bottle (the bottle is like 6 ounces or something). Failure to use this on a LSD can cause clutch chatter and possibly destroy your differential!!
The rear axle (8.25) will take about 2 quarts, and the front (if 4x4) will take about 1.5 quarts.
(If you have 4x4, a little FYI, the transfer case takes just over a quart of ATF+3 or ATF+4 transmission fluid).

 

Another thing that i put in my rearend when i serviced it was Lucas haevy duty oil stabilizer. I dont have a limited slip and it was holwling, but that has been 46,000 miles of torture ago!!!, and it does fine still.

 

I run Mobil Synthetic 75-140 in the front and rear. This was reccomended for heavy duty use such as towing or just plain beating the snot out of your truck. Synthetic lasts longer, and moves alot better in the Minnesota freezing *** cold than conventional. I have also run synthetic Dex III in my t-case. Hard to find that stuff though, not very popular I guess. If you are looking for fuel mileage, every last bitof friction and heat that you can get rid of is going to help. Just my 2.5 cents(inflation)