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I have a 78 Nova that i thought had a 273 rear end but at 300 rpms im doing 70mph. The car has a th 350 trans and a 305 sbc. Does the rear end sound like a 308 maybe? The next question is why when i do a burnout does my drivers side tire spins and not the passenger? Sometimes i even get both wheels to spin like its a posi. Will someone help me with this im going to pull the cover off one day but would like to get an idea of whats going on back there.
 

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Shop Owner And Troll Hunter
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Get the numbers off of the rear houseing, top of right side axle tube.

The engine will not run at 300 rpm....3000?

Jack the car up and turn the rear wheels, if they both go the same way, it's a posy, if not then it's a single track.

Troy
 

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Shop Owner And Troll Hunter
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They are stamped deep into the rear housing, the exhaust can't wear them off.

Troy
 

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There is an old trick i found in here before about jacking up one tire and turning the driveshaft. Mark the tire and see how many times it goes around. I dont remember what the exact numbers are but i did this on my 79 nova and according to it i had 3.08 gears. I too am at about 3000 rpms at 70mphs so i guess it is possible. What i want to know is are these the stock gears on a car like this?
 

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Put the car in neutral, chock the front wheels, disengage the parking brake, & jack up one back tire. Will it turn? If so, it's probably an open differential. If not, it may be a limited-slip (posi).

If it's an open diff, turn the tire TWO full turns, and at the same time count the revolutions of the drive shaft. That's your ratio. I find it easier to turn the tire until the valve stem is down & there's a flat end of the U-joint up before I start counting. Then turn the tire twice (slowly) by feel, while watching the U-joint. If the driveshaft turns 2-3/4 turns, it's a 2.73. If it turns about 3-1/8 turns, it's a 3.08. Etc.

If it's a posi, you need to jack up both back tires, & only turn them ONE full turn when you count driveshaft revs.

Stock gears on those cars were generally 2.41 - 3.08, depending on engine & transmission installed at the factory.
 
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