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Discussion Starter #1
My understanding of positrac rear diffs is that when the right wheel slips you get traction to the left. with a standard diff you get power only to the right. since i'm not sure what i've got, and i noticed something yesterday, i'm hoping for a bit of an explanation.

I threw the car into reverse while parked on some damp grass. Wheels slipped and when i pulled away i noticed two bare spots. will a standard differential send power to both wheels in reverse, or do i have a posi differential?
 

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Former Super Moderator
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It is possable to get both spinning with an open rear end, but it's rare and conditions would need to be just right. To be sure if you have an open or a posi, put one tire in the gravel/ice and one tire on the pavement, gun the throttle, if just the one tire spins it's an open, if both spin, it's a posi.
 

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with the standard open diff the wheel that spins is the one with the least resistance. the right tire spins most often because the rotation of the engine is trying to lift it up while pressing the left one down. if traction is equal either one or both can spin.
 

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67 Basket Case Restorer
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Since the gravel/blacktop scenario gives you an excuse to spin the tires, you could just do a power brake too....:lol:
Of course that is harder on driveline components and if it is an open diff and only 1 wheel spins, you don't want to do that for long. The spider gears inside the carrier have no bearings to carry the load and with only 1 axle/side bearing spinning, it can over heat and cause damage to the gears and carrier. It's the Newtonian effect of a non-compressible fluid being forced out of the contact stress area due to non-forced circulatory lubrication.....:D
 

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Just jack up the rear end and spin the tires by hand.

non-posi should turn the opposite from each other.





jmo
 

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67 Basket Case Restorer
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Just jack up the rear end and spin the tires by hand.
Phffffttttt........that's no fun, Bobby. He wants to mash the throttle, hopefully hear a tire howl and see smoke......:rofl:
 

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Discussion Starter #8
Since the gravel/blacktop scenario gives you an excuse to spin the tires, you could just do a power brake too....:lol:
Of course that is harder on driveline components and if it is an open diff and only 1 wheel spins, you don't want to do that for long. The spider gears inside the carrier have no bearings to carry the load and with only 1 axle/side bearing spinning, it can over heat and cause damage to the gears and carrier. It's the Newtonian effect of a non-compressible fluid being forced out of the contact stress area due to non-forced circulatory lubrication.....:D

now THAT'S an answer I can understand :lol:
 

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67 Basket Case Restorer
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now THAT'S an answer I can understand :lol:
Thank you............
Thank you............
Thank you very muuuuuuuuuuuch.......:D
 

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Still waiting to hear about what diff you have. O'yeah, you're probably at work. Say, who's that looking over your shoulder??!!:eek::rofl:
 

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Discussion Starter #12
Still waiting to hear about what diff you have. O'yeah, you're probably at work. Say, who's that looking over your shoulder??!!:eek::rofl:
monitor faces the window...so whoever is on the 7th floor of the building next to me peeping in with a set of binoculars. Hopefully she's a nicely put together young lady who finds my shoulders attractive and not any number of other negative possibilities.
 
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