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how to check for posi?

paddlerdan

NAXJA Forum User
Location
maine
Hi gang,

I'm an old So Cal off roader that needs some fairly elementary info on Identifying a posi/locker dif. vs. an open rear?
Say I am buying a differential from wherever. On or off the Jeep. Is there a way to check for a posi diff without pulling the cover?
By the way, no tag on cover.
I can tell what I have when the rear end breaks loose off-road, I cant do that all the time, are there any other tricks I can do?
 
paddlerdan said:
Hi gang,

I'm an old So Cal off roader that needs some fairly elementary info on Identifying a posi/locker dif. vs. an open rear?
Say I am buying a differential from wherever. On or off the Jeep. Is there a way to check for a posi diff without pulling the cover?
By the way, no tag on cover.
I can tell what I have when the rear end breaks loose off-road, I cant do that all the time, are there any other tricks I can do?


jack up the rear end, spin one tire, if the both go in the same direction there is some type of lsd/locker, if the wheels go in opposite directions it is open.
 
Either have the trans in Gear (Manual) or Park (Automatic), and the wheel should NOT be able to turn by hand. If the other wheel spins in the oppossite direction, its an open diff.

OR

Have someone try to turn the wheel in opposite direction.

With no resistance, I have seen both wheels spin in the same direction with an Open Differential, I'm guessing there was probably some gunk or wear creating a little friction to do that. Rare with RWD/4WD axles, spinning one wheel by hand, but not that uncommon with FWD transaxles. A 2nd person at the other wheel either giving some resistance or spinning in the opposite direction will easily overcome that.

With a good LSD, 2 people at opposite wheels can't break the wheel free and spin them in opposite directions (well, at least NOT without incredible effort or tools), the resistance is too great.
 
That's exactly what I am after!
So another way to put it is say with a junkyard axle, with the pinion held fast with posi: BOTH axles will stay locked as well... right? And with an open diff one or both axles will spin.
Do I have it?
 
Its now so simple. With any street-drive-able differential if you lock the pinion (tranny in park/gear) both wheels will turn in oppiste direction if you turn them slowly. An open diff you can spin as fast as you like, while a limited slip will lock up if you get it going fast enough. (May be hard to do if you have an axle w/ no wheels.)
 
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