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A little help with a rear end? (sorry that didn't sound good, but)--

August 7 2017 at 2:24 PM
Bob S.  (Login convertable)
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I've got this 9 inch that I don't know what kind of possi is in it but I do know its low on fluid. Ive so far sucked out maybe a pint (my little pump is not very good) the fuid seems clean and with a magnet I get nothing, I've never leaked anywhere. What should I fill this thing up with? , not knowing if it,s got clutches, true-trac, or locker? The fluid that Ive pumped out is clear brown- and Ive smelled worse.. Thanks for any advise.

 
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Gerry
(Login gerryproctor)
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Not much help since you may have some work ahead of you.

August 7 2017, 2:52 PM 

How do you know it is a traction differential in the first place?

There are only two differentials you can positively identify without pulling the case. Jack up the rear of the car to get the rear wheels off the ground. Turn one rear tire. An open differential in proper working order (not welded or shimmed spiders) will either rotate the opposite tire in the opposite direction or the opposite tire will remain still. With a Detroit Locker, you turn the one tire forward (the other tire will also be rotating in the same direction), then immediately reverse the tire you're turning and you should hear the clutch ratcheting as it unlocks.

If both rear tires turn in the same direction then there is some kind of traction differential but you'd have to pull it to see what guts it contains. It could be gear, or one of the clutch pack units.

Not to give you a snoot full, but "posi", an abbreviation for Posi Traction, is GM's marketing name for its traction differential.

 
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Randy
(Login 161854)
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You can also...

August 7 2017, 3:01 PM 

Pull the drain plug and look inside at the type of carrier the ring gear is attached to. Ope or Detroit will be flat where the ring gear bolts are . Equa lock , traction lock will be raised around the bolts
Randy

 
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Bob S.
(Login convertable)
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That can help- I've got use of a bore scope n/m

August 7 2017, 3:09 PM 


 
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Tom P
(Login tomposthuma)
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Re: That can help- I've got use of a bore scope n/m

August 7 2017, 5:59 PM 

You don't even need a scope unless there is no side filler plug, some have it on the rear of the housing. The "posi" bolts are smaller 5/8" hex and sit with a raised half circle around them, the 3/4" open diff bolts can be gotten at with a crescent wrench. They line up with the side filler hole so you only need a flashlight.

 
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e.philpott
(Login pooreric)
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80W90 will be fine ..nm

August 8 2017, 7:43 AM 

.

 
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Brian
(Login BrianJaspercoia)
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Fill it with modifier

August 8 2017, 10:39 AM 

Just fill it with oil that has the friction modifier in it. Lockers and Tru-Trac don't need modifier, but it doesn't hurt them if it has it.

 
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