68 positraction
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Instructor
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From: Demotte In
68 positraction
My 68 has AN positraction - the question is was that limited slip and with 1 rear tire jacked up off the ground should I be able to ture the tire a 1/2 turn with the other tire still sitting on the ground?
Thanks
Ed
Thanks
Ed
Race Director
Joined: Dec 1999
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From: Forked River NJ
If it is a posi and it is still in good shape no you cannot turn it, maybe with a lot of force you can. They can be worn out and the clutch packs shot allowing this so it may be a posi just a worn out posi.
Team Owner
Joined: Jan 2006
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From: Crossville TN
It is also possible that the box in your car does not have the Positraction option (G81). Positraction, while very popular and almost every Corvette was ordered with it, was still an option. The 'standard' rear axle was not a Positraction unit until 1976 or 1977.
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Instructor
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From: Demotte In
Yes the car has positraction the stamp on the rear end is AN= 3.55 positraction.
The rear tire really only turned between a 1/8 and 1/4 turn then it seamed to lock in place and will not turn now. I had one of the half shafts replaced a few months ago and maybe the shafts were not lined up properly like they are suppose to be at 90* off from
each other.
I would guess with 100k miles that the differential is becomming a bit tempermental.
The rear tire really only turned between a 1/8 and 1/4 turn then it seamed to lock in place and will not turn now. I had one of the half shafts replaced a few months ago and maybe the shafts were not lined up properly like they are suppose to be at 90* off from
each other.
I would guess with 100k miles that the differential is becomming a bit tempermental.
Race Director
Joined: Jul 2001
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The rear tire really only turned between a 1/8 and 1/4 turn then it seamed to lock in place and will not turn now. I had one of the half shafts replaced a few months ago and maybe the shafts were not lined up properly like they are suppose to be at 90* off from
each other.
I would guess with 100k miles that the differential is becomming a bit tempermental.
each other.
I would guess with 100k miles that the differential is becomming a bit tempermental.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Shaft alignmant has nothing to do with it. The alignment is always changing when going around a corner. Sounds like you have posi issues. Might be time for it to come out and be rebuilt. With 100K it is definitly worn out.
Instructor
Joined: Jun 2011
Posts: 183
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From: Litchfield CT
posi
Yes the car has positraction the stamp on the rear end is AN= 3.55 positraction.
The rear tire really only turned between a 1/8 and 1/4 turn then it seamed to lock in place and will not turn now. I had one of the half shafts replaced a few months ago and maybe the shafts were not lined up properly like they are suppose to be at 90* off from
each other.
I would guess with 100k miles that the differential is becomming a bit tempermental.
The rear tire really only turned between a 1/8 and 1/4 turn then it seamed to lock in place and will not turn now. I had one of the half shafts replaced a few months ago and maybe the shafts were not lined up properly like they are suppose to be at 90* off from
each other.
I would guess with 100k miles that the differential is becomming a bit tempermental.
The, on a nice clean road surface, do a little burnout. Not the John Force type, just a little one to verify you lay down two good stripes. I expect you will see a good pair.
Also, mileage has nothing to do if the positraction unit is worn out. Poor maintenance and abuse do.
Change the lube.
Last edited by 68sbcoupe; Jun 17, 2011 at 09:10 PM. Reason: oops. Spelling error
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Race Director
Joined: Dec 1999
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From: Forked River NJ
I'll disagree with you on this slightly. Mileage has everything to do with the posi being worn. The only time the clutches are slipping is when going around a turn. A burnout will not have the clutches moving at all providing you are in a straight line. Now doing donuts in a parking lot and burning out around corners yes that will wear them out. Changing fluid on a smoked set of clutches will not briing them back. The only way to really test this is with a torque wrench and test the breakaway torque required to turn one wheel while the other remains stationary. You are right though most of the posis even worn will do fine on a mildly driven car. They will provide 2 nice streaks on the pavement, unless the posi is totally shot.
Le Mans Master
Joined: Sep 2004
Posts: 5,116
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From: Livonia MI
You probably have posi, but with that kind of age/milage, good idea to pull the diff cover, drain and inspect things. I've seen spider gears weld themselves to pinion shafts, shear the bolt and start wearing against the housing. Posi clutch pack wear is common, and probably worth replacing. Careful with friction modifier additives, while usually quiet things around turns, can really cut down on posi clutch lock up action when you're wanting it.
Advanced
Joined: Jan 2002
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From: Stillman Valey Illinois
I'll disagree with you on this slightly. Mileage has everything to do with the posi being worn. The only time the clutches are slipping is when going around a turn. A burnout will not have the clutches moving at all providing you are in a straight line. Now doing donuts in a parking lot and burning out around corners yes that will wear them out. Changing fluid on a smoked set of clutches will not briing them back. The only way to really test this is with a torque wrench and test the breakaway torque required to turn one wheel while the other remains stationary. You are right though most of the posis even worn will do fine on a mildly driven car. They will provide 2 nice streaks on the pavement, unless the posi is totally shot.
