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Old 05-10-2011, 06:11 PM   #1
'70GMCStep
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Positrac rear end

Have a little concern.

I think my positrac clutches on my rear end are going bad on my '65. It grinds when going around corners especially if I accelerate even a bit, and now it is getting worse. Will or did this do any harm to my 700 r-4 and the drive line while I was driving it for...quite a while until noticing it getting bad today?

Thanks guys.

'70GMCStep

1970 GMC Stepside
1965 Chevy LWB
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Old 05-10-2011, 09:12 PM   #2
Alan's Classic
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Re: Positrac rear end

When was the last time you changed the fluid and did you put any posi additive in it?
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Old 05-10-2011, 11:06 PM   #3
'70GMCStep
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Re: Positrac rear end

About two years ago and it was added to the rear end.


'70GMCStep

'70 GMC Stepside
'65 Chevy C-10
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Old 05-11-2011, 01:32 AM   #4
Captainfab
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Re: Positrac rear end

If indeed your clutches are going out in your posi, that isn't going to hurt your trans or driveshaft any. Have you checked your U-joints?
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Old 05-11-2011, 06:01 PM   #5
wildearp
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Re: Positrac rear end

Time to get a true-trac.
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Old 05-11-2011, 06:26 PM   #6
awbrown
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Re: Positrac rear end

I think all posi's make noise at some time or another , it seems to me that the posi lubes are not all the same , friction modifiers differ from factory lubes to aftermarket lubes ... go to the dealer and get the GM stuff and if one doenst do it get another ......as long as it burns both tires dont care if it makes noise...mine makes noise and I just ignore it ....
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Old 05-11-2011, 06:35 PM   #7
lakeroadster
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Re: Positrac rear end

It definately puts some high loading into the rear suspension components and can overstress bushings, I learned this the hard way on my coil over shock suspended Model A that runs a 12 bolt posi.

Before I put the posi-additive in it the rear axle the non-slipping posi ate the bushings out of the shocks where they attached to the rear axle.

I put enough additive in it such that it didn't chatter going around corners, installed some new bushings in the shocks and haven't had any problems since.

Might be worth looking at your track bar bushings and the trailing arm bushings. Better safe than sorry.

Happy trails!

John

PS: yes it does still leave two nice burnout tracks, so the posi clutches are grabbing during hard launches.

Last edited by lakeroadster; 05-11-2011 at 06:39 PM.
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