Possible Posi Problems?

68 wildcat

Active member
Hi all,
Had the diff bearings and axle shaft bearings and seals done last year on my 68 Wildcat with a 3.07 posi trailer tow package. My hearing is now pretty bad and I only realized the diff bearings were going because I had every piece of the interior out except the driver's seat and dash and could now hear it without the jute/carpeting in.
Maybe 70 miles put on the car since last year and it now does a strange thing during a low speed turn. There is a sensation of the rear of the car swaying slightly from side to side as if one rear wheel is locking up slightly. Brakes and any rubber parts associated with the brakes replaced, spring kits,fluid flushed and replaced. Handbrake cables are free and return properly, so I'm ruling out brakes. All rear suspension bushings are old, but show no movement when tested with a large screwdriver. Everything was o.k. I believe, before the diff work, but I can't prove it. Cost around $800. parts and labour as he had to open several kits to get all the correct bearings for the crown and pinion, or so he said. Also, the first time i came to pick it up, I (thankfully) had a look underneath to find a 3 inch puddle of diff oil coming out of the "new" pinion seal. Car was ready the next day and hasn't leaked since. Since being 70 miles and 9 months . I'm hesitant to go back. opinions please.

Gary, it sound like the posi unit is not working correctly. If you lift the rear off the ground, the tires should spin in the same direction when spinning one. If not the posi unit probably needs a rebuild. You might want to check for the one wheel peel. Also, check the fluid level before taking it to someone. Maybe it was not refilled correctly. Do you have differential specialists where you are? That's where I would take it.

68 wildcat

Active member
The place I took it to was a trans /diff specialist that came highly recommended so I guess I could go back, but they didn't impress me, but in general, diff shops around Montreal only seem to do commercial vehicles and rarely cars.


Active member
When new fluid was added, did you use the Posi additive?

It just sounds like the Posi is not releasing on turns, it is sticking and resisting allowing both wheels to turn at different speeds the way they need to in a turn. The Posi additive eases that, that's what it is for. My rear did that when the Eaton Posi was new.
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Check your fluid level and add the Posi additive. Then drive the car in a parking lot area in a slow left tight turn 10 times to work the additive in to the clutches then do the same turn to the right for 10 times. You will hear popping and clicking that is normal but should clear up after a drive. This also needs to be done if your car sets for long time (thru winter for example) to work the additive in to the clutches. HTH