Did I fry my posi?

SadbutTrue · Feb 25, 2008

Was driving home a few days ago (from Rusty67's house, checking out his CPP suspension). As I'm getting off the freeway I notice a burnign smell and see smoke out behind me (wasn't sure if it was smoke or steam coming out of the exhaust pipes... it was cold out). When I get home there's a lot of smoke coming out from behind the wheels.

We initially thought the rear brakes were at fault but they appeared fine. The posi is fairly new and hasn't been abused at all... but we can't think of anythign else it could be. We're going to get under the car tonight to check... anythign else we should look for?

bnickel · Feb 25, 2008

make sure nothing is touching the exhaust and make sure the parking brake is off. i've never seen a posi unit smoke before but i would suspect the smoke would be coming from the vent tube/hose on the diff housing if that was the case, i would also suspect that if that is the case then the diff is probably dry as a bone and you need to add some fluid. check the rear axle seals and make they aren't leaking and also check the rear wheel cylinders.

mrmustangman357 · Feb 25, 2008

if there was smoke from the vent, something i.e. bearings are prolly fried

SadbutTrue · Feb 26, 2008

Alright, new information... I need stangnet's mystery solvers here...

We jacked the car up and checked the rear end's fluid. It was full, and after smelling it, the fluid did not appear burned or dirty.

Next we took off a wheel. The brakes smelled terrible and like burnt brake pads, but the pads looked alright. Also, there was some strange scoring/yielding of the material next to the lugs... on both the wheel and the drum, there were signs of fatigue and stress. The wheels' holes were elongated and both the drum and wheel had scoring markings next to them (in the direction of rotation, see pics below).

It might be worth noting that we put a rear sway bar in 2 weeks ago. You can see it in one of the pictures below. I'm not sure how a sway bar could do this, but it does seem like quite a coincidence. The posi unit is over 2 years old but has less than 2,000 miles on it. Probably considerably less, actually.

Questions:

1) What could cause stress/yielding marks on the wheel and the drum like that?
2) Does anyone have any experience with a rear sway bar installation causing any of these things (smoking from the brakes for some reason, vastly increased stress on the wheel)?
3) What does this have to do with the fact that my brakes were smoking like crazy last thursday?

Thanks a lot

PUNISHER RACING · Feb 26, 2008

did you try to back up with the e brake on ? are the slack adjusters to tight ?

SadbutTrue · Feb 26, 2008

Pics (you're looking at the passenger side rear wheel):

SadbutTrue · Feb 26, 2008

PUNISHER RACING said:
did you try to back up with the e brake on ? are the slack adjusters to tight ?

I don't think so, if anything the parking brake has been too loose recently (it hasn't been able to keep my car from moving on a hill for a while).

bnickel · Feb 26, 2008

the swaybar won't cause that unless it has serious contact with the wheel or tire and that would be really noticeable. it looks to me like you either have a dragging brake on one side or were driving around with the parking brake on.

mrmustangman357 · Feb 26, 2008

that got hot/ pull the drums and check the wheel bearings. drain the fluid and pull em out to see whats going on. either way, i would check all the stuff with that heat. If it was just one side, i might think it is brake related . .. . but if it was smoking? pull it apart to check

SadbutTrue · Feb 26, 2008

bnickel said:
the swaybar won't cause that unless it has serious contact with the wheel or tire and that would be really noticeable. it looks to me like you either have a dragging brake on one side or were driving around with the parking brake on.

There have abeen a couple cases of driving around with the parking brake accidentally.. I did it once a few months ago and i let my brother drive it around town and he did it for a while. But that was a while ago and when the rear smoked up the parking brake was not on.

Could there be something wrong with the clutches in the posi? Recently (primarily since I installed the sway bar, though they may not be connected) the rearend has been skipping some in turns... my dad thinks the posi is gripping too hard during turns and trying to force the wheels forward (against the brakes and/or the ground) during turns, acting sort of like a locker. He thinks this is what caused the scoring/stress marks on the wheels/drums and I guess what caused the smoking brakes.

Any thoughts? Need more people to chime in... Thanks to those that have

96 DOHC Cobra · Feb 27, 2008

I don't know about the smoke, but from the pictures it looks like loose lug nuts to me. You stated the rear is full of oil. If the wheel bearings were bad, there would be uneven wear on the brakes.

SadbutTrue · Feb 27, 2008

the lug nuts were pretty tight. definitely weren't moving.

does anyone agree with my dad that its probably the posi? or is it possible its something else?

mrmustangman357 · Feb 27, 2008

you need to pull the axles and center section to check things out. its a 40 minute job with air tools

mrmustangman357 · Feb 27, 2008

the posi doesnt work in a straight line, so its extremely doubtful it is what toasted your axle. skipping is a normal occurrance with a posi thats tight, but sometimes a good limited slip additive is what cures it

96 DOHC Cobra · Feb 27, 2008

What color was the smoke? What did it smell like? Did you notice any oil on the rear or the undercarriage? The smoke had to come from somewhere.

Did I fry my posi?

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