Weird braking problem...what could it be?

[ki1022]

Ever since I purchased my 94' XJ (oct 05), i have had a strange problem with braking.

Whenever I would brake hard and hold the pedal until I stopped, as soon as I released the pedal, there would be a 'shake' from the rear of the vehicle and it would feel like something falling back into place.

After posting of Jeepforum about it a few times, I decided that my rear drums (which were in really bad shape) were sticking while braking, and popping off when I let go of the pedal.

Instead of fixing my drums, I installed a Teraflex rear-disc converstion kit about a week or two ago. Install went real smoothly and my braking power was alot better. But, the problem is not as bad, but it is still occuring. :doh:

So, what I am thinking is this: When the calipers grab the rotors, the rotational force of the rotots spinning is tilting my whole rear axle assembly slightly forward, then once I let go, it is falling into place. My driveshaft u-joints, u-bolts, and leaf spring bushings are all in pretty good shape, so Im not sure how something like this could happen...

Anyone have any ideas? This is a hard thing to diagnose since I can only recreate the problem on the road.

 

[98XJSport]

Had something like this happening after I owned my jeep for a few months, felt like I hit the brakes hard and then when I let off, it settled back, but not gently. I put in new shocks the problem was gone. I think it was the bushings being shot allowed the vehicle to shift on top of the shock movement, giving it a slight dropping back and down feel as the axle was "released" from the brake.

 

[katarn444]

So, what I am thinking is this: When the calipers grab the rotors, the rotational force of the rotots spinning is tilting my whole rear axle assembly slightly forward, then once I let go, it is falling into place. My driveshaft u-joints, u-bolts, and leaf spring bushings are all in pretty good shape, so Im not sure how something like this could happen...

Anyone have any ideas? This is a hard thing to diagnose since I can only recreate the problem on the road.

That is not a bad thought but the noise would happen when you come to a stop not when you let go of the brake. It could be something really goofy like shocks or ebrake cables. It just does not sound brake related.

K

 

[ki1022]

Had something like this happening after I owned my jeep for a few months, felt like I hit the brakes hard and then when I let off, it settled back, but not gently. I put in new shocks the problem was gone. I think it was the bushings being shot allowed the vehicle to shift on top of the shock movement, giving it a slight dropping back and down feel as the axle was "released" from the brake.

Shocks could be my problem... I think one of my rear shocks is blown and all the other ones are pretty shot.

I'm getting a small lift and new shocks in the near future, so I guess I will just deal with it until I upgrade.

Can anyone else think of anything else this could be? I'm pretty sure it IS the shocks but was just looking for extra input :sunshine:

 

[Eagle]

It's your driveshaft.

There was a TSB on the '99 WJ for this same problem. What happens is, under hard braking there's a lot of negative torque on the rear axle that wraps the leaf springs into an 'S' shape. The pinion dips down, which pulls the slip yoke farther out of the transfer case. After you stop, the splines bind up a bit, then when everything settles back to equilibrium the splines let go with a little POP as the yoke slides forward again.

Pull your rear driveshaft, grease up the slip splines with a good high-pressure grease, and see if the problem goes away or gets less severe.

 

[ki1022]

It's your driveshaft.

There was a TSB on the '99 WJ for this same problem. What happens is, under hard braking there's a lot of negative torque on the rear axle that wraps the leaf springs into an 'S' shape. The pinion dips down, which pulls the slip yoke farther out of the transfer case. After you stop, the splines bind up a bit, then when everything settles back to equilibrium the splines let go with a little POP as the yoke slides forward again.

Pull your rear driveshaft, grease up the slip splines with a good high-pressure grease, and see if the problem goes away or gets less severe.

Couldn't I put the tranny in neutral, then stop hard and see if the problem still happens? Or would that make a difference?