brake shudder/vibration

[oldchevy]

I guess it is break season.

91 c1500 4.3L 175,500 mi.

I put new pads and shoes on, but could not mill the rotors or drums due to thier thinness. I did not have the money to replace them either.

The problem was their before and still since I put new pads and shoes on.

The problem is that there is a lot of vibration when I come to a stop and continues even when I am at a total stop. The vibration stops once I release the break and then step back down on it. It vibrates the entire vehicle.

Any ideas? Is this a master cylinder or combination valve. The combo valve is only a couple years old. Or do you think it's just the old and thin rotors and drums being warpped?

[2000CAYukon]

It is kind of hard for a warped rotor/out of round drum to vibrate your truck after coming to a complete stop. I am not saying that the rotors/drums are not part of your problem; however, they can not make your truck vibrate after a stop.

To me, this sounds more like the RWAL (rear wheel anti lock) is kicking in.

You could probably disconnect the RWAL controller (mounted to the master cylinder) to see if that is causing your problem or not. Disconnecting will make the brake light come on but will disable RWAL.

//2000CAYukon

[777stickman]

The CAYukon's got a good point. One thing that comes to my feeble mind is the drive line/tranny binding up at a stop?? Try putting the tranny in neutral next time you start to do a regular "vibration induced" stop........Steve

[oldchevy]

well, i tried shifting into neutral at a stop and that did help, no vibration. I just had the trans. serviced and I have new engine and trans. mounts and u-joints. What would be binding and how in that area? Also, there was no issues when the trans and u-joint was service..at least they did not mention anything.

Also, I do have sever wear in my ball joints, tie rod bushings and control arms. Is it possible that due to that the vibration is just very noticible now.

Also, is it possible that the vibration goes away in neutral becuase it's a change in engine speed and thus less vibration. Any possibility that in drive that it creates a specific pitch that is just enough to create more vibration.

thanks for the input all.

[777stickman]

I doubt it's an engine problem, but?? Sounds more like a torque converter/tranny thing. Wish I could more help.........Steve

[bigj-dog]

I'd lean towards the torque converter not completely disengaging. Check your fluid, maybe just change it for kicks and inspect whatever is in the bottom of the pan.

[MyTOY]

I had a similar prob. when at a stop in drive. It was my muffler sagging
just enough to vibrate on crossmember. It would go away if I put it in N.
The engine smoothed out in nuetral enough to stop it. Just thought is was
worth mentioning cause it had me worried because it was right below me
I thought trans.

[oldchevy]

thanks for the insight guys. I just had the tranny serviced with both a full fluid and filter replacement and they did the vacume fluid replacement by mistake the first time so I know every drop of fluid is new and there was nothing in the pan. I actually asked them to inspect the torq converter as welll and all was fine.

Now, I have tested it in a few manners. The problem goes away after I put it in neutral at a stop and it does not happen if i shift into neutral before I stop. It's very strange. I to think it has something to do with the tranny, but does anyone know a way I could test it or know for sure if the torque converter is not disengaging?

I also took it to a drive train specialist and they could not figure it out as well. So I am stummped.

Either way thanks for all of the ideas.

g

[777stickman]

I'm really leaning towards the converter clutch not disengaging also. What I don't know is if your '91 has the capability to send that info to a high end scan tool. If it does take them for a drive (you drive 'cause you know what's happening) while they monitor the scanner for the converter clutch info.

Another thing to try is starts and stops under 40 mph leaving it in gear. Most converters will lock up above 40 mph in drive.

[Mr. Smith]

Originally Posted by oldchevy

I guess it is break season.

91 c1500 4.3L 175,500 mi.

I put new pads and shoes on, but could not mill the rotors or drums due to thier thinness. I did not have the money to replace them either.

The problem was their before and still since I put new pads and shoes on.

The problem is that there is a lot of vibration when I come to a stop and continues even when I am at a total stop. The vibration stops once I release the break and then step back down on it. It vibrates the entire vehicle.

Any ideas? Is this a master cylinder or combination valve. The combo valve is only a couple years old. Or do you think it's just the old and thin rotors and drums being warpped?

You answered your own question. Change the rotors.