Brake Promlem--Any Suggestions?

[cdrider]

believe I have a problem with the brakes on my 92 4x4. Here is what happens: Whenever the brakes are cold they work fine, but as they warm up from use the front wheels develop a shimmy(sometimes a wobble) when braking.

I have done the following: alignment, new tires, rotors turned, front wheel bearings adjusted, caliper sliders cleaned and lubed, rear brakes ajusted,all steering components verified good,metering valve OK, master cylinder and booster OK.



My suspicion is that the RWAL valve is defective, causing the front brakes to do all the work and heat up. When the front brakes get hot, they could start to grab, causing the front wheel shimmy?



What is the best way to verify the RWAL valve? Can it just be bypassed and eliminated? Anyone know how to get the error codes from the anti-lock control module--manual says ground connector, but ground it at what point or terminal?



Any comments or ideas about this problem or theory appreciated.



Thanks in advance

K

 

[Dfeland]

I have had two trucks do the same thing. Put a steering stabilizer and it will go away. Otherwise you willl end up rebuilding the front end (which it does not need) and flushing money down the toilet. They all seem to like to do it at around 100,000.

 

[ETOBICOKE]

RWAL Valve

The RWAL valve is located on the inner drivers side frame just below the master cylinder. There are two valves here, the lower one with two line connections is the RWAL. If you are planning on working on this your self I would very strongly suggest that you obtain a copy of the factory service manual.

All though you have adjusted the rear brakes I would have another look at them. The rear brakes on our trucks don't tend to adjust themselves very well and need manual adjustment to work properly. Also check for a leaky wheel cylinder or axle seal, both of these will render the rear brakes next to inoperative.

The shimmy problem you describe is does tend to happen to the 4 wheel drive trucks, you may wish to do a search in the first gen section.

Hope this helps,

Neil

 

[cdrider]

Dfeland, thanks for the suggestion--

I forgot to mention on previous post that I just installed a heavy duty stablizer and it did not solve the shimmy/wobble. I only get the shimmy after I've used the brakes a few times .

 

[Bob Beauchaine]

I had the same problem with my '93 usually 10 to 15 thousand miles after a brake job. I have replaced rotors and calipers and the results were the same - hot shimmy. I finally installed Titanium pads which helped but the biggest help was an exhaust brake. I haven't had any shimmy since the exhaust brake went on. It's something I should have done 100,000 miles ago. Hope this helps.

Happy Trails

Bob

 

[Dfeland]

I put stabilizers on both mine and it fixed a very violent wobble reffered to as the "death wobble". After that stabilizers put on brand new rotors and the shimmy as you describe went away only to return after a few thousand. I have come to the conclusion that it is possible for the actual hub to warp also. Therefore the new rotors are new until they heat up a little and then they warp again. But thus far I have not bothered to put the money into new hubs. But thats my theory. The brakes are proportioned so that the front does not do as much as the back. Otherwise the truck would start to do a 180. If you make it go away be sure and let us know. Inquiring minds want to know. Dan

 

[mark93]

Hey cdrider.



Had the same problem and it was mostly the drag link with a little too much play.



Check like this: With engine running grab the steering shaft at a point near the gearbox and turn back and forth enough to just move the pitman arm. Observe carefully the drag link ends to see if the pitman arm movement is immediately transfered to the drag link. If not replace the drag link.



The trial and error sequence for me was: 1) Rotors turned/wheel bearings adjusted to zero play 2) New tie rod ends 3) New tires 4) New drag link and slight adjustment of steering box to tighten everything up. Problem solved after drag link. Probably could have not done anything else.

 

[cdrider]

Update on my braking/shimmy problem.



First of all, thanks to everyone for all the suggestions.



The problem seems to be solved---by working on the rear brakes ! I had done nearly everything possible to the front end(see the first post on this thread), with no permanent results, so I decided to look at the rears. There was nothing obviously wrong on either side, but since it had the 2. 5" shoes, I went for the 3" setup with new 1 1/8" cylinders and all new hardware. It has been a couple of months (3,500 miles) since the rebuild and have not yet had the dreaded shimmy ! I'm convinced that the shimmy came from lazy or insufficient braking on the rears, causing the fronts to work too hard and heat up. A very interesting dynamic.

Anyone having similar problems might want to take a look at the rears.

 

[AlK]

cdrider,

Thanks for giving us an up-date on the brake problems. Will have to remember that for the future in case something similar happens to mine.

---

Al