Disabling Brake Proportioning Valve

[Midnite]

I'd like to see how the braking is on my truck with the proportioning valve disabled/bypassed. What would be the best way to do this, but still allow me to re-enable it if I don't like the braking characteristics with it disabled?



Thanks,

Mike

 

[Midnite]

Hmmm... I found my service manual, and despite what I remember reading here there doesn't appear to be a proportioning valve in the system--the closest thing seems to be the Rear Wheel Anti Lock (RWAL) valve by the rear axle.



Is the proportioning valve a 2nd gen thing maybe?



The whole reason I had wanted to do this was because I wanted to try to increase rear braking power. Yes, yes, I know about going from 2. 5" shoes to 3" shoes, and going with larger wheel cylinders. However, my rear brakes are barely even being used now--this winter on slick streets my front wheels would lock up if I just LOOKED at the brake pedal; on the other hand, on that same slick street I'd have to STAND as hard as I could on the pedal to get the rears to even begin to lock up.



What I ended up doing was throwing it into 4wd almost every time I had to stop, and that gets real hairy if it's a panic stop. According to the service manual, engaging 4wd disables RWAL, so I'm wondering if that's where my increased braking is coming from.



From looking at the manual, it looks like I can disable the RWAL valve by disconnecting the harness from the controller box under the passenger side of the dash, or also from the valve itself by the rear axle.



What kind of problems might I run into if I unplugged at either of these locations?



Thanks,

Mike

 

[cummins2go]

Hi Mike the proportioning valve should be located on the top of the drivers side frame rail just under the master cylinder. I have had alot of problems with the abs and disconnected it at the brain behind the glove box when I did it also disconnected my brake lights from working. I think if you dissconnect at the rear end you might have better luck

Darrin

 

[Midnite]

Originally posted by cummins2go

when I did it also disconnected my brake lights from working. I think if you dissconnect at the rear end you might have better luck

Oh how fun.



Thanks for the tip--I'll play with it and see. I suppose it'd be just my luck that it'd kill my brake lights...



Thanks,

Mike

 

[TShikoski]

RABS valve

Hi Mike,

Had a problem like you describe and though this does not come recommended by anyone including myself, I disassembled the ABS valve by removing the piston. Things seem to work "better" for me now. Also did'nt screw up the lights as stated in the previous posts. Remember that to tamper with this device is to risk rendering your brakes unusable. Do so at your own risk.

 

[Midnite]

Ski--thanks for the head's up.



Actually, after spending a siginificant amount of time going over my service manual, I think we're all confusing two different things:



1. RWAL Valve

2. Combination Valve



cummins2go refers to the combination valve when he mentions it being on the drivers' side frame rail, just under the master cylinder. The RWAL valve is also on the drivers' side frame rail, but back by the rear axle. I disabled my RWAL by unplugging the harness from the RWAL ECM (black box under the dash behind the glove box, just below the blower motor resistors). I noticed no change at all in braking characteristics, and my brake lights continued to function fine. I was expecting the brake warning light on the dash to come on, but it just flashed the code for "open wiring to ECM" or something like that.



I'm going to reconnect the RWAL computer module and test again next fall when the streets start to ice up, and then see what effect it has.



I'm sure I started the confusion in my initial post when I asked about the "proportioning valve"--I'd seen references to that in threads here as well as in a TDR magazine article (one of Bill Swails'). However, there is no mention of ANYTHING called the "proportioning valve" in the service manual. Could this be another name for the combination valve?



C'mon--where are the brake system gurus out there?



Thanks,

Mike

 

[bvanetten]

"C'mon--where are the brake system gurus out there? "



Yeah! My brakes suck also.



Bruce