Chevy & GMC Vans

I know this has been discussed alot. I have changed all of the normal guilty parts(calipers, pads, flex hoses , idler arm, flush). Front end is perfect now, still a pull. Garage says pressure coming out of module uneven, less pressure to left side. Has anyone had this happen before? Could it be a wheel sensor giving wrong info to the module? I hope I don't need a new module. Does this system(hydroboost) have a proportioning valve? If so, does it divide left to right as well as front to back?I have a 93 Astro awd LT. He said he pulled the abs fuse and that it also shut off the digital dash and no difference in the pulling. Any help would be greatly appreciated.

ron02032 wrote:I know this has been discussed alot. I have changed all of the normal guilty parts(calipers, pads, flex hoses , idler arm, flush). Front end is perfect now, still a pull. Garage says pressure coming out of module uneven, less pressure to left side. Has anyone had this happen before? Could it be a wheel sensor giving wrong info to the module? I hope I don't need a new module. Does this system(hydroboost) have a proportioning valve? If so, does it divide left to right as well as front to back?I have a 93 Astro awd LT. He said he pulled the abs fuse and that it also shut off the digital dash and no difference in the pulling. Any help would be greatly appreciated.

line pressures are easy to test, most garages would have a simple hydraulic pressure gauge and a variety of fittings, if not, the gauges are about $60, any hydraulic hose shop sells them and they can make you a fitting to hookup,

i would be more suspicious of control arm bushings, tie rod. the wheel sensors do no sense pressure buy movement.

the brakes have separate lines, factory right side line is one big ass long piece. if one side had more pressure, it would pull toward that side.
if you have a shop with an old school on car dynamic wheel balancer you can spin the wheels while the truck is on stands and get a sense of pressures without gauge testing them.

the hydrobooster line goes into the controller in one line for the front, the controller proportions the pressure, my understanding is that if the box fails it defaults to normal brakes, although, i have been told that, not read it in a service manual.

The problem is in the rear brakes. The right rear drum is grabbing harder than the left side. Pull the rear drums and inspect, clean and adjust as needed. You may have a leaking wheel cylinder or axle seal that has gotten on the shoes. If so get new shoes and hardware and put it back together.

LiftedAWDAstro wrote:The problem is in the rear brakes. The right rear drum is grabbing harder than the left side. Pull the rear drums and inspect, clean and adjust as needed. You may have a leaking wheel cylinder or axle seal that has gotten on the shoes. If so get new shoes and hardware and put it back together.

hmmm, not sure of that, most vehicles, if the rear brakes didn't work at all you would never know it in usual driving, they do such a small percentage of the brake work, if they overbrake on a side, usually they will lock but not pull the vehicle to the side as the back end is being dragged. this is why race cars that go very fast only have rear brakes and parachutes.

rear brakes will pull these vans to one side or the other if they aren't engaging properly basically the same way a partially seized front caliper will just not as severe. when i replaced my brakes recently it was clear my passenger side was considerably more worn then the driver side and the van pulled to the right when the brake was pressed then would straighten out after counter steering.

Thanks for the help guys. Turns out it was the abs module(don't know if that is the right name).We switched sides( coming out of abs module) left to right, right to left, then the van pulled to the left. Found one at a junk yard for $200 dollars. Now van doesn't change lanes when braking! I feel safe driving it again.

Did you try pulling the fuse to the abs unit before you switched it out? You would not have abs but the brakes would still work like a regular car. I am just asking because it could help others in the future who may have the same problem.

Just curious, if you replaced the ABS module yourself....how did you bleed the brakes? This requires the TECH2 scantool or similar device to cycle the module in order to bleed any air out of it. I would imagine pulling the module would have introduced A LOT of air into the module and lines.

I have replaced my calipers and wheel cylinders and bled the brakes like I would in a non-ABS equipped vehicle and they appear to work OK. But I have always wondered if they are working as good as they could be.

Do you have some sort of workaround for this?

I had that exact problem with my 94 and it was the rear brakes.Pulled so hard I was fighting the wheel almost a 1/3 turn.

I just bought a 1999 Safari AWD (today ). I noticed a pull to the right during my test drive of this van and another I looked at. Both vans tracked well and had well centered steering wheels. The one I didn't buy had definite front inner tread wear (camber) and some throbbing under brakes, whereas the one I bought has nice treads and no other noticeable suspension faults.

Naturally I came to ASV to research pulling to the right. This thread is the best I've found so far to describe anything similar; I will certainly inspect the rear brakes when I get her home (we haven't named her yet). But the OP states:

ron02032 wrote:I know this has been discussed a lot...

I can't bring up other threads of pulling to the right. Has it been discussed a lot because pulling to the right is common? Why right and not left? Or is that common too?

Thanks for allowing me to dig this thread from the grave; any advice is welcome.