Symptoms: Regular driving no problems. Brake pedal seems kinda soft and truck pulls to the left. Emergency braking situations mean ABS sometimes works other times just turns on both the rear antilock light and the brake light. Then the pedal gets nice and firm and the truck doesn't pull at all and stops better all around but does lock-up. Think maybe its the combination of a marginal master cynlider and maybe a sticky caliper. Can anyone explain how the rear ABS works in 88. i know the sensor is off the rear diff, but how does it modulate the braking? bypass valve? Can I easily disable it and improve the pedal feel? Throw me a bone.

Randy
88 f-150 122K miles 302 M5OD 3.55 LS MSD Blaster coil.

 

Randy , Id have a look at all the brakes , pay particular attention to the rear brake cylinders . If they are leaking or not functioning properly then its possible to have pressure conflicts in the whole system resulting in erratic brake action , pulling , uneven stops etc . What I have seen is metal particles on the rear abs sensor in the diff causing the abs light to turn on . Also if the Brake light is coming on this indicates a low brake fluid condition in the master cylinder . Check all the brake linings for wear . Although the rear brake shoes dont contribute a lot to the overall braking , they will cause problems if they arent doing their share of the braking work .

 

Thanks for the help.

I know about the metal particle problem, I've been dealing with that since my rear carrier was destroyed. I am sick of cleaning off the metal particles. I checked the rear brakes and they are good, no leaks and i changed the shoes/springs/etc last February. From the wear pattern on the front rotors, I am pretty sure the drivers side caliper is stuck (it doesn't rub much of the rotor).

But what I am really worried about is the fact that before the ABS light comes on the pedal is soft and after it comes on the pedal gets hard. Why does it do that?

Thanks again.
Randy

 

Its possible the RABS module , located down on the frame , is the trouble ? Check the calipers & their hoses . What I have done with the aid of a helper is have them apply the brakes while you observe whether the caliper is clamping & releasing .