Brakes locking up

[Optimaldave]

1990 Ranger XLT, 2.9L, 4x4 stock short of cosmetics and exhaust mod

Hi, I have noticed more and more recently that my brakes seem to like to lock-up a lot...
It is very noticeable if i am doing over 80KM/hr, I basically breathe on the pedal and the rear locks up. Mainly does it after being parked for a while or after a freeway stint.

This problem is sporadic as sometimes the truck brakes normally and sometimes it locks up. Seems to be more the rear than the front...
I checked the pads and shoes not long ago and seemed to have plenty of life left and the drum looked fine. My auto adjusters are somewhat of gunky but I cleaned them up when I last rotated my tires.

I have seen the threads about the rear shoes absorbing moisture but this problem was still around through out 30+ degree days (celsius) so it makes me question that theory being my issue...

So before I throw some shoes and adjusters at it I was looking for some other advice.

My RABS light has been on since I bought the truck a year ago, but has not bugged me as I dont really care about it but could the ABS valve/pump giving me issues with brake pressure?

Thank you all for the help

 

[TRH]

See if the proportioning valve is centered, and if not, bleed appropriately to recenter it. If it's off-center and braking the rear too hard, it'll lock 'em up and turn on that lamp continously too.

 

[Optimaldave]

I had thought that they only had the pressure diff valves in the first gen rangers and the newer ones only had the RABS valve between front and rear?

I have heard the chaos of the RABS valves so weather permitting I'm going to tear it out this weekend and either bypass it or replace it...

Any other inputs and/or suggestions for removing the RABS valve?

Cheers
Dave