Yesterday it was raining and i had to get on my Brakes kind of hard not slamming and the lock up and start sliding my truck does have hab dont it? or do you think the porportioning valve could be bad?

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1999 2 wd4 cyl2.5l5 spd135k
MODS:5% tint all around Night Shades (Extra Dark)Corners Thrid BrakeTails Air silence removed 2006 Mirrors Flowmaster Super 44 (Weld on & Turn down)
35W 5000K Hids