98 12 valve, drum brakes on rear, will not grab, the fronts will lock up when applied hard enough, I have the 90 chev wheel cylinders in and have adjusted the brakes changed fluid on all corners, what's next to check

 

Bad...Proportion valve..??? Even though I haven't heard of them going bad in any type of vehicles.....There is always the first time...

http://www.stoptech.com/technical-su...tioning-valves

 

There is some sort of load sensing porp. valve on the rear, has a lever that goes from axle to valve. As axle sinks, valve sends more fluid to rear cylinders. I think the arms rot off long before the valve fails, so you might not see that part, but look through the rear hydraulic lines to see what I'm talking about. Maybe just the arm fell off?

FWIW, the one on my truck was deleted when I bought it, though I remember seeing a linkage point on the rear end for it.

Did you do "conventional" bleeding when changing fluid? You should see a pretty good shot of fluid shoot from the bleeder once pressure is built up and the bleeder is opened.

 

So after a bit of reading it looks like I should be able to remove the porp valve and just tie in a small brake line, now will this change my braking completely and lock up the rear end? The valve doesn't work I bought the truck and noticed it wasn't hooked up and resistance when I moved it

 

Since you're able to lock up the front I assume you only have RWAL. 1998 Dodge's have it standard and it will prevent your rear tires from locking up, while your fronts lock up. Try unpluging your ABS module under the hood and see what it does. My rears never locked up until I disabled the RWAL, then they locked up before the fronts. I've the the GM rear brake cylinders as well.