Rear brakes grab before front...any ideas?

[6SENSE]

The rear brakes seem to be getting more pressure quicker than the front when I press on the brake pedal. I notice more brake dust and heat comes from the drivers side wheel so it may just be that side that has the problem but Im not sure. When I have to make a sharp stop if I put pressure on the brake pedal a little too quickly the rear will lock up and kick out to I think the left/drivers side. I dont lose control because the fronts are working normal but its like Im just dragging the rear of the car when this happens and you hear the screech and see smoke from the rear tires.
I also recall a few times putting the car in drive and it didnt want to move on its own. I had to give it some gas to go. It was apparent that the rear brakes were "sticking" (like I said possibly just the drivers side). This happened to me at the track while I was in the staging lanes. Dont know how it affected the car when I ran.
Heres some info on the cars brakes: Stock hydroboost setup, normal setup up on front wheels, s10 wheel cylinders on rear with stock type shoes (not softer ones). s10 wheel cylinders have been on for 5 years or so with no issues. Problems just started this year. I installed Summit linelock (same as Hurst roll control) this year down off the proportioning valve per the instructions.

ANY IDEAS??

 

[kh440]

First thought is the mechanical self-adjusters/linkage. What could be happening is the shoes keep adjusting out against the drum. Only other thought is the metering valve malfunctioning. First thing would be clean and adjust the rear shoes and maybe get new adjuster wheels just in case. They aren't too expensive and most parts houses have or can get them.

 

[GN1587]

Rear brakes either way out of adjustment or shoes are soaked with brake fluid from leaking wheel cylinder or gear lube from leaking axle seal.

 

[Rickracer]

Ditto

I would bet on wet shoes.

 

[bkoons]

I had the exact symptoms after a suspension/steering rebuild. Didn't have any lines off or anything but pulled the calipers from the spindles. Afterwards, if I was going slow thru a parking lot or out the driveway the rears would lock up and grab under light pedal. The powermaster was was humming (pumping?) quit a bit I noticed also. Pulled the reservoir cover and the long chamber on the RH side was pretty much empty. Added some fluid there and the problem disapeared. Cant explain why, but that fixed the problem for me.