What is the linkage on my rear axle

[Anthony84]

On the rear axle of my 1986 3/4 ton suburban there is a linkage thatbolts to the cover an connects to a block that the fuel lines run into. From the way it looks to me if the axle rolls back like it would on a hard take off the linkage pulls down and looks like it would close off something in the block

 

[Blue85]

Many of those trucks had a load-adjusting brake proportioning valve. The more weight you put in the back, the more the springs sag and the greater pressue delivered to the rear brakes.

 

[sweetk30]

fresh topic here http://coloradok5.com/forums/showthread.php?t=294945