1995 Chevy suburban c2500 7.4 combination valve modification.

[superchevysb]

I have read a lot of posts about the Suburbans having very poor rear brakes and mine as well. I finally pulled the proportioning valve apart and removed the spring and rubber plunger that actuated the pressure limit and it stops so much better. Also by removing the spring the valve no longer has the cushion of the spring to push against and is just bottomed out now so that greatly improved the peddle feel also. Finally getting some use out of them huge 13x3.5 Inch drum brakes! Another thing I noticed on my 1998 k1500 pickup it has the same ABS unit and combination valve except the rear section on the valve is cast solid and has no pressure limiting proportion valve so it gets full master cylinder pressure just like the one I modified does now.

 

[Spareparts]

My brakes seem to work fine, No complaints. I did need to replace the hydroboost though not long after i got the truck maybe that why?

 

[Schurkey]

I have read a lot of posts about the Suburbans having very poor rear brakes and mine as well. I finally pulled the proportioning valve apart and removed the spring and rubber plunger that actuated the pressure limit and it stops so much better. Also by removing the spring the valve no longer has the cushion of the spring to push against and is just bottomed out now so that greatly improved the peddle feel also. Finally getting some use out of them huge 13x3.5 Inch drum brakes! Another thing I noticed on my 1998 k1500 pickup it has the same ABS unit and combination valve except the rear section on the valve is cast solid and has no pressure limiting proportion valve so it gets full master cylinder pressure just like the one I modified does now.

The whole point of the proportioning valve is to prevent the rear brakes from locking before the front brakes.

The reason is that when the front brakes lock first, the vehicle will skid in a straight line. When the rear brakes lock first, the vehicle becomes uncontrollable, the ass-end will slide around whatever way it wants to.

What you did is NOT a good idea. You should have fixed whatever was wrong, instead of defeating a device designed to keep the vehicle controllable. Perhaps having functional ABS will help. Maybe...maybe not.

 

[someotherguy]

The reason is that when the front brakes lock first, the vehicle will skid in a straight line. When the rear brakes lock first, the vehicle becomes uncontrollable, the ass-end will slide around whatever way it wants to.

What, you mean the front and rear swapping ends during hard braking is an undesirable outcome?? Who knew?

Richard