Brake problem on 1993 D350 dually
 

Seems like I have no rear brakes. I put new brakes on the rear because they were shot. Went for a test drive and just the front brakes will slide and the rear brakes will not slide at all could this be a bad vac pump.

i have a 92 dually and it has rear anti-locks it dont skid rears either.

as mentioned, the rear ABS willnot let teh rears lock up...
if yo dont think this is it, describe what you did and what its doing in more detail..

When I really noticed the brakes I was pulling a small trailer the trailer had no brakes and I had to stop fast and I stomped on the brakes nothing happened it was like I had no brakes so I let off then stomped them again and the front brakes skidded for about ten feet and then they faided away. The pedal did not fall to the floor it was more like a rock and nothing there.

Possibly a bad master cylinder? I just had a rear brake problem on my truck. Fixed it by bleeding some air from each rear drum. Do the cheap fixes first rather than spending $24 on a rebuilt master cylinder that I probably didn't need.

Thank you Ill give that a shot and report back

Anytime you do brake work, it is a good idea to flush the old fluid from the system and get fresh fluid in there. I do mine every 18-24mo, just because brake fluid and a 4' section of vinyl hose are cheaper and easier than replacing stuff.

That said, how tight did you adjust your rear brakes? They need to be tighter than on a half ton or a car. My g/f's boss, who runs one of the better shops in Cape Girardeau (general consensus) told me to tighten them til they'll go no more. This gets the shoes against the drum all the way around. Then you back them off about 5-8 strokes of the screwdriver (2-3clicks/ stroke). Make sure they turn with equal resistance on each side. You should have considerable drag all the way around. IT helped mine out a whole bunch. It gets a bit messy, but I find I can get a more even adjustment if I pull my axle tubes out a bit, then adjust. BE SURE TO CHOCK THE FRONT WHEELS IF YOU DO THIS!!!![nonono][nonono]

Bypassing the RWAL valve is an option to increase rear brake bias, but you lose your anti-lock capabilities. Whether you need it is up to you. I learned to drive on early 70s vehicles, so I prefer to be without it.

most- check your vacuum. If your pedal got hard, it is a vacuum issue (or you have a blockage somewhere). My pump pulls 22-25inHg. AT least I think it's inHG- it's whatever the scale is on the Redline vacuum gauge I have from a bygone vac-over-hydraulic brake system on a truck a long time ago. Do your heater controls move and change?

A bad booster wont affect braking (other than an extremely hard pedal), and a master cylinder wont affect your booster. I cant count how may people have told me to check my booster when the pedal falls to the floor. They are two different, sealed off systems, how can one affect the other?

Daniel