Can't lock up brakes
 

I can stop fine in normal driving conditions, I can stop pretty quick but, I can't lock the brakes up no matter how hard I try.

In fact is seems the faster the pedal is pressed the more it resistance change.

Something else I've noticed is in the winter if driving on ice. If I brake hard the front wheels will lock up but, the rear will keep pushing the truck. If I think somethings about to go down, I pop it in neutral for normal braking. Locking the transfer case (fulltime np203) will also stop it from doing this.

I've pretty much replaced all the mechanical parts of the brake system over the time I've owned it.

Except one.. The Combination valve.

Could it be the problem? I feel I've exhausted everything else. Bleeding, adjusting, pushrod length, drum brakes. Things have improved since I've purchased the truck but, their still not where they should be.

1977 Dodge W200

Have you ever replaced the rear break hose, the one from the axle to the frame.

no I haven't

I remember seeing it when I was working underneath the truck and it appeared to be newer or at least the outer jack looked intact.

Good Point....Outside mite look good... But the inside might have a issuse

I went back out to shop today to take a better look at the combination valve. I read it has a stem on it that moves when the brakes are pressed. Mine moves, which usually means the combo valve is working fine.

I also didn't give the rear brake time to seat back in after turning the drums. I drove it little and it seems to feel better.

But, I think a big point I missed is the truck it itself.

This blue truck doesn't have it's original box anymore. It has a wood flatbed with a hydraulic dump which I'm sure is way heavier than the stock box.

And I've been comparing it to my other W200 that still has it's factory box with nothing in the back.

So, I don't know. Like I said I can stop fine. Maybe I'm just over reacting.

I could still replace that hose just because though.

it's a 77 M880 rite?

Correct. Both trucks are.

Do you have the M880 repair manual?

http://imfmotorpool.com/DODGE_M880_Manuals.html

Should stop without an issue … Hummmmm
:thumbsup:

Thanks for the link. I've seen similar manuals posted over at steelsoldiers.com

I also have a Chilton and Haynes book for my application. I always try to get information before doing a job but, I don't always listen to what the manuals say.

For example one of the manuals told me to remove the radiator to replace the water pump.... yeah that didn't' happen. There was plenty of room to work with the rad in place.

I am going to go ahead and replace that brake hose.

I agree somewhat... Mostly I think my point was going to be that I think the truck can handle the extra weight with the dump body. Simply because the truck has been MIL. spec'ed to handle it. Just need to look a little deeper to find out what the problem is. But I'm sure you will find it sooner or late..

Did you have the brake shoes arced to match the drums?

no. Is that something that's still common?

Plus, the shop I have access to has no such equipment, just a brake lathe.

Oh, I Agree. I never doubted the truck couldn't handle the weight being the M880 is a 3/4 ton truck rated by the military as a 1 1/4 ton. I just wonder if the weight difference over the rear axles affect how the brakes apply because of the combination valve. I've seen proportioning valves on other vehicle applications with a cable or linkage that adjusts based suspension load.

I wish the hydraulic side of brake troubleshooting was more in-depth. Like flow, pressure, etc. Troubleshooting procedures beyond the common stuff. I want to be able to prove something is faulty not just replace it. For example that combination valve, I assume it works, I can't prove that it does.

I think hydraulics are cool...but, their weird. I wish troubleshooting was more like electronics using a meter.

Anyway, I'll replace that hose and bleed the system again.

I had a friend drive it for a bit and they don't think anythings wrong.

I don't know. At least the rear brakes don't squeal anymore, I can't tolerate noisy brakes.

Not so common, but a must do for proper drum brake function.

https://www.jalopyjournal.com/forum/...-shoes.317327/

Quit possible you got ahold of some soft brake lining... But the sign you get with that is a spongy brake pedal.. But someone has to really be looking for it to catch it....lol.
Not sure what you had installed.... But for the fronts on most of our MIL. outfitted stuff, will run "Performance Friction" Carbon Metalic's… These have worked out very well for us. Last a long time, 4 times longer... >>>>> https://pfcbrakes.com/ <<<<<< Just food for thought....

Oooo boy. Well, I went into the shop at around seven Sunday evening thinking I was going to change out a few brake hoses real quick and ended up staying until 11 making a new brake line for the rear.

It turns out someone had replaced the rear brake hose before but, the fitting was seized to the brake line so, they left the hose unlocked from it's bracket and screwed the hose onto the seized fitting.

I tried to break it free but, ended up making the line leak instead. So, I replaced it and put it back together right. No Mickey Mouse repairs on my rigs. :naughty:

I bled the brakes today and the pedal feels firmer than before. Still not exactly like the red truck but, I'll take it for now. The truck stops fine and I have other things I need to attend to.

RacerHog, Regarding the brake pads, both trucks are running a house brand semi-metallic from either O'Reilly or Napa can't remember which. Thanks for the link, I'll consider those the next time I service my front brakes.

Thank You All for your help.