brake help

[Blackjeep99]

Ok so I have all drums and my back ones lock up before the front do. My dad has a factory disc drum prop valve. Can I put it on my drum system and have it work the same as it would on a diac drum set up? Any other help with this problem would be of great help. I'm bout fed up with these darn drums.

[Mark B]

No you can't. You have to have a drum-drum prop valve. I recently put a power booster on my 4 wheels drums. Search for my post. Something there might help you. My drums set up work great!

[dag19]

How are the wheel cylinders and pads? Good condition?

[El Jay]

Having the rear brakes lock before the fronts is not uncommon.
You have a vehicle that's already light in the rear end (no pun intended), so under heavy braking the weight transfers towards the front, unloading the rear.
So with no weight back there the brakes are going to want to lock.

And as a side note, if you hadn't already noticed, these trucks are notoriously "underbraked", too much vehicle, not enough brake.

[68gmsee]

All good points above. I have a 68 and a 69 with drums and both brake okay, not great though. The problem with drum brakes is that everything has to be working perfectly for all four wheels to brake evenly. All brake shoes have to be adjusted exactly the same and all parts moving and working smoothly. As you know, that's sorta hard to do on these old trucks.

Now, if you do want the truck brakes to be at their optimum you need to insure you get the best brake shoes you can buy and then have the drums turned and if possible have the shoes turned to match the drum circumference.

Make sure all springs are in good condition and brake cylinders, brake hoses, master cylinder all in good or new condition.

If you have added power booster, I'd see if you can get an adjustable prop valve cause as El Jay mentioned, they tend to be light in the back. The way a brake guy told me once is that front brakes should do the majority of the work with rear brakes assisting. Something like a 60/40 percentage.

[hddavis]

if it is locking up when you apply them easy you can try backing up a few times on pavement and hitting your brakes hard. this has worked for me many times in the past. last time about a week ago in my 70 c10 . good luck

[Blackjeep99]

Hey guys thanx for all info. I replaced everything including MC. I got it from adv auto reman delco. I checked all wheel cyl all good no leaks. So my next check was the MC. This time I went to napa.bench Bled it and Swaped them out had my wife help bleed them she is an expert bleeder now lol. And boom I had normal front brakes my back wernt locking up it was the front not working 100% so tHe back was doing most of the stoping. All good now thank goodness I don't think I could get my wife to bleed the system one more time lol thanks again all.