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| | | | Joined: Mar 2017 Posts: 299 'Bolter | | 'Bolter Joined: Mar 2017 Posts: 299 | Ok, Here we go. I replaced the single brake master cylinder with a dual brake master cylinder. I also replaced the wheel cylinders, brake lines, hoses, springs, everything. So, I know I have drum front and rear brakes.My question is, do I need a proportioning valve? I haven't found any information on a Drum/Drum, needing a proportioning valve. If it was disc/drum then yes, you need a Proportioning valve. Help!!! If I drive down the road, And hit the brakes like in a panic mode. The rear end locks up. The front, not so much. The truck has a 235 and My new 410 gears in the rear end. I can get up to 60 miles an hour. I should probably convert to disc front brakes.
What do y'all think?
Elmo | | | | | Joined: Nov 2005 Posts: 6,101 'Bolter | | 'Bolter Joined: Nov 2005 Posts: 6,101 | Hy Elmo, drum/drum brake systems do not require a proportioning valve even when they are "powered" by a dual master cylinder. Rear brake lockup is pretty common in unloaded pickup trucks, especially in panic stop situations | | | | | Joined: Mar 2019 Posts: 1,003 'Bolter | | 'Bolter Joined: Mar 2019 Posts: 1,003 | Ditto to 3B. Rear lockup in panic stops are just what they do. Try alitta lower rear tire pressure if you dont use it loaded alot to capacity. Theres really nuttin to fix. They are actually working. You might even be surprised how good it stop in panic mode loaded. Makes sure the front are properly adjusted as well. Give yourself alitta space in front of you till you get familiar with the stopping availability. | | | | | Joined: Mar 2017 Posts: 299 'Bolter | | 'Bolter Joined: Mar 2017 Posts: 299 | Thanks guy's!!! I have a feeling it's just the fact that I'm so used to the modern vehicles ability of stopping on a dime. It took me a while to get used to the way my truck steers with the NON independent front suspension
Elmo.
Last edited by Elmo; 05/29/2021 11:49 AM.
| | | | | Joined: Feb 2004 Posts: 29,886 Kettle Custodian (pot stirrer) | | Kettle Custodian (pot stirrer) Joined: Feb 2004 Posts: 29,886 | Weight transfer and traction has a lot mote to do with stopping than the design of the brake system. It's not uncommon for the front brakes on any vehicle to do 70% or more of the stopping, due to weight being transferred forward during a stop. Add to that the fact that truck brakes are designed to handle a fully loaded vehicle, and rear wheel lockup when unloaded is pretty much a given unless some finesse is applied while stopping. "Finesse" and "panic" don't always go together, but the final factor is always "traction".
Jerry
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| | | | | Joined: Mar 2019 Posts: 1,003 'Bolter | | 'Bolter Joined: Mar 2019 Posts: 1,003 | Ditto again to Hotrod lincoln . Do alitta experiment. Put a ton of gravel in it and duplicate the "panic stop". You might be surprised.?..  | | | | | Joined: Jun 2011 Posts: 5,096 Crusing in the Passing Lane | | Crusing in the Passing Lane Joined: Jun 2011 Posts: 5,096 | GM and someToyota trucks have a factory proportioning valve hooked to the rear suspension so when loaded, more rear pressure is applied. Adding one of these valves should be relatively easy. Observe how they are hooked up and then copy.
Ed
'37 GMC T-18 w/ DD 4-53T, RTO-610, 6231 aux., '95 GMC running gear, full disc brakes, power steering, 22.5 wheels and tires.
'47 GMC 1 ton w/ 302, NP-540, 4wd, full width Blazer front axle.
'54 GMC 630 w/ 503 gasser, 5 speed, ex fire truck, shortened WB 4', install 8' bed.
'55 GMC 370 w/270, 420 4 speed, grain, dump bed truck from ND. Works OK.
| | | | | Joined: Mar 2002 Posts: 9,115 'Bolter | | 'Bolter Joined: Mar 2002 Posts: 9,115 | I found the rear wheels would easily lock up on my 1 Ton, on gravel etc. I don’t carry loads so I installed a proportioning valve for the rear. That solved the problem. | | |
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