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02-03-2013, 02:40 PM
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#1 |
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Registered User
Join Date: Jan 2012
Location: New City, NY
Posts: 32
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Brake issue
Im having an issue with my brakes, when i first drive the truck after its been off for a little while (could be hours, days, doesn't matter) and Ii apply the brakes it seems as if the fronts are engaging before the rears. Im not sure if this is whats actually happening but it jerks the truck forward with only a slight amount of pedal pressure. After the brakes have been applied a few times they operate as normal. The brake setup is hydroboost with rear drums front disc. I was think maybe prop valve or air in the lines? What do you guys think?
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02-03-2013, 10:20 PM
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#2 |
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Registered User
Join Date: Jul 2005
Location: CT
Posts: 278
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Re: Brake issue
Residual check valve in the master or sticking metering valve in the combination valve can cause what you are decribing. Do you have a quick take-up Master?
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02-03-2013, 10:49 PM
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#3 |
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Registered User
Join Date: Jan 2012
Location: New City, NY
Posts: 32
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Re: Brake issue
I dont think I have quick take up, im running the stock calipers so i wouldn't think the p.o. would have installed one.
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02-03-2013, 11:59 PM
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#4 |
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Moderator
 
Join Date: Oct 2008
Location: Wentworth, NH
Posts: 4,977
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Re: Brake issue
Download the 1982 service manual PDF from the thread in my sig. Look at the brake troubleshooting section starting on PDF page 525.
"Grabby brakes. Faulty spool action caused by contamination in system. Flush steering system while pumping brake pedal." --Hydroboost troubleshooting page 525 1982 GMC Light Truck service manual
__________________
1959 M35A2 LDT465-1D SOLD 1967 Dodge W200 B383, NP420/NP201 SOLD 1969 Dodge Polara 500 B383, A833 SOLD 1972 Ford F250 FE390, NP435/NP205 SOLD 1976 Chevy K20, 6.5L, NV4500/NP208 SOLD 1986 M1008 CUCV SOLD 2000 GMC C2500, TD6.5L, NV4500 2005 Chevy Silverado LS 2500HD 6.0L 4L80E/NP263 2009 Impala SS LS4 V8 RTFM... GM Parts Books, GM Schematics, GM service manuals, and GM training materials...
And please let us know if and how your repairs were successful. |
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02-04-2013, 12:36 PM
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#5 |
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Registered User
Join Date: May 2007
Location: New Hampshire
Posts: 349
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Re: Brake issue
Check that the shoes in the rear drums are correctly installed. A full axle brake set comes with 4 shoes that look almost identical but 2 of them are the leading (front/secondary) shoes and 2 are the lagging (rear/primary) shoes.
Because the steel frames are identical and only the size of the lining difffers, it is easily possible to install them incorrectly. Any number of wrong installations can cause severe brake shudder especially on the first couple of stops or when it is wet/humid out. You can have the leading and lagging reversed on one or both wheels, 2 leading shoes on one side and 2 lagging on the other, etc.  
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