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Discussion Starter #1
Ok guys I have a FORD question... I know.. I know... I have a 99 F-150 that is locking up on the rear brakes. I've checked the front brakes and they are working correctly. The Wheel Cylinders are working correctly on both sides(drums). All will bleed just like they should. The passenger side rear will lay a good line of rubber just by tapping the brakes and the driver side is a choppy skid. These are kicking in before the fronts do. Any thoughts?
 

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Ok guys I have a FORD question... I know.. I know... I have a 99 F-150 that is locking up on the rear brakes. I've checked the front brakes and they are working correctly. The Wheel Cylinders are working correctly on both sides(drums). All will bleed just like they should. The passenger side rear will lay a good line of rubber just by tapping the brakes and the driver side is a choppy skid. These are kicking in before the fronts do. Any thoughts?
Do you have ABS?
 

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Proportioning/combination valve? Over adjustment? Messed up drums? It can be a few different things. If the brakes were just recently done and were fine before, make sure the right parts were installed. Alot of the Big3 trucks now have a rediculous amount of different parts for the same vehicle. Even when you have all the exact info, the parts are still wrong.
 

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Discussion Starter #4
Yes i does have abs and yes they are the original parts. I was leaning towards the proportioning valve but i wanted to see if anyonecame up with anything different.
 

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Have you tried backing out the adjusters a bit? They (the shoes) should have a slight interference between the drum where you have to mscle them on, but not so mch that you have to hammer them on. After you have them on, don't cinch up the adjuster after you get the drum on there with an interference fit.

If the adjusters are adjusted correctly, You should look at you're master cylinder. Inspect it for any leaks, look for melting/lifting paint on the booster and surrounding areas (indicating brake fluid is getting out, brake fluid eats paint). Also you should be watching the fluid level carefully, if you fill it up and it is going down a noticeable amount over a week or so, you have a leak, possibly in the front circuit. If the leak is in/around the master cylinder, replacing it will likely solve you're problem. If the front circuit is compramised when you press the pedal the rear circuit may be getting the majority of the pressure. Little weight in the back of a truck + weight transfer + mostly/only rear brakes = locked up rears.

Another thing to look at is the emergency brake. I'm not sure if F150's had the divorced parking brake that year, but if they didn't you may have a malfunction with the parking brake cable/pedal/mechanism causing permanent tension on the rear shoe's (the non-divorced p-brake doesn't actuate the front shoes). A pretty easy way to know is if the truck stops as well in reveres as going forward. the non divorced ford parking brakes simply doesn't work in reverse without alot of pressure. Roll the truck forward and let it coast to a stop, then backward at the same speed (on level ground with parking brake off and in neutral obviously). If there is a discrepancy between the distance it rolls forward and back, I would definitely look at the parking brake system. Alternately lift the back of the truck and see if there is a different amount of resistance rotating the wheel(s) clockwise and counterclockwise (in neutral with the parking brake off).Typically its the drivers side wheel that gets more pressure from the parking brake on those (non-devorced p-brake drum brake fords) which opposite of what you're seeing however.

Take apart the drum(s) and see if there is play in the parking brake arm(s) (arm that hooks into the top of the rear shoe) when the parking brake is off, then engage it lightly with the drum apart and make sure it tensions up and isn't just free floating in there. Even if it is a divorced parking brake, check the cables and make sure they loosen up when the brake is disengaged and tighten up when it's engaged.
 

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something is wrong with the brake load sensor. not sure what ford has, but its not uncommon for SUVs to have a simple cable mounted to the axle that runs to the body that senses "sag", which indicates that the vehicle is carrying a load and utilizes the rear brakes more.
is the suspension on your f150 modified? if it is, i bet thats what the problem is.
 

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Ah, Have you checked with the folks at "Ford Truck World"?
 

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Discussion Starter #8
Thank you everyone your help! After reading the posts and looking into the e-brake holding up I found that the wheel cylinder on the driver side was leaking a bit and not retracting fully. I resealed the wheel cylinder, replaced the shoes and all hardware, had the drum mic'd and worked the e-brake cable alittle then did the same to the passenger side just for good messure. All is great now and stops as it should. Thanks everyone for all the great info!
 

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Thank you everyone your help! After reading the posts and looking into the e-brake holding up I found that the wheel cylinder on the driver side was leaking a bit and not retracting fully. I resealed the wheel cylinder, replaced the shoes and all hardware, had the drum mic'd and worked the e-brake cable alittle then did the same to the passenger side just for good messure. All is great now and stops as it should. Thanks everyone for all the great info!
I've had a ton of trouble with the wheel cylinder and drum brakes in general on ford trucks. Two times it has resulted in a complete brake failure, once on the freeway. The cause I've found for wheel cylinders pushing passed their travel is the adjuster coming loose. Usually caused by gold colored ramp which holds the adjuster cable coming out of its centering hole. Just reem the locating flange (on the gold ramp) out a bit and bend its spring a bit more if you ever have this problem with this.
 
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