[kwrangln]

The truck...

01 1500 qc 4x4, 5.9, auto, 85K miles, no mods.

The problem...

The rear brakes like to lock up with minimal pedal effort sometimes. Its not an every day thing, and not just after its been sitting a while, its completely random. Happens only at low speed. Pads and shoes are good, everything looks ok in the drums. Sometimes it feels like it takes more pedal effort to stop from speed, then when the speed gets low enough it locks hard enough to get the rear tires to skid on dry pavement.

So, where the heck do I start? Anyone else ever have this problem? I experienced it before on a 3500 2x4 but we didn't do maintnance on it (was a GSA vehicle) and the shop never did get the problem to go away that I know of.

My initial thoughts are something wrong in the front brakes, maybe sticky calipers so more force is required to move them, in turn putting more force to the rears causing the lock. Only problem with this theorie is when traveling slow it takes so little pedal effort to lock em up. Maybe a preportioning valve problem?

I just spent the last hour searching and reading brake threads here, but its possible I missed something, so if its already been adressed please point me in the right direction. I did find one thread mentioning rear brake lockup from jan of 06, but it had no replies.

I'd prefer to not start randomly throwing parts at it till I by chance hit the right spot.

Thanks.

 

[Hollister_crusher98]

if its drum, its probably just water inside of it... i have had this problem a few times, try going in reverse and slowly applying hte breaks, for some reason it doesnt lock up in reverse.... only forward....

 

[CoastieJack]

If you apply the e-brake does it do it too? I'm thinking something with that, or if not the ABS. (That would suck and be very expensive)

 

[kwrangln]

On 2007-12-07 21:59, Hollister_crusher98 wrote:
if its drum, its probably just water inside of it... i have had this problem a few times, try going in reverse and slowly applying hte breaks, for some reason it doesnt lock up in reverse.... only forward....

I would buy water in the drums if it only happened on rainy days or after the truck had been sitting for a while to develop surface rust on the braking surfaces, but it will grab after driving 35 miles from work to the house, plenty of time to dry things out. It has also happened on warm sunny days.

On 2007-12-08 16:54, CoastieJack wrote:
If you apply the e-brake does it do it too? I'm thinking something with that, or if not the ABS. (That would suck and be very expensive)

Hey, another coastie, greetins machinery killer. DC2 here. Here's the truck in question, and my project heep in front of my last unit.

E-brake functions normally, no issue there. Hope the ABS is ok, not getting any kind of warning, so keeping my fingers crossed.

I'm still thinking front caplipers of prop valve. Had it happen a few times today. Most of the time the pedal is nice and firm, starts braking right at the top of the travel. When I have issue the pedal travels beyond the normal braking point, ya know, get to where it usually starts slowing down, but doesn't seem to be reacting so apply a bit more pressure, then bam, the back tires are sliding.


Someone has to have had this issue before, course that would be just my luck, come up with an entirely new issue that takes forever and a metric crapload of cash to figure out.

 

[Lance]

is it both rear tires or just one? my beater car is doing the same thing, only one tire is locking up though. it has a new wheel cylinder. I figure the opposite side is frozen causing all the brake pressure to go to the one side. going to change the other wheel cylinder soon and see if it fixes it

 

[kwrangln]

Its both rears.

 

[general--lee]

do they have a valve for applying more effort when the bed is loaded if so its probably that

vans have them over and they always causing rear brake lock up but as i say im not sure if your truck has one ???

 

[kwrangln]

Assuming (yea I know what that means) that a load sensative valve would be attached to the frame and axle so it could sense ride height (like toyota trucks have), I havn't seen one on there. I dont know of any other way a load sensing valve could work or what it would take refrence from if not the axle to frame seperation. With that said, I dont believe such a valve exists on the ram 1500's.

 

[Hollister_crusher98]

yes dodge trucks do have this, its on the drivers side of the rear axle...

I have the same problem, i apply teh brakes, seems like its slowing down, then it kinda stops slowing down, so i have to add more pressure. but my tires do not lock up.... :wall: they only do it when it's wet.

 

[brockbeag]

Couple of tips, some I learned from expierence,some I heard or was told, and some where picked up at the school of hard knocks.

Tip 1: brake fluid does "wear out" over time and loses heat resistance. Hint it will boil, so after 100,000 miles change it.(when changing front pads loosen the banjo fitting at the caliper and bleed the fluid out as you are pushing the piston into the caliper. Also never a good idea to push back through the brake system if equipped with abs without bleeding fluid out, it can cause damage.)

Tip 2: when changing a questionable/faulty wheel cylinder, change to opposite side as well, think of it as cheap life insurance.(just like you should be doing on the front unit bearings)

Tip 3: when doing a rear brake job, change all of the mounting hardware and springs with new ones. The constant heat cycling will weaken springs and can cause one side or the other to "grab".

Tip 4: A leaking axle seal or wheel cylinder can cause one side to grab or lock up depending upon severity of leak. Just something to keep in the back of your head.

My Ram had issues with what I thought was the right rear brake "grabbing" when I bought it. I bought a pair of wheel cylinders, a set of drums, a set of pads, and I did not buy any hardware kits. I proceeded to tear the right side down,everything looked good including the pads but I changed everything but the hardware. Same senario on the left side, except I noticed the lowermost spring was a little stretched. One more trip to the parts store and two hardware kits later I had perfect rear brakes,lesson learned . So don't skip on the details when it comes to brakes, you, your family's, and me and my family's safety depends on it. Hope this might help someone out eventually.

 

[Wisky]

Did anyone ever come up with an answer? My 2000 dodge ram 2500 does it.