front brakes pulling to the left

I got an odd problem on 92 kenworth w900. When I step on the brakes it pulls to the left. Does it worse when the truck is loaded. I just put new shoes and drums on the front. It pulled before new shoes and drums and still pulls. S cams looked good. I thought maybee I had a broken slack adjuter but when you apply the brakes it looks like everything works and moves like it should. Has anyone ever seen one line get partially plugged on one side and cause an imbalance? This is puzzling cause all the parts look good. When you adjust the brakes the left one always takes a bunch more adjustment than the left.

You could have restricted air line but I would run the brakes up tight and back off 1/2 turn measure the slack adjuster travel with brakes applied.
Drive it around and remeasure the travel. You probably have a bad slack adjuster. How does it act with both wheels adjusted the same? Does it
have a LQ-4 valve/relay limiter? It will have one supply line and the other two are delivery to the front air cans from that valve.

Truck Shop

Does the truck veer to the left, or does the steering wheel pull hard to the left? If the wheel doesn't try to yank itself out of your hands, I would suggest checking the brakes on the drivers.

workshoprat92 said:

I got an odd problem on 92 kenworth w900. When I step on the brakes it pulls to the left. Does it worse when the truck is loaded. I just put new shoes and drums on the front. It pulled before new shoes and drums and still pulls. S cams looked good. I thought maybee I had a broken slack adjuter but when you apply the brakes it looks like everything works and moves like it should. Has anyone ever seen one line get partially plugged on one side and cause an imbalance? This is puzzling cause all the parts look good. When you adjust the brakes the left one always takes a bunch more adjustment than the left.

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A lot of useful info here. Truck Shop is spot on, though. You need to get both sides adjusted as close to identical as you can. Does it have automatic or manual slacks? If you have manual, the half-turn method is a good starting point. With autos, as long as they are identical, you could set them up the same way. You are going to need someone to help you though, maybe even 2 guys. One guy is in the cab stepping on the pedal, and the other 2 are measuring travel. I would start by having the guy in the cab only put a small amount of pressure on the pedal, if you.have an application pressure gauge, that would be great. Start with about 30 psi, then 60, and so on up to full pressure, measuring each time. This could get interesting. You stated that the left side always takes more adjustment. If you have manual slacks, then you most likely have some other issue. Autos, probably a malfunctioning slack. It may seem like I'm rambling on, but there are quite a few things you're going to need to check, and pressure is definitely one of them, but I wouldn't go that far until I'd have checked everything else. Jack it up, pull the wheels and drums, unhook the chamber from the slacks and manually move each cam to make sure the right one moves freely. This might seem stupid, but are both chambers the same size? As far as your comment about the problem being worse when loaded, that is because you're applying more pressure to stop. Good luck.

Well I am driving it today and with hands off the wheel and brakes applied it does not pull the whee. As soon as you let off brakes It goes right back straight as a string and steering wheel position dosent change a bit. Thinking suspension? Rear suspension Is all brand new. Manual slacks. I will write more when I get to a regular compiter and not typing between stops.l

Something else the rear brakes are deficent and are scheduled to be done. Still in 26 years of doing this I have never seen deficient rear brakes cause a differential braking situation. Rear suspension brand new and absolutely nothing obvious on the front like loose spring hangers and such. Just proves every once in a while your gona get a head scratching brain stumper!!

I have two thoughts here...get a buddy and a piece of EMPTY road that is in good shape. Get going about 25 mph, empty and LOCK the wheels. See if ALL your skid marks are of equal length. That will tell you if all wheels are locking under heavy braking. Use your buddy as an observer, something on the right side is NOT locking.

I troubleshot a light truck of mine, hard pull to the left on brake application...pulled the front drums and both sides looked great, put new linings front, still pulling...turns out, the front right drum was a bit oversized, AND there was a small fray on the self adjustor cable causing a hang up, so as the front right shoes tried wear in, they were not adjusting causing the pull. A new self adjustor rebuild kit fixed that. Then I thought to pull the rear drums...SOMEONE, who I shall not name, years earlier, changed out the rear axle seals and bearings, cleaned up the shoes, DID NOT CLEAN ALL THE OLD GREASE OFF THE BACKING PLATE AND LINKAGES. When new brakes were ordered for the back, from town, parts runner got wrong shoes (wife), so the brakes were cleaned and truck reassembled. Years later, the truck started doing work in the mountains vs the flat plains of East Texas, got the rear brakes HOT going down a mountain or ten, with a full load. Grease melted, got back all over the shoes.

So we had a combination of factors, all four brakes had good linings and were properly adjusted, but poor contact patch on front right and back brakes had grease contamination.

Howard

KW is known for having weak u bolt torque. Look at the u bolts where they pass through the axle. If you see any rust chances are they are loose and your axle has been shifting.
Has your steering wheel ever taken a different position after a hard brake or a big pothole ?

I hear ya on the buddy thought. Hard to find anyone who knows what they are looking for. Crazy idea! Thinking of getting a go pro camera! on the u bolts they all look tight as a tick. Its a dump truck so 10-4 on rough terrain and hard hits but steeting wheel has always stayed centered. Like I say I been doing this 26 years and even held ase master heavy truck cert at one time so I do know all the point to look at and what to look for. That being said usually there is something that always stands out and points to the culprit. I have never seen one with such a hidden non visible issue. Everything looks as it should be. Keep the sugestions coming as sometimes a mechanic can get mental block and need fresh perspective.

I know it shouldn't but it doesn't happen to have abs ?

No on the abs.

More and more I think about this it has to be a frame and or suspension issue. If it was in the front brakes it would pull the steering wheel which it does not. Rear brakes causing differential braking maybe? Guess I really need to get my rear brakes 100% first just to rule it out.
From there if it still exsists then I gota figure out how to have it show its ugly little head.

I have heard it said that one rear brake 100% and the other 0% and you will not feel a pull.

I believe it.

I had a 2 axle truck where one rear auto slack broke and backed way off and all I noticed was that the parking brake did not hold so well on hills any more.

workshoprat92 said:

More and more I think about this it has to be a frame and or suspension issue. If it was in the front brakes it would pull the steering wheel which it does not. Rear brakes causing differential braking maybe? Guess I really need to get my rear brakes 100% first just to rule it out.
From there if it still exsists then I gota figure out how to have it show its ugly little head.

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One thing to check on a Kenworth is the plate that mounts the power steering box and drivers side front spring mount. I've seen a few of those work loose on dumps and mixers. Not saying that's the issue but it's something to check out. Normally it just makes a "pop" noise when the driver dry steers a loaded truck, but it can move the spring mount slightly too.

Birken Vogt said:

I have heard it said that one rear brake 100% and the other 0% and you will not feel a pull.

I believe it.

I had a 2 axle truck where one rear auto slack broke and backed way off and all I noticed was that the parking brake did not hold so well on hills any more.

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Yea that's pretty much my experience with it also. you can have one rear brake totally not working and all you feel is that you have less braking power. I never in 26 years have experienced a pull from rear brakes. still there is a first time for everything and I have seen weirder stuff LOL.

My big problem is I have to much stuff to fix and no time to do it. Its also hard as heck to get time to do it during the week when parts stores are open. Here in the ozarks its about impossible to pre buy what you need and do it on the weekend unless you got very specific part numbers as the parts guys here really suk so bad. if you cannot pull it off and set it in front of them they are lost. I have started to keep a notebook journal of parts numbers for parts for my truck. that helps a little bit.

RZucker said:

One thing to check on a Kenworth is the plate that mounts the power steering box and drivers side front spring mount. I've seen a few of those work loose on dumps and mixers. Not saying that's the issue but it's something to check out. Normally it just makes a "pop" noise when the driver dry steers a loaded truck, but it can move the spring mount slightly too.

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Ok I will check that. I dont think I have looked at steering box mounting. I dont have any popping noise when dry steering but when ya step on the brake there is some popping up front somewhere. I have no way to know where its coming from and everything looks normal. There is just nothing obvious that I can see.

Ah.... a popping noise up front. You either have a loose spring perch or a bad bushing in the front of the left hand spring. Crank the front brake adjusters down tight as you can and rock the truck back and forth while somebody watches the suspension components.

Like RZ said spring pin bushings and pins. The pins and bushings on a KW are ACME coarse thread and when there worn out they will go to popping at slow speed.
Use a bottle jack carefully between frame and spring to take the weight off the rear shackle some then using a long pry bar between hanger and spring eye check
for up and down movement.

Truck Shop

ACME is the brand Wylie E. Coyote uses

RZucker said:

Ah.... a popping noise up front. You either have a loose spring perch or a bad bushing in the front of the left hand spring. Crank the front brake adjusters down tight as you can and rock the truck back and forth while somebody watches the suspension components.

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Thats a great idea! I been thinking all along it would be nice to lock the brakes on front end and check for play. I was going to do the jack method like Truckshop says when I get time and probably still will. This is what I mean by mental block and you would think a 26 year mechanic would have thought of that LOL. Goes along with what I always say is that there is always something to learn and you can learn something from every person as we all have different experiences. I used to have access to an old lattice boom crane in Denver where I could hook up and lift the whole front end and you could spot stuff like this right away and with ease. I really need to get that crane out here to Missouri but its to big to haul and being that it is Korean war vintage military it only goes 38 mph flat out LOL !!!!

I must work the truck again tomorrow but I will try and get a look at it again Sunday if I have time. I also have a 86 pete that developed a wheel vibration on the RF drive wheel cause the u bolts went loose and the shim to set the camber on the spring and airbag paddle setup either fell out or got ground up. when it is setting on level ground there is a 1/4" gap between the spring and the front spring mount so its not even touching. when you look at it from side to side its very noticeable that the camber on the lh side is set way wrong and no where near what the RH side is. Glad my driver ignored it till i got a chance to drive the truck and say WTF???? Its like when the hell were you going to tell me about this and the the loose pit man arm an the steering box that I noticed right away???? Hired drivers huh??? Hope the pit-man arm and steering box shaft haven't been wallered beyond use!!!

on the rear brakes making it pull it will and scare the s...t out of you if you are not ready for it . 03 mack granite quad dump thats why I asked the abs ?. sensor messed up on one side so not braking on one side driver never said anything I drove it one day holy s...t it would try to change lanes when you applied the brakes loaded or empty maybe because of the camelback flexing on the rubber spring pads but it would dive to one side and you had to steer in the other direction to keep it in the lane.