Help! Just got a 2007 Kenworth T800 triaxle and I can't operate the steerable lift axle. The truck is from the South Carolina area, but now is out West and needs to meet WA State DOT. There is a Handle to turn on the dash. I believe this regulates the pressure. There is a pressure gage on the dash. I do not see a pressure gage on the outside the cab which I believe is required in WA State. When I turn the handle, nothing happens. After the truck has been sitting for a few days, the axle slowly drops down to the ground. Starting the truck and filling the air tanks slowly raises the lift axle. Going in reverse raises the lift axle. There is nothing between the seats that I can see that is a switch as all there is only the controls for the PTO for dump, air gate, and pull tarp. What am I mission. Handle looks like a Sealco 5400. Brand of the axle is Watsun. Any help with all this would be fantastic.
Have you hooked up to a trailer yet? Some lift axles are plumbed so that the axle will not drop until the air lines to trailer are connected and the emergency side {Red Knob} is pushed in. On those set-ups you can use a dummy glad hand plugged off and connected to the red air line-push red dash valve in and axle will drop. But it all depends on how it was plumbed. You can install a dash switch for raising and lowering. Parker makes the pressure regulator for the outside of cab installation.
All of my later model lift axle equipped trucks require that the parking brake be released before the axle will lower. This is done to prevent a rollaway condition should the primary suspension bags deflate while parked, since lift axles aren't equipped with parking brake chambers.
Thanks for the reply. The truck does not have a red button on the dash, no air to the back, and currently no pintle hitch trailer set up. I will try releasing the parking brake and see if that does anything. Once you release the parking brake, do you turn the handle to the right to apply pressure to lower the axle to the right pressure? To raise the lift axle, do you turn the handle to the left, to release the pressure, the gage goes down to zero, and the lift axle come up? Does anyone know if a pressure gage is needed outside the truck by the cab in Eastern States. This one doesn't have one outside. CDL drivers out here in Washington State say that you do need one on the outside of the cab. What is the best way to know what pressure to apply?
In Washington State the pressure regulator must be mounted outside of cab, with the pressure gauge mounted in dash and raise lower switch in dash. Wa DOT does not want the driver to have the ability to raise and lower pressure on the drop axle when crossing scales. But in slick conditions a driver needs to be able to raise the drop axle to put more weight on the steer axle. There must be a switch located somewhere in the cab. Most of the drop axle manufactures went to a single full function valve, it's the only way to fly. The old Parker/Norgren valving was a real problem, i don't remember the part number for the full function valve but I keep one on the shelf at work, I will post the part number in the morning.
Parker regulator #14R013FC, Full function drop axle valve #GTD 5040 411 01.
Can you tell me where that part might be in the truck? I have found what looks like that part when I lift up the engine hood, and up on the firewall, near where the Pressure valve is. I'm going to see if I can track down the last owner of the truck and get info from him on the lift axle operation. Do you know of any good dealer in Seattle that would be good to work on this, and can install the exterior pressure regulator by the cab?
I live in S.W. Wash so I have limited resources on who to take it to for repair other than the dealers, and those are all pretty much the same. Normally the regulator is installed right behind the cab on left side. The air valve would or should be located left side/inside of frame just in front of drop axle, normally attached to a crossmember.
Ok, think I got it. I found the right rocker switch on the dash. In order for it to work, you release the air brake. Then the steerable axle drops down. Then turn the handle to bring the pressure up. Does 50 psi sound about right for a 16.5 box and Watsun 13200? How do you test? To raise, put the allison Auto in Reverse. Put on the air brake. Or release the pressure and move the rocker switch. Anyone know the process on a 2007 Kenworth T800. Lift axle is OEM.
Normally on our rigs it takes about 70 psi, with 9,000 on the tag 12,000 on the steer.
Many thanks for all your help! Is the exterior gauge showing the PSI like the one inside the cab, or does is show the pounds of pressure? At what point do I need to use the lift axle. The truck is licensed for 70,000 GVW right now. If I have just 6 yds of gravel, do I need to put it down. With 10 yds of gravel, I would put it down with a bit less pressure? With 12yds, (36,000 lbs), then down with most pressure. Lighten it up with slick conditions to get more weight on the steers? What does WA State patrol want to see? When you back up the lift axle raises. Does this mean it's ok to dump with the axle raised?
My opinion is that truck would be good for 56,000 lbs in Washington. 34,000 on the drives, 12,500 to 13,200 on the steer and the rest on the drop axle. Anything below 48,000 leave it up, above that weight put it down. You need to load up to legal weight then put your steer axle on a scale and adjust the lift axle pressure until you get what you need, then check with the steer and lift axle on the scale and make sure it is at least 22,000. 70 psi should get you close. Then don't mess with it. Leave it up when you are dumping, backing up or off the pavement. Also in slick conditions. I can't tell if the truck has airbag suspension but if so dump the air when dumping the load, to make it a little more stable and also to keep from yanking on the shocks when it tops out the airbags when the weight all comes off at once. Looks like a nice truck!
The truck has 23,000 lb rear axles, and 8 brand new 16ply retreads. The suspension is Haulmax. The front steers are 315/80R/22.5. This was never a tractor. Why would the truck be only good for 56,000 lbs? Empty weight is 28,000lb. So I can only haul 10 yds of gravel? I only licensed it for 70,0000. My plan is to haul 15yds of dirt, and up to 12yds of gravel. Where does one go or do the scale info?
tandem drives 34,000 max , 14,000 steer axle w/315, 8,000 on drop axle (drop and drives usually 42,500 legal bridge)
Thanks for your help guys! But I'm still stupid on this. What does that mean 42,500 bridge legal? What is the max weight fully loaded I can carry legally then ON WA state roads? What is max weight I can tow? All I'm used to is my International 4900 with air brakes licensed at 38,000 GVW and eager beaver tag trailer for my 14,000 lb mini.
bridge formula= how much weight on set of axles depending on wheelbase. 3 axles = center of drop to center rear axle, 10 feet= 42,500. overall weight for 4 axles probably about 56,000 gross. how many trailer axles? wheelbase?
In SC, that truck was legal for 70,000 with the axle down, and 50,000 with it up (if you stayed off the interstates). The pressure not very critical as long as you have no more than 20,000 on any one axle, and you wouldn't want to frequently overload your steer axle. If you got on the interstate, you had to comply with fed bridge law, so nobody would drive that loaded on the interstate.
FYI, the length of the box is 16.5 feet. I haven't measured the axle distances yet. This truck is from South Carolina.
Yep, that's why I mentioned what it was legal for here. It could gross 80,000 with any trailer here, as long as no more than 20,000 on any axle.
This might help, it is definitely confusing figuring all this out. https://www.dropbox.com/s/9j30pj0t4ozt0y7/AxleWeightTable.pdf?dl=0
https://secure3.wsdot.wa.gov/commercialvehicle/permits/public/AxleSpacingReport.aspx You can measure your truck axles, fill out this report and should tell you legal weight, and permit able weight. my regulator for my drop is inside the compartment of my sleeper, with gauge. So it can’t be messed with by the driver while driving, or POS people in a lot. I haven’t had any issues with it with dot. I am not a dump Trk however.
Thanks for all the info and help. I had Pape Kenworth install the outer guage and handle. I will see if I can get a real number on my load capacity. Seems like 10yds of gravel, 14 yds of dirt, shooting for just under 15tons load. I see trucks with 56,000lb solo stickers, but higher GVW. As I have paid for a GVW of 70,000 for now, does this mean I can tow my mini excavator with load? Can I tow say, six yards of gravel (Lift axle up 18,000lb), and tow mini excavator Takeuchi TB153FR (13,000lb) and Eager Beaver equipment trailer, 7,500? Truck weight is 28,0000lbs. Questions: Do I load truck with Lift axle down or up? Must be up I think, as when air brake is on, lift is up. Once lift axle is down, leave it down all the time (steerable axle) until I get to the dump location? At the dump site, Lift axle and back up (backing up raises it) and dump. It's Haulmax suspension Once lift axle PSI is set, just leave it alone? Don't adjust per load or weather? Does WA State patrol at a weight station just check to see if you have the lift axle down and "reasonable amount of pressure". or do they weigh your load and say, sorry your at 70PSi, now you have too little on your steers, you should have it set at 67 psi? Better to have too much weight on your lift axle, or too little? Some people say leave it at 50 psi. I've never been in a weigh station, and I'm scared!
Get a load and go play on a scale, see what does what, and take notes. When I’m helping my excavator on the truck I have my tag at 40psi. If I have a heavier load or rear heavy load I’ll bump the pressure as required. Fully loaded I can crank the pressure up all the way and not overload my steer, although my tandem (single drive plus tag) could be overweight.
If you are still looking for a good shop in the Puget sound area look up Scott Latherow Repair.
Dodge the scales at all costs! In Washington you are required to have your drop axle(s) down when loaded, regardless of weight.
Just want to add, once you get your weights figured out and set the pressure on your lift axle you don't want to be messing with the regulator all the time. You just use the dash switch to raise and lower it. It goes up in reverse to prevent damage if you forget to raise it on your own. Get in the habit of raising it when you pull into the jobsite.
So I took the truck to Pape Kenworth and they have moved the pressure gauge to the outside. Did a good job, but a big hassle. They did not want to use the original handle which was working fine, but they finally did. They charged $243.81 for a $35 gauge! A metal bracket cost $156.84 and I had them install a new panel cover to cover the interior dash hole to complete the new oem look for $$189.58. Don't ask about labor! The exterior gauge is set to 60psi. I haven't done the scale thing yet. The interior gauge reads 51psi though! Regarding the lift axle down when loading, is that best for the truck or just needed for the State? Seems like you can do whatever you want until you touch a Public roads. I hauled a couple of loads of 12yds of dirt this week.
You'll save yourself a ton of money if you can take care of simple mechanical work yourself versus going to the dealer. In regards to using the lift axle, I'm not familiar with your state laws concerning axle weights and when you're required to use the axle, but I can give you some general guidelines. First thing you need to know is your empty weight. Next you need to find out your max legal weight with all axles on the ground. Comparing these two numbers you'll know how much payload you can legally haul. You'll also want to determine the max legal weight of a tandem axle/ten wheeler dump truck, for those times when you're only hauling a partial load. If you only have a few ton on, then you likely won't need to use the lift axle to maintain legal axle weights. If you're running at your max weight or near it, then you'll absolutely want to have that axle on the ground while on public roads. When you pull out of the jobsite or quarry, put it down. When you pull into the jobsite or wherever you're dumping, lift it up. Out on the road you want it down both for your own benefit and to make the state happy. While running your max weight, having the axle down will prevent components from being overloaded, it will provide you all of the available braking your truck has to offer, and will be more stable than having it up in the air. Hope this helps.
The truck has axle temperature gauges in it. The front one runs hotter than the rear which I think is a bit normal. With the lift axle down, will I see a lower temperature on the front axle? Also, does anyone have a temperature gauge on the lift axle?
No the lift axle isn't going to affect your drive temps. Those are measurements of the gear oil in the differentials, which is dictated basically by how hard you're working the truck. Light loads no hill=low temps. Heavy loads pulling long hills=higher temps. You should realistically never reach problematic numbers in a dump truck, the weight just isn't there to put enough strain on the truck. If you do see temps climbing into the red then that might be an indicator of a problem within the axle. As an example, guys that will see those temps rise to dangerous levels are generally heavy haul dragging 150k+ uphill for miles.
The other thing that will cause you to see high axle temps is low oil level. Like hwrdbd said, you won't see a temperature gauge on a lift axle because it doesn't have gears.
Many thanks for this information. Is there any issue with a steerable lift axle to make as tight a turn as you can loaded with the lift axle down? Is the tire sliding a bit or still rolling on a super tight turn when you have the steering wheel all the way turned? This would be making a tight U- turn in a parking lot, or at the end of a street, or onto a narrow side street etc. My lift axle tires have a lot of tread, but the tread does have some uneven tread wear.
Personally if I'm in a truck like yours I will still lift the axle on a super hard turn. Normal intersections aren't a problem, but if I was doing any sort of U turn I would definitely lift it. Just use your judgement, if you think its a really sharp turn then lift it. One caveat to this- before you go lifting the axle on a public roadway make sure there aren't any cops around. I'm sure some won't bother you if they see you lift it momentarily for a hard corner, but I know for a fact that some will stop you for it. Depending on what sort of uneven wear you are seeing, it could be a few different things. One of the most common I see is flat spots, usually caused by locking up the brakes. When you first lower the axle it takes a few seconds for the bags to build enough air pressure to actually put some weight on the axle. You want to avoid using your brakes right away if at all possible. Imagine you pull out of the job, drop the axle, and two seconds after you flip the switch a car cuts you off forcing you to slam the brakes. 99% chance that you're going to lock up the brakes on the lift axle and possibly flat spot the tires. I'm not sure what your tire setup is, but many guys will run the steer tires down a ways, then swap them onto the lift axle and buy brand new steers. I would say this is most common with 385s and 425s. I say this because it is possible that the tires on your lift axle were used when put on, and may have been worn oddly from before.
Very good info. I was reading up about when to lock the rear axles together for more traction. There was no info on locking the rears with the lift axles. Just don't go over 25mph etc. I suppose if you backed into an area to dump and the rear wheels were slipping upon leaving you could lock the rears and move out in low, low gear. Putting the lift axle down might lift the truck a bit out of the rut, but then would you loose traction? Any thoughts on that? My suspension is Haulmax. Also, yesterday when I was leaving the place where I was loaded where the dirt and gravel road was rough it seemed like I could hear rapid air escaping. Does the lift axle suspension work by quickly releasing air from the air bags as the lift axle go up and down over speed bumps and rough terrain. I don't think the pressure gauge in the truck moved.
A lift axle kills your traction. Anytime you need traction, you must lift it.
Ya when you're offroad you want your axle up and as much weight as you can get on the drives for traction. I'm not sure what locking setup you have in the truck, if just an interaxle or full lockers. I wouldn't worry about running lockers at whatever speed, just make sure that you aren't already spinning if you're going to engage any locker. If you do have full lockers you aren't going to have quite the same turning capability if you have them all locked up. It will want to push you straight. Just be careful with the full lockers though, only using when you're on slippery stuff. You never ever want to lock everything in on pavement and try to turn, especially loaded. Make sure you get them disengaged once you get out of the mud/snow/whatever and before you get yourself back on the road. In your scenario of slipping as you pull back out after dumping, you would stop the truck and lock up, get yourself out to solid ground, then just flip them back to the unlock position-no need to stop to unlock. It can work just like 4x4 in a pickup, and maybe take a little bit of distance for them to actually disengage. In regards to the air you're hearing, yes that is just the bags on the axle dumping air to keep from over pressuring themselves. Your knob adjusts the psi they are supposed to max out at (in order to set desired weight on that axle) and as you drive over uneven ground sometimes the axle will be pushed upward so far that it compresses the bags, effectively increasing the pressure in them. This activates the pressure relief and some air is let out to keep the axle from taking too much weight. Totally normal.
Regarding the drives, which axle is always driving? Is it the front rear axle or the rear, rear axle? I have an Allison RD4500 I'm still learning how to utilize it fully. Seems as though you can put it in drive low, and then even lower the low by pushing the down button. I will have to see which locking rear axle I have. I believe it's just a far switch on the right side of the panel. What do most 2007 Kenworths T800's have? This was always a dump truck. What is the difference between full lockers, and interaxle?
Both axles are always driving, it's just like the differential in a car. Actually, many people are confused about that. An open diff ALWAYS APPLIES EQUAL TORQUE (twisting force) to both sides, or both differentials in the case of an interaxle diff on a tandem truck. When one slips, it can't apply any more torque to one side than the other. All tandem trucks can lock the differential between drive axles, some can lock the side-to-side diff in one or both axles, That's a full locker.
Torque follows the path of least resistance.
Trucks can be spec'd very different from one to the next, depending on who ordered it, where it was intended to run, what kind of job it was meant to do. Post a pic of the switches if you can. If the label isn't worn off the rocker switch it will probably give you a clue as to the locker setup you have. If it is only one switch, then I would guess a simple interaxle lock, but I suppose thats no guarantee. Just to elaborate on an earlier reply, an interaxle locker just guarantees that you are sending power to both drive axles. Each axle would still operate with an open differential, ultimately meaning you will see one wheel spin on each axle if you get stuck. Full lockers would be when you have the interaxle, plus a locking differential in both drive axles. This would guarantee that both sides of both axles would always be turning together.
Ok, here is the switch. I don't think this is full lockers. Seems like at a stand still or less than 20mph, you can flip the switch and your in according to what I have read. If anyone has a specific T800 2007 owners manual, I would love one.
That would be the power-divider lock. You’ll get power to both axles but each axles diff will allow wheel spin- just two drivers spinning instead of three. I’ll kick that in if going up a gravel incline to lessen wheel-hop and washboards gets the drive.
So can I put that on and back up with it? Sounds like if I'm dumping a load and I need to back up into a grassy area, I should put it on. What is the difference between power divider lock and full lockers. Which is better?
Differential let’s one side turn faster than the other on turns. Full lockers keep everything turning same speed- truck will want to push you straight forward.... Locking power divider when off road is fine. You’ll figure out how your rig does on different surfaces. Loaded, you can probably go most anywhere. Empty, that’s usually another story. Be careful, people will ask you to dump in crazy spots. Walk the area if in doubt. Watch to see if you’re leaving ruts if ground too soft. Keep length of truck up/downhill. Don’t dump on sidehills. thankfully never happened to me but, sticky loads can hang up on one side of box- if on sidehill can tip you.
You'll learn as you get more experience in your truck. The more situations you navigate, the more familiar you'll get with what your truck, and yourself, can and can't do. Yes you can use it just as you described. If you're coming into a job and they say hey dump over there and you see something that looks questionable, you should flip your lock in as you're approaching the spot. You'll have a much better outcome if you're locked in and can keep momentum going, vs if you spin to a stop and then try locking in to get moving again. Just be mindful of where you're trying to get into and make sure you have a plan for getting out as well. Some situations allow you to be a little more aggressive than others, ie is there a machine there to drag you out after you dump and can't get moving? Another note, your truck is tough but not meant to be abused. If you're trying to back up a steep hill of loose material you may find that it wants to start spinning on you, even locked in. Just be ready for this, or for a soft spot, or whatever, and be prepared to stop before something goes really wrong. If it starts hopping just stop before you break something. If you're backing in somewhere and start seeing your drives sinking out of sight, just stop. Pull back out if you can. If you can't, dump the load and get a machine to help you.
Back to the lift axle. Upon further inspection there is some welding needing to be done on the frame, and there is some slop in the kingpins. How much slop is ok on a steering lift axle before it needs to be an immediate repair? Hoping to do it next year. We don't drive the truck that much.
Well you probably don't want to see any slop in the kingpins. Something like that could be the cause of uneven wear on those tires.
The tires do have some cupping, although the tire dealer didn't think they were two bad. There is a lot of tread and the tires are not that old. I thought the tire wear was related to the air pressure and load on the lift axle. Besides air bags leaking, what are the major signs when to replace the air bags. I assume you do it as pairs. Mine have some cracks but no leaks. One of the air lines to one wheel was a bit tight/short in the length and will be replaced. It's a nice truck, but a lot of little things to fix and correct. I can't imagine getting an even older truck.
Most people replace the bags on a lift axle right after they hear a BOOM
Understood. Best to wait until there is a loud noise and fireworks. Apparently this was the previous owners maintenance schedule.
I don’t run dump trucks, but do run trucks on our farm. If I have a poor looking bag, I get it ordered and carry it in the truck. If it blows, I have the part to fix it to minimize down time.