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spankyjr1, Journeyman
Category: Medium and Heavy Trucks
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Experience:  I worked on all types of equipment semis,forklifts,farm,ect.
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We have a stretched Pete 379 with 3 lift axles and huge dump

Customer Question

We have a stretched Pete 379 with 3 lift axles and huge dump body. After loading with 17 tons of gravel we noticed on an uneven roadway that the unit began to rock back and forth and was scary to operate on the interstate. We installed dual leveling valves on the air leaf suspension and raised the ride height in stages up to 2 inches over normal ride height. We still have the same problem. The truck did not do this a year ago with as much as a 25 ton load. We have run out of ideas. ??????
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  Michelle-Mod replied 1 year ago.
Hello,

I'm Michelle and I'm a moderator for this topic.

We have been working with our professionals to try to help you with your question. Sometimes it may take a bit of time to find the right fit.

I was checking to see if you had already found your answer or if you still needing assistance from one of our professionals?

Please let me know if you wish to continue waiting or if you would like for us to close your question.

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Customer: replied 1 year ago.


Still here pondering the vastness of the universe and wondering about Pete air rides

Expert:  Gina-Moderator replied 1 year ago.

Hello,

Thank you, XXXXX XXXXX continue to look for a professional to assist you. Please let me know if I can be of any further assistance while you wait.

Best,

Gina-Moderator

Expert:  spankyjr1 replied 1 year ago.
Hi and welcome Please do not rate until all your questions are answered that way you wont have to pay twice Use reply to expert link Thanks spanky

Sorry about your delay do you still want some assistance with this?

I know you installed duel leveling valves did you use one old and one new valve or what?

Do you have dash gauges installed that show how much air you have in each side?

Does this look like yours?



Have you ever weighed it to see if steer axle is getting overloaded?

Let me know Thanks spanky


x



Customer: replied 1 year ago.

We installed new "Barksdale" matching valves with internal dump capabilities. We do not have truck air bag pressure guages but the lift axles have individual pressure controls. For this load we have operated with 35 PSI on each lift axle, and at different truck ride heights, from 1" low to 1" above normal. The rocking motion is not constant but is concerning when it begins. The load stabilizes a small amount with the axles down but does not stop.


The vehicle has been axle load tested and meets the 12,000 lb. requirements for the steer axle and load parameters of all other axles.

Expert:  spankyjr1 replied 1 year ago.
Sorry about delay I went to sons baseball game and have to go to mother in laws for a hour so I will check back and be back the rest of the day.

The ride height that it calls for is the highest it should be, you can go a little lower to get a different ride,but up no more then 1/4" because it changes drive line angles to much, some owners say better some say worse.
The fact that it was good and then bad means something changed.

Do you have the part# XXXXX bark valves you installed?

The reason I'm asking is some modals have silicone in them to keep it from changing height all the time, they say for like, on uneven surfaces for short time it doesn't want to dump and fill constantly.
So the ones that do I take apart and dump about 1/2 of the liquid silicone out and makes it respond better.

When looking at your truck without a trailer on it does it have a slight downward angle from front to back?
Also from side to side?

When you adjusted ride height on each valve did you dump air all the way out of other side while making adjustment one side at a time?

Ride height should be changed at a rate of 1/8"-1/4" at a time until it suits your needs or feel.

We might need to talk back and forth a couple times until we figure this out so Please hold rating until were done.

I'm usually on line from 6am -6 pm

Let me know and I will check back within a hour.



x




Expert:  spankyjr1 replied 1 year ago.
I'm back so let me know when your ready.

spanky
Customer: replied 1 year ago.

Sorry, I apparently missed the send button at 4:15. I was at church from 4:30 till almost 7:30. We used either a pair of LV2358 or LV 2374 valves. We moved the left valve closer to the frame and mounted the right valve a proportional distance on the right frame rail with a shop built bracket.


We adjusted the ride height in 3/8-1/2 inch increments and test drove the vehicle after each adjustment. The vehicle was lower at the rear when it came in, but it is now higher (we will lower it again). The vehicle is level side to side. The vehicle was low enough to hit the u-bolts on the frame at times. The vehicle does not have towing capabilities. Even at the current height we have had no drive line vibration problems, just the side to side rock.


If you have felt a side to side rock as you leave a drive way or location and enter a road, you can imagine the slow movement. Now add that to a smooth looking road and 70 mph. You can't always see what causes the motion to start.

Expert:  spankyjr1 replied 1 year ago.
I know exactly what your talking about, I took a couple years off working on trucks for a injury and drove a Pete with 48' trailer, spread axle, with dump axle, hauling concrete pipe and re-bar steel, going in and out road construction sites and new home sights with roads that where only graded for getting us in/out.

On the slope of truck it should be sloped from rear to front. if you take a tape measure and measure frame height rear should be about 1" higher then front, just enough so you can see slope without using a tape measure.
That alone can make back end sway but not rock like you are saying.

If you need to change height of frame to achieve slope you shim under steer axle spring, they have 1/2" spacers under front springs and also a thin tapered shim that must be there and must go in the same way they came out,if you put in backwards your steering wheel will stick after a turn and slow to come back straight.

When you adjust ride height on valves start with no air in rear suspension at all on each side, then adjust one side, only going up until desired height is reached, if you go past height, dump air and start over.
This must be done separately, so after first side is done, dump air, then do second side, then dump air and let it level on it's own.

Valve distance to frame should be closest to frame without interference and you already said they are equal side to side.

Only the second part# XXXXX gave me comes up and it shows it's a hydraulic leveling valve with pressures between 3000psi-5000psi I don't know off hand if they also use them for air its not giving me the low side specs.
How long is the delay when you move lever before it starts to dump or fill using the lever not dump option?

Let me know after checking and adjusting Thanks spanky

spankyjr1, Journeyman
Satisfied Customers: 1850
Experience: I worked on all types of equipment semis,forklifts,farm,ect.
spankyjr1 and other Medium and Heavy Trucks Specialists are ready to help you
Customer: replied 1 year ago.

Thanks for the assist. Truck owner wants single valve put back and refuses to persue the problem. We could not put a finger exactly on the cure and the first effort failed so he lost confidence. We tried to get him to rebush and align rear but to no avail. Again, Thanks.

Expert:  spankyjr1 replied 1 year ago.
Your welcome.And Thank You for the positive rating.

Take care spanky

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