Suspension lop sided (4 bag)

[Hermjeji]

So, have a 2004 T800 dump truck with a neway 4 bag 46k suspension. It has only
One levelling valve, and was recently replaced to try and solve the symptoms I’ll describe below. Obviously it is not fixed yet.

When empty, the suspension appears straight (ie. on level ground)

As soon as there’s about 3-5 tonne of a load in there (13 tonne legal) you can see the passenger side does not want to inflate as much. It ends up at full load having about 3-5inches of drop
On the passenger side. The air bags don’t appear to be damaged, and they all are the same bag. No leaks at the bags.

Appreciate any experience you’ve had to sort these straight.

[JimT]

Not something I've dealt with before. But, you could try swapping the bags left and right. If the problem follows the bag then it's something with the bag itself, otherwise it's probably some other component.

On a side note, I had a Z spring break on a single axle daycab once. Seemed fine until I had the trailer jacked around a bit, then the broken side would drop so the trailer was hitting the tire. Straightened out and it'd ride normal. Point is, with enough weight on it the airbag wasn't able to compensate for the broke spring. Have you taken a close look at the springs? In my example the spring had cracked directly between the 2 u-bolts and was hard to spot until I went looking for it.

[Rawze]

(08-26-2021 )Hermjeji Wrote:  So, have a 2004 T800 dump truck with a neway 4 bag 46k suspension. It has only
One levelling valve, and was recently replaced to try and solve the symptoms I’ll describe below. Obviously it is not fixed yet.

When empty, the suspension appears straight (ie. on level ground)

As soon as there’s about 3-5 tonne of a load in there (13 tonne legal) you can see the passenger side does not want to inflate as much. It ends up at full load having about 3-5inches of drop
On the passenger side. The air bags don’t appear to be damaged, and they all are the same bag. No leaks at the bags.

Appreciate any experience you’ve had to sort these straight.

could be an air-flow issue, or also could be air bags worn out, hower ....
what you describe sounds a lot like the leaf springs/beams are going bad on the one side that drops the most.

[Hermjeji]

Wow - that much variance from weak leaf springs is a shock to me. I believe the bushings on one side are to a point where they are due for replacing as well, might as well do those together with the front spring. They haven't been replaced for 6 years and who knows how long since they had it before. It also hauled transfer before, so that's overloading front axles as well.

Will update accordingly. Thanks.

[Hermjeji]

Okay an update on this. Front springs replaced, shackle pin bushings, torque rod bushings, pivot bushing, and another re/re of the levelling valve. The problem is 90% solved. Ie. it works fine 90% of the time, but then sometimes, it still does things like this:


The problem is only when loaded, and there's no real pattern as to when it happens. This is a silo load of asphalt to, so about as even of a distribution you can get. The shop did say to bring it back if it continued to do it and they'd take care of it, but it's intermittent so, no luck with that.


-

[marek4792]

how are your airlines and bags, like Rawze said sounds like a flow issue? I almost wonder if it's the way the lines are ran. I would try T-ing off each axle and run one line to one port on the leveling valve. Like you would run a fuel line between the tanks to balance them out, but with air between the bags on the same axle?

[Chamberpains]

This may not be the suspension causing this.. could it be something in the bed mounting? Have to checked the pivot pins on the bed? What does the mounting bolts of the bed look like? It's possible to have a broken or severely worn out bolt or pin that only shows itself when in the perfect position to do so.

[Rawze]

If I owned a dump truck like that, would it not make sense to use a separate levelling valve for each side... just to compensate for possible uneven loads, and to help prevent a rollover when the bed was partially up?.

[trucklogger2]

loading from a silo like that the box fills super fast-dump your air before loading
then fill bags either after or during or shortly after they start loading second batch.
see if that helps