Gradall 534D slow in 2wd

I have been working with a 534D9 the last few weeks, and I can honestly say I am quite frustrated by it. The road speed is unbearably slow. I build and install handrails, and have to run all over town. It's all close enough, and I cannot afford to have this thing hauled every time I change sites, but this thing only does 6mph. It did have a bad 4x4 switch, which I replaced, and I can now hear the 4x4 solenoid valve clicking, but it still won't go any faster.
It's my understanding that 2wd is only the front axle on these, so I tested against the parking brake. It spun a rear tire in 2wd, then I tried it in 4x4 and it overpowered the parking brake while spinning a bit more aggressively.
Is there a chance it has a defective selector valve, something plumbed wrong or??? Having this thing do 16-18 instead of 6 would make me and a lot of drivers a bit happier.

Does it have the traction lock pedal on the floor, somtimes they can get stuck on/down and that will really slow the machine down.

I pushed down and pulled up on that a few times, but didn't notice any changes. Shouldn't I hear a valve click with that pedal?

With it running I dont think you hear anything. If the pedal releases on it own its probably fine, I'm not sure if it affects it in 2wd anyway.

How does it run the rest of the time, does it rev-out.

Is it turbo'd? I have seen broken waste gate mounts because someone decided to use it as a step.

Just passing on thing I have run across before.

This unit is NA, so no turbo issues. It seems to rev out, but it's hard to tell with a hydraulic system. At WOT max speed, there is constant light black smoke, while if I back off just a bit it goes away. It sounds to be running at 2400-2600rpm.
I'll have to check the foot switch a bit when I get a chance. I have been looking over a rental unit of the same model being used by another contractor, it's embarrassing since that one will pass mine like it's standing still.

Hi 4x4_Welder,
These machines don't have a simple hyd drive system, you really should download the parts/service manuals from the JLG website to help you out.

http://www.jlg.com/en-US/Home.html

Click on Services in the left column
Click on Aftermarket Parts in the left column
Clink on link at right of page for Service/Parts/Operator Manuals
Click the link for Gradall
Click the link for Gradall Telehandlers
Select your model

It sounds like you might have a problem with the inching valve, can't say for sure though. The inching valve, which is actuated by the brake pedal, will cause the machine to drive at a slow/controlled speed even with the engine at a high rpm. Of course, this probably isn't the only thing that can cause your problem, but it's something to look at.

Thanks for posting that, I hadn't been able to find a manual so a my diagnostics were limited. I had questioned the inching valve a little since the brake pedal cut the drive as soon as it was pressed, and then the service brakes engaged at about half travel. This isn't right by the manual, so I'll have to see if someone screwed with the adjustment. I haven't had a chance to test the traction lock pedal yet either, I've been pretty busy making the stuff I need to install later on-

Well, I fixed it some. The foot switch is stuck closed, so I unplugged it. It now does about 10-12mph. The inch function works now as well. It has a lot of room for improvement, but now it doesn't take me half an hour to cross town.

4x4_Welder said:

It has a lot of room for improvement, but now it doesn't take me half an hour to cross town.

Click to expand...

Hey cool, now drivers behind you won't recognise you and cuss you because you not as slow "that other fool on a forklift that drives so slow"!

As an update- Something popped free in the drive system yesterday and now it does full speed Don't know, don't care anymore. This thing is a poorly maintained overpriced pile. The guy wants $19,500 for it, the local rental company has one for $14,900 that's in much better shape.
It also started running fluid out of the boom intermittently, and the lift cylinder rod is pitted with a pretty good leak.

Just goes to show that if you don't put any value in maintenance, pretty soon your equipment won't have any value either.