944E-42 Lull steering scenario

[joelmartin]

Operator of 944E-42 says he always leaves it in 4 wheel steering mode, but at random the rear wheels will drift to the right or the left.
Anybody experienced this before?:beatsme:Banghead

 

[barklee]

Totally shooting from the hip.... but it sounds like the steering mode selector valve is by-passing?...?
I have never had any of ours do that though.

 

[joelmartin]

Well I was suspicious of the same. Dismantled it, cleaned it, looked for porosity, cracks, seals o-rings etc, could not see any reason for it to bypass. Only question I had was there is what looks like a tiny bleed off check valve type thing, I could not get air or brake cleaner to pass thru it in either direction.

If not that (new one is close to 600 bucks) Could the rear steering cylinder be seeping by, and if so, how could a person isolate that?
I suppose I could plumb the lines to eliminate the selector valve in the dash, to isolate that possibility.
Thanks much.

 

[willie59]

I'm thinking it wouldn't be the selector valve as you described problem was in rear steer only when in 4 wheel steer mode. I would think if selector was faulty, it would affect front as well in 4 steer mode. Problem could possibly be piston seal bad in rear steer cylinder, seems that would better explain how front remains steady and rear drifts.

 

[Speedpup]

I have a 1044B Lull that has done that since 1992 when I got it. Worse when cold. I think it is the selector valve and they are 6-700 for mine. I got so use to it I just correct it on the fly by going to front steer only for a blip.

 

[joelmartin]

Hello again. A different 944 this time, same problem.
We replaced the steering selector valve and it still goes wacky.
Someone suggested that even the front cylinder could be defective and it seems like the rear because the rear does exactly what it is told to, while the front is lagging behind, trying to play catch-up, and so you are busy turning the steering wheel and watching the fronts, while the back wheels are fine.
Any who, we did some pressure testing on our own volition. I am unsure what the inside of the front cylinder looks like, but the following is what we found:

Lull 944E-42
S/N 0160008264
According to the following pressure readings, I am making an educated guess that the front steering cylinder is bypassing
I teed into the left side of the front steering cylinder
Pressures as follows:
Holding steering wheel all the way to the right, at idle, it will build pressure to 1,500 psi
Holding steering wheel all the way to the left, at idle: 1,100 psi

I then capped the cylinder fitting, & plugged the tee, to deadhead.
Steering right, deadheaded: 2,200 psi
Steering left, deadheaded: Big Fat 0 psi, nada, zilch , nothing

Compare to the right side, just for kicks:
Teed in, steering right: 2,600 psi
Steering left 0 psi

Capped, plugged, deadheaded, steering right 2,600 psi
Steering left: 0 psi

Or am I missing something here?
Let us get a good educational discussion going here, I am eager to collect all the info I can. Information is power. Thanks.

 

[joelmartin]

JLG says there has got to be something wrong in the cylinder so I took it to hydraulic shop so they can test it and everything.
Will inform

 

[joelmartin]

The hydraulic shop found no obvious reason for it to be bypassing, so they installed a kit anyways
I put it back on the machine yesterday,
Teed into the line exactly where I did previously, where it showed a bypass condition
Now the pressure went up to 2,100 instead of only 1,500, and zero, in the other direction
Could be my imagination, but it seemed to me that the steering is almost effortless,
and very responsive compared to before, which makes sense, if it was not sealing correctly.
Time will tell if there is yet another defect…….
Your input please..

 

[18nascar18]

Joelmartin, it is usually always the steer cylinders causing the machine to track funny in the 4-wheel steer mode. For future reference test all four cylinders(or two if thats all it has) because when we operate the machine we automatically put the front wheels in line with what we think is straight. Thus, you don't truly know which ones are faulty just by operation. If you can afford it, it is a good idea to re-seal all four cylinders at the same time so they don't fight against themselves making the steering not as smooth as it could be. Thanks, this is my first time to post, I enjoy making my living working on telehandlers and thought I should share my experience. I hope it made sense!