Lifton LS850 wont drive uphill

[CaptLimey]

2/4wd? Update

Advice from my resident Guru Jon confirms that the 'serial lines' are, as I suspected , fluid return lines that convey the liquid back to the pump after it has been through and driven the wheel motors in forward. For those that have access to the manual (and can be bothered) page 5-14 of the Travelling Drive section shows the flow schematic.

He also suggested that, although the front motors are not shown as having a separate reverse HP feed, the serial lines transfer the HP fluid from the rear to feed the front motors when in reverse motion. Therefore they are powered when in reverse. In effect the fluid flows in opposite directions in these 'serial lines' depending on which direction is selected by the operator.

Anyone have a different take on that?

Rgds CL

[Muz]

The backs are certainly powered because I can load mine in reverse when empty up a steep slope.

the motors are quite simple devices usually with bidirectional flow (2 lines) and an exhaust low pressure outlet.

given the pump is a single output...(possibly to each axle) It's flow will have to be diverted to each wheel equally, and its most probably this control device that has the problem. On top of that there must be some sort of anti slip control system that prevents a wheel with no grip spinning, and applies power to those that have grip. Then there will be a lock system that stops flow when the drive is in neutral.

[CaptLimey]

The backs are certainly powered because I can load mine in reverse when empty up a steep slope.

the motors are quite simple devices usually with bidirectional flow (2 lines) and an exhaust low pressure outlet.

given the pump is a single output...(possibly to each axle) It's flow will have to be diverted to each wheel equally, and its most probably this control device that has the problem. On top of that there must be some sort of anti slip control system that prevents a wheel with no grip spinning, and applies power to those that have grip. Then there will be a lock system that stops flow when the drive is in neutral.

Hi Muz and thanks for the info.

You're quite right, there is power to the front wheel motors in reverse, it comes from the rear wheel motors via the 'serial lines'. Don't know about any control/anti slip/neutral locking devices, haven't dug that deep yet.

You'll probably recall that our original problem was the inability to climb an incline and the tendancy for the front right wheel to 'lock'.
More by luck than judgement I've been able to 'tinker' with the 'Control Cartridge' adjustment on the R side of the pump and get smoother power delivery but the wheel locking and engine labouring problems persists. I swapped the 'serial lines' (or flow return hoses) between the left and right front wheel motors and found that the locking problem moved to the left wheel! It is more pronounced in forward than reverse. It suggests that the motors and pump are all doing what they should, that HP feed is good and we need to look at the flow return system. Work in progress!
Rgds CL

[CaptLimey]

Help! - from 'Confused' of southern France

Hi all
I've been trying to fathom out the problem with the flow of fluid that might cause the wheel locking and labouring problem on the right front wheel and thereby what needs replacing. The attached schematics demonstrate the flow line connections to the front and rear drive motors.
The front wheel motors have a forward high pressure supply and a connection via 'serial lines' to the rear wheel motors. These connections have a non-return valve in their circuit.
The rear wheel motors have a forward high pressure supply, a reverse high pressure supply and 'serial line' links to the front wheel motors via the same non-return valves. These valves are linked and connected to the HP pump.
As noted in my earlier post, when I swapped the front wheel motors from one side to the other the 'locking/labouring' problem persisted with the right wheel, suggesting that the motors were not at fault. When I swapped the 'serial lines' left to right and vice versa the problem moved to the left side. This suggests that the HP supply flow is OK but there's a problem in the 'serial line' circuit. But, without knowing the purpose and function of the non-return valves or in which direction they allow the fluid to flow, I'm at a loss to determine what to replace. Should it be the non return valves or the 'serial lines' or both? OR something else entirely
Any ideas/suggestions/explanations will be much appreciated.
Rgds CL

RearLinesWEB.jpgFrontLinesWEB.jpg

[Muz]

Logic would suggest the components that arent adjustable and get worked the most .. which in that circuit would be the motors , or the non return valves .. and youve eliminated the motors .. maybe pulling the valves apart might reveal something, either damage or a small bit of rubber getting trapped and preventing proper opening or closing, if pressure is leaking from the opposite circuit whilst the opposing service is called, it may affect pressure on that side. I cant remember where we are at, did you ever do a pressure test between each side ? I shall re read the thread when I get a mo

[Stock]

It would suggest you have a bleed back issue. you could eliminate the NRV by feeding the static/serial returns to the tank. or see if your local supplier has two in line ones an remove the dumper own ones.You might have a NRV leaving back under pressure, this pressure may even come from the pump itself.

[CaptLimey]

Stil a little 'Confused' of southern France

Logic would suggest the components that arent adjustable and get worked the most .. which in that circuit would be the motors , or the non return valves .. and youve eliminated the motors .. maybe pulling the valves apart might reveal something, either damage or a small bit of rubber getting trapped and preventing proper opening or closing, if pressure is leaking from the opposite circuit whilst the opposing service is called, it may affect pressure on that side. I cant remember where we are at, did you ever do a pressure test between each side ? I shall re read the thread when I get a mo

My heartfelt thanks go to both Muz and Stock for taking the time to educate this hydraulic neophyte!

To answer your query Muz, I've only tested the pressure on the pump output for the forward motors, just to confirm that it was achieving sufficient pressure. It was showing 310 bar, I've yet to test at each motor feed, perhaps that's another step down the logical clue path?

Thanks Stock for the coloured flow schematic, it goes towards helping me understand the system we have, although I'm still a little foggy about how the front motors are powered in reverse. The system on our Lifton doesn't have a separate reverse flow feed to the front motors. All motors have a forward motion HP feed from the pump, which I believe, is returned to the pump via the serial lines.(?) When reverse is selected the rear motors have a reverse HP feed from the pump but there is no reverse HP feed to the front motors. They appear to be fed reverse HP power through/from the rear motors via the 'serial lines'. At least that's what I interpret from my reading of the schematics I attached to my last post. Would you agree or am I misinterpreting the schematics?

However, if that is the case, then surely wouldn't the reverse HP feed to the front motors, assuming it travels via the serial lines, simply return to the pump through the NR valves before it gets to power the front motors?

Whatever the flow routing is, from what both of you suggest, the finger of suspicion is pointing to the NR valves and our next logical step should be to remove and examine each.
I haven't yet detached and disassembled either of the rear motors. Maybe that's the next step, if I can't find any fault with the NR valves?

Again many thanks for the advice and guidance - please keep it coming

Rgds CL

[Stock]

Can you email me them drawings please as I can't make out the detail even with the new glasses..........

From what I can make out it appears that there is no reverse drive to the front wheels
line 4?and 5? appear to be going in to bottom of the pump block, and lines 1? & 3? going to the top of the pump block.........

[Muz]

Or you could simply swap the NR Valves and see if the problem is replicated on the other side ?

[CaptLimey]

Can you email me them drawings please as I can't make out the detail even with the new glasses..........

From what I can make out it appears that there is no reverse drive to the front wheels
line 4?and 5? appear to be going in to bottom of the pump block, and lines 1? & 3? going to the top of the pump block.........

Hi Stock
No reverse drive to the front wheels? That's what I thought, hence my question in my post on 31/3/13.

I haven't jacked all wheels off the ground to try, I'll try that soon just to satisfy the question.

I'd email the drawings if I knew how to! I tried the site's email option to you but couldn't see anywhere to attach the images - guidance needed please Mr. Moderator.

However this link <http://www.globalplant.co.uk/PDF/Lifton%20Neuson%20Wacker%20850%20Dumper%20Parts.pd f> should get you the whole spare parts list PDF. Pages 57 and 58 are the originals.

I'll send you my email, please contact me direct if I can send anything more helpful to you.

Many thanks CL

[CaptLimey]

Or you could simply swap the NR Valves and see if the problem is replicated on the other side ?

Good idea Muz thanks, I'll add it to the list of things to try.

I had a chat with a Wacker Neuson mechanic who suggested I go back to basics and test the varios pressure outputs at the forward/reverse test points and the pilot pressure point. He added that 310 bar I got at the forward test point was a little low, if that was the maximum, as it should be 360 and may be the cause of the poor gradient climbing?
More stuff for the list of things to try! Oh well - keeps me off the streets.

Rgds CL

[CaptLimey]

Does the forward axle have drive in reverse? - yes it does - BUT!

Re my earlier post:-
I tried the 'all wheels off the deck' trick and found that, yes, all wheels are definately driven in reverse and forward. BUT on our machine the right side has considerable more precedence over the left side. Up to mid revs both in forward and reverse the right side wheels spin nicely while the left side remain stationary. It's not until I put the pedal to the metal do the left side wheels start to spin and even then not always! Although when I drive the machine up and down our lane all seems perfectly normal. Not knowing anything about the normal drive characteristics of hydraulic pumps and wheel motors I don't know if this is normal or not. Any suggestions?
I'll try to post a short video of this phenomenon if someone can please tell me how to attach a video to a post.

Rgds CL

[Stock]

These appear to be low pressure case drains






This hand Brake set up might need to be looked at as it fed oil from the pump off a different port




It appears to these tired old eyes that on the front motors you have forward port, reverse port, hand brake, and case return. Do you know which axle it is binding on?
Wonder if the pump is bleeding pressure on the hand brake circuit ??

Just another thought............they are the same as tracking hubs...so you have you have two feeds forward and reverse ........the case drain is the return .........and the third port on the front hub for the hand brake..........

[Muz]

Re my earlier post:-
I tried the 'all wheels off the deck' trick and found that, yes, all wheels are definately driven in reverse and forward. BUT on our machine the right side has considerable more precedence over the left side. Up to mid revs both in forward and reverse the right side wheels spin nicely while the left side remain stationary. It's not until I put the pedal to the metal do the left side wheels start to spin and even then not always! Although when I drive the machine up and down our lane all seems perfectly normal. Not knowing anything about the normal drive characteristics of hydraulic pumps and wheel motors I don't know if this is normal or not.

Its probably not a valid test here, because the pressure (should) get balanced to each corner when resistance is met, i.e. a load being applied/hauled.

If theyre off the ground the easiest side will turn first possibly due to (for example) it being fed first or even the difference of one or two bar in pressure due to other components in the circuit. Only measuring the pressure whilst chaining it to something solid and gunning it will tell you whats going on at each corner.

On your other point earlier on, about 310 Bar being a bit low ... thats what mine are running at and they are absolutely fine ... so thats not the problem ... I think those NRV's are due a tug, and inspection .. they should really be tested though, incase nothing visible shows its self, say one has a weak spring load for example ? (if thats how theyre made)

[Muz]

What Stock mentioned about the Hand Brake valve might be worth isolating too .. its a solenoid valve IIRC, but none of my 1 tonners have the handbrake .. the valve is controlled by a switch on the dash which is a park switch but it does the same job, Some older models (and my 3 tonner) had a handbrake, but it simply used a microswitch on the handbrake lever handle to operate the circuit .. that cost me a few bob from the dealer everytime the switch failed .. they allways justified the call out as a genuine fault .. It was only later I had a good look and realised the switch just seized every so often with dirt, so now a quick WD40 every 3 months and I havent had a call out since.

Anyway .. you could just connect the lines together to bypass the park valve to remove it from the circuit