Workmaster 105 No Fwd or Rev

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muttnjeff
TwoWaves
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Joined: Tue Jul 21, 2020 7:19 pm

Workmaster 105 No Fwd or Rev

Post by muttnjeff »

I’ll start by letting all know there are no waveforms with this post, however it was an interesting diagnostic case.

Machine was being worked on for some minor leaks on various hyd lines, fittings, etc. and routine service.

The tech had repaired the leaks, which included a leak on the power shuttle valve which allows for hyd control of the fwd and rev functions in addition to flow of the oil cooler and some lube supply functions internal to the transmission.

Post leak repair the tractor was no longer able to move fwd or rev, first check was the valves operating pressure and clutch pressures for fwd and rev. Test proved there was 240 psi in the valve and 40 psi in the clutches, spec calls for min. of 260 psi internal to the valve and clutches.

Tech removed valve to check gasket for alignment issues, missing port, etc., no issues with gasket so a new valve was ordered as the was a concern the torque patter and specs were not followed.

New valve and gasket fitted, no change. Next step was to go back to the hyd schematic and verify what was in the path between main hyd pump and shuttle control valve.

Basic flow path is trans housing is sump to the main hyd filter to the engine driven dual psi pump to the steering motor to the steering motor return filter which supplies the shuttle valve and pto control valve.

Since the shuttle valve pressure was down 20 psi (at least) it was decided to remove the steering filter, retest and had an increase of 20 psi.

Interesting change so gauges were moved to the next check at the engine driven main hyd pump.

Spec for pump is min 2500 psi at 2300 rpm and min 2700 psi at 2300 rpm for the low and high pressure sides.

After getting correct fittings and gauges test one hade the pressures at 2300 rpm as follows low is 700 psi and high 500 psi.

Then a new main hyd filter was fitted and a gain of 50 psi ( generous estimate) was gained in the low and high however the pump was still significantly below spec. Final repair was the verification of the suction line being clear of obstructions and replacement of the pump.

The question on everyone’s mind is how can a tractor be functioning as it should, since the machine was driven into the shop, also what did “opening” the system up cause or create that led to this interesting diagnostic case.

Thanks for reading..

ben.martins
Pico Staff Member
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Joined: Tue May 16, 2017 1:02 pm

Re: Workmaster 105 No Fwd or Rev

Post by ben.martins »

Interesting read muttnjeff, thanks for sharing!

Opening up a hydraulic system is always risky especially with the potential for contamination ingress from the working area, air entering the system requiring bleeding as well as new hoses containing contamination.

Cleaning the pipes before fitting was something I never gave much thought to prior to starting my hydraulic journey with Pico but spending some time with the professionals has meant whenever getting a new hose made up I ensure it is 'cleaned' prior to fitting. This usually involves a foam pellet being fired through the hose to clean out any deposits ensuring the new pipe doesn't fill my system with dirt!

Sorry slight tangent there but the quest for cleanliness around hydraulics cannot be overlooked.

Whilst the repair in this instance sadly ended up being a replacement pump, I feel like there is a little more to the story! I look forward to reading more.

Thanks again.

Kind regards

Ben

muttnjeff
TwoWaves
TwoWaves
Posts: 60
Joined: Tue Jul 21, 2020 7:19 pm

Re: Workmaster 105 No Fwd or Rev

Post by muttnjeff »

Wanted to update the post with the resolution…

New pump was replaced in error, incorrect test procedure, final fix was a bolt torque being to high on a certain area of the valve, all bolts torqued to 66ftlbs with the exception of one that resides near the main regulation piston which affects the flow into the circuit for the forward and reverse clutches.

The bolt torque, recommended by engineering torqued to half the specification of the other bolts torque, this is all new information that was not in the service information and will be corrected for future reference.

Thanks for reading..

ben.martins
Pico Staff Member
Pico Staff Member
Posts: 317
Joined: Tue May 16, 2017 1:02 pm

Re: Workmaster 105 No Fwd or Rev

Post by ben.martins »

Thanks for the update Muttnjeff and just goes to show how something relatively simple as this can send you off down a rabbit hole. This one was definitely never going to be an easy find though!

Thanks for sharing!

Kind regards

Ben

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