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Very Weak "drive" Hydraulics


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#1 ENafziger OFFLINE  

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Posted July 07, 2014 - 11:40 AM

Machine is a Snapper 1855A with 591 hours on it.  I have been having increasing trouble making it "go" lately.  In high range, it will only pull itself along on flat ground or downhill.  Going uphill it gets slower and slower, and requesting a faster speed with the hydro pedal just makes it worse.  You have to back off the pedal and just barely ease into it to get the machine to go.  As such, I've been using the machine in low range to get by for now.  However, it's started doing the same thing in low range.  With any weight in tow, it struggles to go up any incline.  Also, the rear 3pth is weak, and will not lift the bushhog at all.

 

I've heard that if these machines are hooked to a heavy object, that they should spin both back tires until they bury up in the ground.  This is defnitely not how mine behaves.  I have never been able to get a tire to spin even in loose ground.

 

The fluid level is up on the hydraulics, fluid is pretty clean, the splines are not stripped on the hydraulic input, etc.  I'm mostly convinced it's something internal.  Does anyone have any ideas?  Any help would most definitely be appreciated.

 

I have 3 of these 1855s that are somewhat driveable.  This one is by far the worst, but the other two are having "pre-symptoms" as well concerning weak hydraulics.  I need these to be able to work as intended, and so I'm committed to tearing in to them to fix as needed.

 

Thanks, Eric


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#2 ENafziger OFFLINE  

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Posted July 07, 2014 - 11:49 AM

Just for reference, here's the tractor I'm talking about.  The bushhog is only off the ground slightly because I lifted it manually.  The 3pth cylinder will not pick it up like this.

 

WP_20140703_15_27_00_Pro.jpg

WP_20140703_15_27_12_Pro.jpg

WP_20140703_15_27_31_Pro.jpg

 

--Eric


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#3 gtcsreg OFFLINE  

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Posted July 07, 2014 - 11:57 AM

I'm not your expert but sure sounds like internal.  I've experienced this on a sealed transaxle.  Gave the tractor to my brother and he sold it as is.  So I don't know much but you have my sympathy.


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#4 Bill 76 OFFLINE  

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Posted July 07, 2014 - 06:25 PM

Don't know anything that model but is there a filter on it that could be plugged,or a pressure relieaf that is on the fritz---

just tossing out ideas.



#5 olcowhand OFFLINE  

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Posted July 07, 2014 - 06:34 PM

The first thing to look at are the belts that drive the hydro.  Many times they are the only issue.  One way to know for sure if they are slipping is to use a photo-tachometer.  Test the speed of the engine & hydro at the same time and their speeds should match exactly.  If they don't, then they are slipping.  Rule this out first.


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#6 JDBrian OFFLINE  

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Posted July 07, 2014 - 07:08 PM

With only 591 hrs that hydro should be in good shape if it wasn't abused. Do those tractors have a bypass valve for moving them when not under power? Perhaps that isn't closed all the way. 


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#7 olcowhand OFFLINE  

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Posted July 07, 2014 - 08:47 PM

With only 591 hrs that hydro should be in good shape if it wasn't abused. Do those tractors have a bypass valve for moving them when not under power? Perhaps that isn't closed all the way. 

 

No bypass, as the rear end has a Hi/neutral/Lo shift.


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#8 Chopperhed OFFLINE  

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Posted July 07, 2014 - 09:49 PM

Look for belt/ driveline slippage first.

If that's ok. then next thing would be checking pressures.

 

I, personally, suspect a leaky bypass or relief valve or something similar.


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#9 ENafziger OFFLINE  

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Posted July 08, 2014 - 11:02 AM

The first thing to look at are the belts that drive the hydro.  Many times they are the only issue.  One way to know for sure if they are slipping is to use a photo-tachometer.  Test the speed of the engine & hydro at the same time and their speeds should match exactly.  If they don't, then they are slipping.  Rule this out first.

 

Well, thanks Olcowhand.  I pulled the center plastic cover in front of the seat, so I could see both the rear pto shaft (engine speed) and the shaft to the hydraulic pump below it.  Since the problem only occurred while under load, I put a piece of reflective tape on each shaft where I could shoot it with the tach while driving.  Both shafts were the same speed at idle.  Driving normally on flat ground, they were within 50 rpm of each other.  Starting up a slight hill...the engine speed was 2,400 rpm and the hydraulic pump speed was 600 rpm.  This was definitely the problem.  I'm both relieved, as well as feeling a little sheepish for not catching that.

 

The odd thing, is both drive belts look good.  I had inspected them, and the tension when the problem started.  Can belts simply loose their "slipperiness" or ability to grip the pulleys, even though the belts visually seem ok and the tension is set right?

 

At any rate, thanks again for the help guys.  Glad it turned out to be so simple.  I'll put on a new set of belts tonight!

 

--Eric


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#10 olcowhand OFFLINE  

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Posted July 08, 2014 - 11:17 AM

I figured it was slippage, and relieved for you that's all it turned out to be.  Those photo-tachs are awesome!


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#11 olcowhand OFFLINE  

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Posted July 08, 2014 - 11:19 AM

Oh, and look at the pulleys closely for wear at the belt grip area.  I've seen them grooved out to where the belt can't grip right.  But an old dried out belt sometimes slips no matter how tight.  And if the bottom of the belt has bottomed in the pulley, you can't tighten the belt enough to stop the slip!


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#12 coldone OFFLINE  

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Posted July 08, 2014 - 07:45 PM

Also they must be the right belt. I tried using regular 4L belts on mine and they lasted 1 plowing. The belts on these have the "classic" profile not the fractional HP/fan belt profile.


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#13 ENafziger OFFLINE  

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Posted July 09, 2014 - 09:53 AM

Also they must be the right belt. I tried using regular 4L belts on mine and they lasted 1 plowing. The belts on these have the "classic" profile not the fractional HP/fan belt profile.

 

Hmm, interesting.  I'm not sure I even know the difference.  Thanks!



#14 JDBrian OFFLINE  

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Posted July 09, 2014 - 11:09 AM

Make sure the pulleys aren't slipping on the shafts as well. It's probably not the issue but is worth checking while you're in there.



#15 ENafziger OFFLINE  

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Posted July 21, 2014 - 09:29 AM

Well, the properly adjusted new belts did the trick.  It pulls now!!!! Saturday, I dropped a sizeable pine that needed to come down.  I cut it into two pieces and drug it up to split into campfire wood.  The old 1855 pulled and pulled and kept on pulling!  I had the middlebuster plow on it already from making furrows...turned out not to matter.  The tractor pulled the log and furrowed at the same time :)

 

WP_20140719_008.jpg

 

WP_20140719_020.jpg

 

--Eric


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