Go Bottom855 Tranny Problems
 | coachconverter
Join Date: Jul 2003 Posts: 3 Virginia 
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2002-02-15 35618
First off, I'm a bit of a novice on hydraulics.
I bought a 855 last year with about 1600 hours. I noticed while driving it home, not too far, that sometimes the tractor would slowdown and the engine appeared to Bog down. The engine sounds stressed and the tractor slows down.
After replacing all fluids, filters and a gerneral tuneup, the problem almost completely disappeared.
Now, after sitting through the winter, I go to use it and the problem is back but much worse. Going forward only, the tractor bogs down to a point that it stalls out, especially if I'm turning the wheel or if I'm on any kind of grade. I changed the fuel, fuel filter and added Hyd. fluid, but the problem remains.
I'm not above replacing all the fluids again, but does this sound like another kind of problem? The tractor is usable as-is, but I know it's straining the engine.
Any thoughts? Suggestion?
Thanks
Todd
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 | Murf
Join Date: Dec 1999 Posts: 7249 Toronto Area, Ontario, Canada 
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2002-02-15 35619
First of all, a really basic question, is this a Hydrostatic transmission? If it is I would be looking at the system pressure relief valves, and or the bypass valves. Best of luck. ....
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| coachconverter
Join Date: Jul 2003 Posts: 3 Virginia
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2002-02-15 35623
Sorry, yes it is hydrostatic. Your suggestion makes sense, if I understand it correctly. The Bog Down feeling I get, does feel like a pressure overload.
Are these valves something that wear out or clog up?
Thanks
Todd ....
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| jd110_1963
Join Date: Feb 2002 Posts: 87 westminster, md
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2002-02-15 35636
Todd, the first thing I would check is to see if the brakes are dragging. On a smooth, level surface, unlock the parking brake and place the hi-low range lever in neutral. The tractor should now roll very easily by hand. The range lever is located under your right hand leg just under the seat. If the tractor rolls easily, you may indeed have a transmission problem. If it does not roll easily, I would jack up the tractor one wheel at a time and see if there is more drag on one wheel or another. It could be something as simple as the brake linkage out of adjustment. Also is the tractor four wheel drive? if so is the problem worse with front wheels engaged? If it binds excessively with front wheels engaged, you could have mismatched tire sizes. Kenny ....
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| Dana Trumpp
Join Date: Posts: 1
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2002-02-15 35639
You changed the fuel filter, there are two, the other in in the tank. might be worth the time to check it. Once I had a similar problem with a 855. filter in the tank was pluged. Good luck ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2002-02-16 35649
If the 3ph is fully raised and out of adjustment, or locked down, then the 3ph may stay in lift mode. The relief valve would open and a 'scream' could be heard. Under such conditions, the hydraulic system would be demanding a lot of HP and the governor would fully open the throttle. The engine would seem to labour and may not have power to sustain speed in road gear or on hills. Prolonged operation would over-heat the hydraulic oil.
Anyway, it's a possibility, and an easier one to remedy than the other also good suggestions.
....
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 | Peters
Join Date: Feb 2002 Posts: 3034 Northern AL
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2002-02-16 35654
As the oil for the drive is passing through the oil filter I might change the hydraulic oil filters again? Check that the breather tube is clear as hydralic transmissions will do strange things if the expansion is not compensated. A little water in the tranny with a plugged tube could give some strange effects including emmulsification of the oil and clogging of the filter.
Has the transmission lost any oil after use? ....
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| todd R Reid
Join Date: Posts: 1
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2002-02-16 35655
Thanks to everyone for the suggestions. I got it figured out today. The brakes were stuck...oh well, at least it was an easy fix.
Thanks again,
Todd ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2002-02-17 35662
Todd: Happy the problem was a simple fix. In response to your relief valve question. Relief valves are spring-loaded ball valves that open when pressure overcomes the spring. As such, they are pretty reliable things, and since they are safety devices, they'd better be reliable.
I haven't heard of one sticking closed, but it's not uncommon for a spring to break and then the valve won't hold pressure. Springs also can occasionally weaken and require the valve to be adjusted by placing shims behind the spring. The results of such failures would be the opposite of your problem. The engine wouldn't labour because the hydraulics wouldn't work under any appreciable load. There are relief valves in the hydraulic high-pressure line, the 3ph, and most SCV's as well as HST's and power steering.
There also are check valves here and there that prevent backflow that may cause loads to drop in event of ruptured lines or pump failures. Again, these are very reliable devices. There usually are no check valves in lines from the SCV to loader cylinders, and ruptured lines do cause loaded buckets to crash.
....
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