JD 855 transmission slipping

[kimodc]

Hello,
My tractor wont move! When depressing the pedals all i get is the sound of gears slipping. The sound seems like it is coming from the transmission, but it is hard to pinpoint exactly. It will move a few feet then just 'slips.' The charge pump seems to be working fine as I have power steering and the 3pt arms will still lift.
Has anybody had any similar experiences? Any advice would be appreciated before I start 'taking things apart'.

Thanks,
Kim

 

[kennyd]

Just a few thoughts:

1. The "charge pump" is integral to the HST and does not run the steering, 3PH or the loader. There is a separate pump for these called a "implement" pump and it's usually mounted directly to the engine but use use the same fluid supply (sump) as the HST.

2. Seems obvious, but is the fluid full and clean? When was the last service? The suction screen could be clogged starving the pump for oil...

3. Is the range shifter moving freely? You mentioned the sound of gears so I wonder if the lever is not moving enough to fully engage the gears to the HST. Try lubrication the pivot points of the lever and linkages...

 

[kimodc]

Kenny,
Thanks for the reply...The range shifter is moving freely and makes a solid shift in to Hi/Lo range, so I know that is not it. I just changed the HST filter and oil so that is not either. I suppose it could be a problem with the charge pump not developing pressure. The tractor will start off and go about 2 feet and then starts slipping. Any ideas as to how I could see if the charge pump was pumping?

I did notice that when I jack the back of the tractor off the ground and spin the wheels by hand that I get the same gear slipping noise.

I might start by taking the transmission out and inspecting...the tech manual doesn't make it sound too difficult.

 

[northernjake]

Hi Kim,
Does it by chance have a lever that you would disengage if you needed to tow or push it? If so, it may have got bumped partially by accident.
Good luck,
Jake

 

[UP855]

there is a nut that falls off on the hydrostatic pumps output shaft that holds a gear on stays on going forward comes off shaft going backwards or viceversa

 

[kimodc]

I know what you are talking about...was up studying the tech manual late last night. That was where I was thinking of looking first. Thanks for the tip!

 

[dfkrug]

there is a nut that falls off on the hydrostatic pumps output shaft that holds a gear on stays on going forward comes off shaft going backwards or viceversa

Do you mean the bolt (item 60) comes off? That would be bad. The good
news is the HST comes out easier than most other tractors since there is
a full frame.

 

[UP855]

yup 60 would be the culprit, I believe they made a update to the shaft part #15? that now has a stud sticking out of it and it takes a nut with a cotter key, I think that is how mine is set up
P.S. my hydrostat is sitting on the bench at work awaiting parts

 

[kimodc]

my diagram shows a stud sticking out of the transmission with the castle nut and cotter pin as well.

Why is your hydrostat on the bench...same issue?

 

[kimodc]

Sure enough! Took transmission out and the gear fell off in my hand. Now the BIG QUESTION IS...do I need to fish the broken bolt head and washer out of the transaxle? If so this would involve splitting the tractor to get the front face plate off the transaxle.