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.

 

[dfkrug]

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.

Can't you just remove the PTO cover plate and fish in there with a magnet
wand? At least those parts are steel....you can't do that with aluminum.

 

[Brimstone10x]

Hey all . Ive been down this road a few times . Deere ofers a updated shaft for the hydro trans ,that uses a larger nut in place of the 3/8 bolt that has failed . Its been imposeble to remove the broken off bolt head and washer with a magnet. If you want to dismantal the trans axle you could remove them . We have just left them in there to save the labor costs and not had any issues. Its no an f1 car its a tractor . Just replace the bolt and washer and gear if needed and reinstall the hydro trans unit. It lasted this long do you need it to last another 20 years ? John.

 

[mfreund]

If it was my tractor I would want it to last another 40 yrs!!!

 

[MartyinPA]

Hey Folks,

My JD 955 started a similar symptom yesterday. When facing downhill the transmission "slips" accompanied by a high pitched whine. However, it goes uphill with no problems - no noise, no slipping.

First thing I did was check the fluid and it was way low. So I topped it off but the problem persists. No change. Uphill runs fine, down hill it just takes off and rolls.

Could this be the same problem with the bolt that he was having on his 855?

Any other thoughts?

Thanks,

Marty

 

[jd110]

Absolutely sounds like it. The gears is helical cut and it will drive under load in forward. Free wheels going down hill and will not back up.

 

[MartyinPA]

Does anyone have a set of instructions to get to that bolt, remove it, replace it, etc? I cannot get to my service manual (electronic copy on a crashed PC). Any pointers would be appreciated!