RK55 HST slipping probelm

[Littlegrey20]

Good evening all,
Sorry for the wall of text but I know having more information is helpful most of the time.

I have a RK55 that's developed an interesting probelm. Started around 30 hours, with the backhoe still attached I experienced a bit if slipping when going forward uphill but could turn around and back up the hill no problem.
Talked with the guys at RK and they suggested changing the filters, which I did and it didn't make any difference. Took the tractor back to them and they kept it for a while and felt they had solved the problem. Changed out a valve on the wet lines.
Once I had the tractor back home I took the backhoe off and all was well.
I plowed the garden with it, bush hogged several times and never had a problem until I hooked the backhoe back up.
I was demoing an old house and there's a fairly steep hill going up to it. I made several trips up and down the hill then the problem returned. I couldn't pull the hill without the tractor lunging. The engine speed stays the same but the tractor just loses momentum.
I figured it's the backhoe that's causing my woes so I unhooked it and continued on without it. Problem was still there just not as severe.

Let the tractor sit for a week and did the 50 hour maintenance then hopped back on to do some more bush hogging and it was running fine.
Another week goes by and it starts the same problem back up. I decided to try keeping the engine below 1500 rpm and see how it did and I had absolutely no problems. I kept it this way for the majority of the day as I was clearing brush but by the end of the day even with the rpms pinned to 1500 it started back.
I'm planning on taking it back to Rural King but would like to know what's going on incase it's something I can fix here at home.
First HST tractor but not my first tractor over all.

Thanks!

 

[oldnslo]

Does this tractor have front wheel assist? If yes does it operate the same in both two wheel and four wheel drive?

curious if possible there is a tire slipping on a rim causing this random problem

 

[Littlegrey20]

Does this tractor have front wheel assist? If yes does it operate the same in both two wheel and four wheel drive?

curious if possible there is a tire slipping on a rim causing this random problem

It does have four wheel drive and the rear tires are filled but it's not slipping on the rim. It does this in both two and four wheel drive.

 

[Deere Dude]

Are the RPMs 2000+ when this happens. What gear (low-medium-high) are you in when this happens.

 

[Littlegrey20]

Are the RPMs 2000+ when this happens. What gear (low-medium-high) are you in when this happens.

It does it in all gears.

 

[oldnslo]

Little grey,
You state the engine speed does not change when this problem occurs but does it sound like the engine is working harder or really no change in sound either?

do you hear any different sounds when this happens?

 

[Littlegrey20]

Little grey,
You state the engine speed does not change when this problem occurs but does it sound like the engine is working harder or really no change in sound either?

do you hear any different sounds when this happens?

There isn't any noticeable difference in the engine noise. If i have the auto throttle button turned on the engine free revs after hitting 17-1800 rpm.

The only noise that does happen is a whining noise that's similar to when you bog the tractor down in too high of a gear. Sounds like a hydraulic noise instead of engine noise.

 

[CH4Ohio]

It does it in all gears.

Just to confirm . . . You say that it does this in Low RANGE and Medium RANGE too? Your RANGE selection doesn't change anything?

 

[rgr33]

Is it possible you are operating in too high a gear for the work you are doing?

 

[5030]

if I'm not mistaken you can turn up the fluid pressure to the hydro but you'll need a shop manual for the correct values.

 

[oldnslo]

Based on the random slipping or surging I would check the charge pressure while this is occurring. The HST is a closed loop system where the work ports of the pump are connected directly to the work ports on the motor. The charge is to keep this loop full and under some preset minimum pressure. Loss of charge pressure would allow oil to escape this loop from leakage and allow the tractor to stop moving or move erratically but I would also expect some cavitation noise if this is happening.

Very rare that a system relief would randomly change pressures and they would only affect one direction of travel not both while charge have equal affect on both directions.

 

[TractorGuy]

My first thought is you should never drive any 4WD, HST tractor up a hill in anything other than 4WD low. Doing so has probably damaged something.

If it's still under warranty you might sweet talk them into running the necessary pressure tests to diagnose the problem and fix it. If you tell them you went up a hill in 2WD medium they will probably flag it as user error.

 

[5030]

One sustaining issue with the RK tractors is, Rural King outlets are ill equipped to troubleshoot any issues except minor ones. Why I'd never consider one.

 

[oldnslo]

My first thought is you should never drive any 4WD, HST tractor up a hill in anything other than 4WD low. Doing so has probably damaged something.

If it's still under warranty you might sweet talk them into running the necessary pressure tests to diagnose the problem and fix it. If you tell them you went up a hill in 2WD medium they will probably flag it as user error.

Would you care to explain why you must be in 4WD and low range and what would be damaged if you do not do this. This inquiring mind would like to know...

 

[TractorGuy]

Would you care to explain why you must be in 4WD and low range and what would be damaged if you do not do this. This inquiring mind would like to know...

Just common sense. Low range is for operating under heavy loads such as driving up a hill with a backhoe fitted. 4WD increases traction. 4WD will be most valuable coming back down the hill.

It may go up a hill in mid range but doing so will place more stress on the components. If that were not the case the tractor would not be fitted with 3 ranges to begin with.

Slope instructions from the manual:

4WD Use

 

[Sportsman762]

Tractorguy, that is for starting off on a steep slope. If you use a higher range the tractor will not move as the transmission bypasses. Unless you just sit there with the hydro not moving and the pedal mashed your most likely not going to mess much up. I learned how to use differential braking due to the front on tractors being too light to steer when going up the hills were I grew up.
Steep Hill has a different connotation depending on where you live. Steep in FL is different than OH, and much different than MT.

I am really curious what the OP finds out about their tractor. Seems really odd to have this problem with as low of hours as they have. I would be very suprised if they damaged the tractor. Due to the age I am guessing factory defect.

 

[Littlegrey20]

Tractorguy, that is for starting off on a steep slope. If you use a higher range the tractor will not move as the transmission bypasses. Unless you just sit there with the hydro not moving and the pedal mashed your most likely not going to mess much up. I learned how to use differential braking due to the front on tractors being too light to steer when going up the hills were I grew up.
Steep Hill has a different connotation depending on where you live. Steep in FL is different than OH, and much different than MT.

I am really curious what the OP finds out about their tractor. Seems really odd to have this problem with as low of hours as they have. I would be very suprised if they damaged the tractor. Due to the age I am guessing factory defect.

That's what I'm assuming as well. I've babied this thing since I bought it brand new.
Also, I've heard of starting on a hill in low range but not keeping it in low range for any incline. The engine doesn't bog when going up the hills when it's not slipping.
I spoke with the mechanic at RK and he feels there's a problem in the hydrostatic pump. I assumed a seal bypassing, picking up air since I have checked the fluid and it would have more air bubbles than it should have after an episode of jerking.

 

[Littlegrey20]

Just to confirm . . . You say that it does this in Low RANGE and Medium RANGE too? Your RANGE selection doesn't change anything?

It will do it in all ranges. Does it worse in low than medium and high though. Assuming this is due to engine rpm vs speed of the tractor.

 

[5030]

I still think it's the fluid pressure in the transmission. Pressure controls clutch pack clamping pressure.

 

[ptsg]

I still think it's the fluid pressure in the transmission. Pressure controls clutch pack clamping pressure.

What clutch pack? It's an hydrostatic transmission.