Woa!!!!

[thcri]

My sensi-trac has always kicked in when needed except for going down the hill. When I do go down the hill I do keep my foot on the hydro a bit but I still have to hit 4 wheel or it will tear it up pretty good. I watched my son drive down once and I notice the one wheel trying to back up while the other went forward. If I put it in 4 wheel then I am ok, now my slope is so steep I don't dare go sideways on it or I'm a history. If it is really dry then I am ok I can go down without 4 wheel. If I have the loader on I have to have it in 4 wheel.

Maybe I should give my dealer a call. I guess I just thought it to be normal with one wheel trying to go opposite. I have seen that so many times on other vehicles/tractors etc that I never thought much about it having something wrong.

murph

 

[jinman]

</font><font color="blue" class="small">( I watched my son drive down once and I notice the one wheel trying to back up while the other went forward. )</font>

Murph, I'm certainly not an expert on our differentials, but I'm wondering if your one wheel reversing might have something to do with your problems of getting the differential lock to release properly?

Also, if you've ever had a car jacked up in the rear with both wheels off the ground and the transmission in gear so the drivetrain won't move, you can rotate one wheel and the other one will rotate in reverse. If you are going downhill and your tractor is in low range on the hydro, it might be that the drivetrain can't turn easily so one wheel with the lowest traction will actually turn backwards. If traction was exactly equal, I bet both wheels would slip. If you put the transmission into a higher gear, the drivetrain will cause the hydro to attempt backpumping a little and let the drivetrain rotate so that both rear wheels can turn.

This is just a "gut" feeling based on what I've seen with drivetrains and realizing that it's almost impossible to make a hydro drivetrain backpump. That's why when you lift the pedal, the tractor stops on a dime without braking. What do you think? /forums/images/graemlins/confused.gif

 

[AndyG]

You folks have given some good info. I was wandering about stopping all 4 wheels using the brake pedal. From Murph's description it sounds like I need to lock 4wd in.

 

[kensfarm]

Doesn't the manuel recommend putting the tractor in 4wd lock when traversing steep slopes?

 

[JASTN70D]

I have witnessed the same phenomenon (wheels turning in opposite directions going down hill) on a JD hydro.

This seemed to only happen when there was major slippage on the tires. I think it is related to the differential more than anything to do with the hydro.

I have spun the rears on gear tractors while there jacked up and they also turn in opposite directions. I haven't noticed if they rotate in opposite directions while sliding down hill yet. Not something I would willing experiment with either. /forums/images/graemlins/tongue.gif /forums/images/graemlins/tongue.gif

 

[thcri]

Jinman,

I am thinking more just the differential. If I jack up the back of the tractor and push one wheel one direction the other goes the opposite direction. This may only happen during slippage when on the ground. I am planning on stopping at my dealers this week-end and see what he says about it. I remember when I test drove a TC18D when I was buying my 21 the dealer drove down a wet steep hill and had the same problem. One wheel looked like it was trying to go backwards and the dealer was trying to get the differential lock in, but he couldn't find it. I thought he was going to tip the tractor over.

As far as my differential lock. I have not dug into it yet but I am thinking the linkages just need a good lubing up. The tractor sits outside all summer and then inside in the winter. I have not used the differential lock in close to a year. So I am hoping it is more linkage related. I even kind of remember it was a pain to get it into lock. I had to step pretty hard.

murph

 

[rambler]

</font><font color="blue" class="small">( I have witnessed the same phenomenon (wheels turning in opposite directions going down hill) on a JD hydro.

This seemed to only happen when there was major slippage on the tires. I think it is related to the differential more than anything to do with the hydro.

I have spun the rears on gear tractors while there jacked up and they also turn in opposite directions. I haven't noticed if they rotate in opposite directions while sliding down hill yet. Not something I would willing experiment with either. /forums/images/graemlins/tongue.gif /forums/images/graemlins/tongue.gif )</font>

It's all about least resistance. One wheel spins backwards, the other wheel can spin 2x as fast & you go down the hill 2x as fast, for only one wheel slipping. The pull of gravity vs the resistance of the wheels - one wheel slipping 2x as fast backwards offers less resistance overall.

You realize going down the hill facing forward, your ag tire is actually working 'backwards', it is as if you had the wheels mounted the other way, with the tread facing wrong. It is real easy to lose traction that way.

--->Paul