paccorti
Gold Member
- Joined
- May 21, 2000
- Messages
- 481
- Tractor
- TC35D with 16LA Loader
As I was driving my tractor around recently I started hearing a weird sound. I'll freely admit I'm not an expert on tractor sounds. In fact it took me a while to get used to the hydro "moans" and other sounds. This sound is very different. It is clearly a mechanical sound (my best guess would be the sound of a bearing going bad). The sound is intermittent, it does NOT always occur. However once it starts it continues for quite some time. There is no one thing I can do that will produce the sound. All I am sure of is the sound only occurs when the tractor is moving. If the sound occurs (and it only occurs while moving) stopping the tractor will stop the sound. I might add the sound occurs even if the tractor is on level gound and not under any load (not pushing or pulling anything... just moving itself).
The tests I've tried:
1. Tried applying brakes (locked together) while driving - no weird sound occured
2. Sound occurs in high or low range
3. Stopping tractor immediatly stops the sound
4. The sound definitely happens going forward; not sure about reverse
5. PTO can be on or off and the sound occurs
6. Sound occurs in 2wd (have not tried 4wd)
7. Steering angle does not seem to affect the sound (going straight or sharp turns, sound continues)
The dealer has offered to send someone out to have a look. I appreciate this. I'm having them hold off for just a bit. I'd like to have something more concrete to tell them than, "It makes a weird sound while moving sometimes." Additional tests I want to try.
8. Does pressing the hydro pedal harder/softer affect the tone of the sound?
9. Does increasing/decreasing engine RPM affect the tone?
10. Try sharp slow turns with left/right brakes engaged to see if sound changes (this is similar to test 7 just more extreme, this would allow me to check the outboard rear axle bearings)
For all I know this sound is perfectly normal (though I doubt it). Other than the sound the tractor does not seem to be affected any other way (no obvious loss of power, etc.) Clearly the indicators point to an issue with the drivetrain and NOT the engine (since the sound stops when the tractor stops). This is where I will engage in a little speculation. If I am incorrect in my speculation on the workings of the tractor please enlighten me.
I assume that even while stopped (and not in neutral), the hydro pump is still pumping. Since the sound stops when the tractor stops this would leave me to believe that everything upstream of the hydro pump is fine (including the engine). So that leaves everything downstream of the hydro pump suspect. I guess there is a hydro impeller that takes the pumped fluid from the hydro pump and converts it to rotational motion. That could have a bad bearing. Since the sound occurs in either high/low range that would seem to indicate those bearings are fine. There must also be bearings in the diff. Perhaps test 10 will show something there. I assume that 4wd engagement occurs in the rear trans housing and not the front diff. I guess in that scenario the fore/aft driveshaft might still spin (freewheel) along with the front wheels. Could be a bearing there. Hmmm, perhaps it is time to put the tractor on blocks and start turning wheels around. Any other thoughts here?
Now for the crazy part. I've heard of people using stethescopes to diagnose sounds. This is obviously difficult for me to do since the tractor must be moving. I'm going to try to rig a microphone (a real cheap one) to various parts of the tractor. Then I'll record using a tape both under normal conditions and under conditions where the sound occurs. Perhaps this will help me narrow it down.
The tests I've tried:
1. Tried applying brakes (locked together) while driving - no weird sound occured
2. Sound occurs in high or low range
3. Stopping tractor immediatly stops the sound
4. The sound definitely happens going forward; not sure about reverse
5. PTO can be on or off and the sound occurs
6. Sound occurs in 2wd (have not tried 4wd)
7. Steering angle does not seem to affect the sound (going straight or sharp turns, sound continues)
The dealer has offered to send someone out to have a look. I appreciate this. I'm having them hold off for just a bit. I'd like to have something more concrete to tell them than, "It makes a weird sound while moving sometimes." Additional tests I want to try.
8. Does pressing the hydro pedal harder/softer affect the tone of the sound?
9. Does increasing/decreasing engine RPM affect the tone?
10. Try sharp slow turns with left/right brakes engaged to see if sound changes (this is similar to test 7 just more extreme, this would allow me to check the outboard rear axle bearings)
For all I know this sound is perfectly normal (though I doubt it). Other than the sound the tractor does not seem to be affected any other way (no obvious loss of power, etc.) Clearly the indicators point to an issue with the drivetrain and NOT the engine (since the sound stops when the tractor stops). This is where I will engage in a little speculation. If I am incorrect in my speculation on the workings of the tractor please enlighten me.
I assume that even while stopped (and not in neutral), the hydro pump is still pumping. Since the sound stops when the tractor stops this would leave me to believe that everything upstream of the hydro pump is fine (including the engine). So that leaves everything downstream of the hydro pump suspect. I guess there is a hydro impeller that takes the pumped fluid from the hydro pump and converts it to rotational motion. That could have a bad bearing. Since the sound occurs in either high/low range that would seem to indicate those bearings are fine. There must also be bearings in the diff. Perhaps test 10 will show something there. I assume that 4wd engagement occurs in the rear trans housing and not the front diff. I guess in that scenario the fore/aft driveshaft might still spin (freewheel) along with the front wheels. Could be a bearing there. Hmmm, perhaps it is time to put the tractor on blocks and start turning wheels around. Any other thoughts here?
Now for the crazy part. I've heard of people using stethescopes to diagnose sounds. This is obviously difficult for me to do since the tractor must be moving. I'm going to try to rig a microphone (a real cheap one) to various parts of the tractor. Then I'll record using a tape both under normal conditions and under conditions where the sound occurs. Perhaps this will help me narrow it down.
