B7500 faster in reverse than forward

[TNGP]

Good morning everyone! I've been referring to this website for a long time, but I've got a question that I can't find an answer to so I signed up.

My 2004 Kubota B7500 (no FEL) travels faster in reverse than forward on level ground. I've checked the linkages and the limiting screws are not the cause. The reverse screw stops the pedal, the forwards crew is 1/16 inch from touching the pedal at full throttle.

The only time the tractor speeds up is when I drive up an incline. In a noticeable bump and the tractor takes off. Once on level land again, it slows down to a more moderate speed. This has got me puzzled. This only happens in high range.

The fluids are all new with factory filters. The HST is running on syntractor III by royal purple. All other fluids are appropriate royal purple products.


This one has me puzzled. Possibly a weak or stuck fluid bypass spring or valve? Maybe a gremlin diverting fluids? Let me know what you think to try and get this figured out.

 

[GManBart]

Almost all tractors are faster in reverse than in forward. For example, my case backhoe lists a 25.5mph max in forward, and 30.8mph in reverse.

With an HST tractor you sometimes have to ease off the pedal a bit to let the machine accelerate when in high range, and then you can gradually go to full forward pedal. This is more common with machines that only have two ranges....high is simply too high in many situations. Still, it's likely to be faster in reverse than forward no matter what you do.

 

[TNGP]

Ok. I will try that later today. Does that explain the sudden jump in speed when traveling uphill only?

 

[GManBart]

Ok. I will try that later today. Does that explain the sudden jump in speed when traveling uphill only?

It could. When you hit a hill it adds a load and diesels respond to a load with more fuel (your throttle setting only sets the RPM, not how much power the engine makes). Depending on exactly how your HST is set up it might not be capable of putting enough load on the engine in high range to make the engine put out more power.

 

[TNGP]

Gman,

That absolutely makes sense. I was debating a fuel flow meter, I might have to do that to keep tabs on everything. How exactly do I change the settings to keep enough load to keep it a steady speed?

I tried this afternoon to go 70% throttle, then slowly to 100%. The only thing that happened on level ground was my speed increased. It still wasn't full speed until I got over to the steep part of the second drive way then it again took off. I could hear the engine take on some load at the same time with a little puff of smoke from the exhaust.

This seems to support your thought, I'm just perplexed that such a small amount of drag (going up hill) could step up the fuel delivery.

Thank you for your input. You've done schooled me. I'm open to anything else you've got!