B7610 sudden loss of forward / reverse power

[Ideehoan]

My mid 90s B7610 has been a 100% faithful workhorse for 20 years. I don't know it's hours as the meter reads 600.7 and that can't be right assuming the last digit is 10ths. I never pay attention to it, just do annual oil changes. Today it lost forward and reverse power. It will move on flat ground but will not climb a slight hill in forward or reverse even in low range.
Hydraulic fluid level is OK. Hydraulic power on the loader seems OK lifts front of machine easily. It had been functioning normally when I parked it a few days ago so I'm baffled.

I suspect the hydrostatic drive may have failed. Very bad timing as we are about to move and I have heavy items I would normally use the loader for.

I would appreciate any ideas for troubleshooting.

 

[jonsstihl]

the old hours meters were on a cable and 1 hr was at PTO rpm. An hour at idle would not amount to 1 hr on the meter. I think those models have a screen on the hydraulic system as well as the filters. did that get cleaned out at the last hydraulic fluid change. perhaps its a clutch issue. I'm pretty sure the hydraulic system only supplies the pre charge pressure to the system and the transmission creates its high pressure internally.

 

[Carl_NH]

Check all the linkages from the shift lever to the transmission case - there are several connections - one may have come loose. Hope it's something this simple.

 

[Ideehoan]

I just had the notion to check in 4wd as I was roading it in 2WD this morning when the trouble started. Well in 4WD I have normal drive power. Most of my work is in 4WD and I'm not sure how long since I used 2WD.
So I assume my hydrostatics are fine and the problem is with the rear diff. It's narrowed down but I'm still baffled at what can cause partial power to the rear diff. I have a foot pedal for diff lock. I assume there's a clutch in the diff?

(I did crawl under and saw nothing amiss.)

 

[Carl_NH]

Hmm this is odd - there is no clutch in the Diff and the diff lock should not change - you might try the diff lock when in 2WD and see if that makes a difference - that might give you some idea if its gear related.

For what its worth I run in 2WD most of the time and use 4WD only as needed and on gravel or grass.

 

[Ideehoan]

It just occurred to me to check 2WD function with the diff lock engaged. I have power again with the diff lock on!
So it seems the most likely failure is a broken axle shaft.
Not sure how these come apart but I'm about to find out.

 

[Ideehoan]

Looking online not finding a downloadable service manual.
Can anyone help with that? Looking for the process to change an axle.

 

[Carl_NH]

Here's a link to Messicks - on line parts diagrams - best I can do but gives you some idea of what you are dealing with, Kubota B7610HSD (Hydrostatic Transmission, 4wd) Parts Diagrams

 

[Carl_NH]

Also might try brake turning - meaning engage the RH brake, and LH brake independently to see if they both stop the wheel. This I believe is in the upper part of the case conneting to the wheel stub shaft.

Kubota B7610HSD (Hydrostatic Transmission, 4wd) Parts Diagrams

Kubota Parts Catalog Lookup. Buy Kubota Parts Online & Save!

www.messicks.com

 

[oldnslo]

Stupid question but is one of the rear tires spinning on the rim? Take a piece of chalk or paint marker and mark both tires vs valve stem. Drive around in 2 wd to see if orientation changes on one of the tires.

Sounds silly but this does happen.