Hey guys, I have a 773 that is having a drive problem on the right side. It will not go forward or reverse and makes a "grinding" noise when pushing the lever forward or reverse. Im stumped. I pulled the chaincase covers and everthing appears good. I was told it was probly the seals in the motor so i bought the $109 seal kit from my Bobcat dealer and replaced seals in the motor. But when I reinstalled it, it did the exact same thing. I dont know what to try next... I mean to me, its seams and sounds like the spline shaft from the motor to the final drive is slipping inside the hub but the spline shaft looked pretty goon on the motor seal kit rebuild.. has anyone ever experienced this? What likely it could it be?
Help Support SkidSteer Forum:
walio123
Well-known member
- Joined
- Dec 9, 2013
- Messages
- 348
Check if you can turn the wheels by hand when the machine is lifted.f you can, then something is wrong with the splines of the hydromotor shaft /it has 2 end with splines,one that goes to motor carier one inside motor. There are also hydromotors with anoter shaft inside also with splines.I/ Also check slpines in motor carier. If you can not rotate tyres by hand , there must be parking brake issue. Do you remove center cover on chain case?
After i removed the right side drive for rebuild, I jacked the machine up and was able to move the wheels freely. I did this to make sure something wasnt binding in the chain drive portion. I have not lifted and tried to turn the wheels with the motor installed yet but i will this weekend. As far as the parking break.. mine does not have one on it, i gues it was removed by a previous owner. I also pulled the solenoid off that attaches to the cover over the motor drive sprockets and it appeared to me like someone had gutted it as there was nothing there attached to the bottom of it that would engage the parking brake plates.
So I put a seal kit into the right side drive motor and it still does the same exact thing, machine just shutters with any load on the right side drive. I swapped the right and left drive motors and the problem stays with the right side. I think now theres not much left besides the hydrostatic pump or the solenoid valve on the right side where the case drain line connects too. Does anyone have any info on the 2 solenoid valves that i am refering too where the right side drive case drain line connects too? Im not sure how or when they operate.
walio123
Well-known member
- Joined
- Dec 9, 2013
- Messages
- 348
The case drain line must be connected directly to the tank, through the filter, in some machines there is one filter in some two. The block can be used as a tee to join the lines of the two hydromotor and return to the tank through a filter. It should be free, because if it is clogged it will damage the shaft seal and cause the hydraulic oil to leak into chain case. Solenoids have nothing to do with the work of the hydrostatic system. Did not write whether you can roll the right wheels by hand when the machine is lifted and the hydromotor is s in place? If you can, and this sound is heard, then you have damaged splines on motor carrier shaft and sprocket. Try to find out where the sound comes from. You can use a wooden stick like a stethoscope. A fault in the hydrostatic pump doubts me, because the right wheels take a movement from the section to which the gear pump is attached, and if the splines between two pupms are damaged there, the hydraulic system will also not work.There may be a damaged rotor group on the pump, but I doubt there is only one section.
I forgot to mention that I did try and turn the wheels with it lifted, powered up and motors installed. I could turn it by hand even though it felt like something was going on inside it when i did. Looking at parts breakdowns for my machine, the final drive shaft is one piece with a female spline on one end and double sprocket on the other. When i pulled the center gearcase cover off i could see the sprocket and it looked ok, so I doubt the shaft is slipping or broken. I still think the right side of that hydrostatic pump has an issue with the piston or plate. I eill be taking it to a heavy repair shop friday to evaluate and potentially rebuild the hydrostatic pump.
Personally, i'd swap motors from side to side to see if the motor is damaged and the dealer missed it. The motor should not turn by hand when full of oil, bad pump or not.
I did swap the motors and the problem stayed with the right side. Theres not much left in the system besides the pump if its not the motor or the final drive portion right?
If that piston inside the pump for that sides drive is damaged it would allow you to turn the wheels by hand correct?
Wear in the pistons or the wear plate, it could allow it to rotate.
It does sould like it's the pump, you have done the checks, either the pump or the relive valves in the pump. When you have it out and open, hopefully it will be easy to identify what is damaged.
