T 300 stutter in track movement

[mchild]

I recently purchased a Bobcat T300 with about 4,400 hours on it. As part of the pre-purchase inspection we found and brought to the seller's attention that the left side drive control did not operate as smoothly as the right. We also noticed the left front idler was worn. Seller said the worn idler was causing it to stutter and possibly the linkage was slightly out of adjustment. The idler was replaced and the linkage adjusted. The left drive control is better than it was, but the problem has not been fully resolved.

Now that I have lived with it a little this is what I have found: there is no creep when both levers are in the neutral position and at full ground speed operation the levers seem to be in adjustment. In comparison to the operation of the right lever, the left will not start track movement as immediately as the right lever. This is forward or backward and most noticeable when trying to make small, gentle movements. When the left lever is moved, it takes more lever movement to start the track moving and often the track will not continue moving at that lever position. The track will start and then stop and sometimes after a little pause the track will move some more, other times the track will not move more without additional lever movement. This creates a stutter in the movement and often - when in work operation, the tendency is to move the lever more, which then causes much greater track movement than desired. Sometimes after that initial track movement and it has paused, the lever has to be moved up to 3/4 more before additional track movement occurs and when the track does move more it is the same start and stop or stutter. The stutter is not noticeable when the left lever is moved to nearly the full range of movement or when the loader is under way and only steering adjustments are being made by the levers. The poor operation of the left lever seems to be the same whether moving it forward or backward.

Any help is greatly appreciated.

 

[brain55]

Sounds like drive motor time to me. My experience is about 2500 hours before drive motor problems, so if those are the original motors that machine had a good run. It wouldn't surprise me if that machine had been used hard that that is it's second set of motors. The jerkiness is usually the first sign, I would check and clean the motor drain filter first. You will likely find some shavings it might even be nearly plugged. The next thing you will see is the motor pushing oil past the o-rings between the cases. I have had some luck if I catch them soon enough, in repairing them instead of replacing the motor.

 

[mchild]

Sounds like drive motor time to me. My experience is about 2500 hours before drive motor problems, so if those are the original motors that machine had a good run. It wouldn't surprise me if that machine had been used hard that that is it's second set of motors. The jerkiness is usually the first sign, I would check and clean the motor drain filter first. You will likely find some shavings it might even be nearly plugged. The next thing you will see is the motor pushing oil past the o-rings between the cases. I have had some luck if I catch them soon enough, in repairing them instead of replacing the motor.

Thanks for your reply. Not what I was wanting the hear. I don't know if the motors have been replaced but I may be able to find out.

 

[mchild]

Sounds like drive motor time to me. My experience is about 2500 hours before drive motor problems, so if those are the original motors that machine had a good run. It wouldn't surprise me if that machine had been used hard that that is it's second set of motors. The jerkiness is usually the first sign, I would check and clean the motor drain filter first. You will likely find some shavings it might even be nearly plugged. The next thing you will see is the motor pushing oil past the o-rings between the cases. I have had some luck if I catch them soon enough, in repairing them instead of replacing the motor.

I should have confirmed before replying last time. Yes, the motors have been replaced. As I was told when I purchased the machine the motors were replaced with a improved motor design as the early T300's had problems with the original motors. But, I do not know how many hours are on the current motors. Of course, I was assured the motors were fine and I would have no problems with them. Is your 2,500 hour replacement cycle experience on the new motor design?

Thank you.

 

[brain55]

I guess that depends on what they are considering improved motors and when the improvements were made. I know they changed them several years ago and that was a big enough change that you had to change sprockets too. If that was when they changed to improved motors then my 2500 hours is valid. If the change was made in the last 3 years then I have no experience with the improved motors. I had seven T300's that I was in charge of the maintenance on, we were working them hard putting close to 100 hrs a month on them.

Brian

 

[mchild]

I guess that depends on what they are considering improved motors and when the improvements were made. I know they changed them several years ago and that was a big enough change that you had to change sprockets too. If that was when they changed to improved motors then my 2500 hours is valid. If the change was made in the last 3 years then I have no experience with the improved motors. I had seven T300's that I was in charge of the maintenance on, we were working them hard putting close to 100 hrs a month on them.

Brian

Brian,

Yes, based on the way it was told to me the changed occurred several years ago. It was mentioned that the original motor was smaller than the current so it would make sense the sprocket would have to be changed. I need to see if I can find out how long ago the motors were replaced. Do you know anything about the rebuilt units from loaderpartssource.com?

Thank you.

 

[SSdoxie]

mchild, Before going to the motor try a couple simple checks first.
1. Are tracks at equal tension? You mentioned the left side idler was replaced, maybe the track is a lot tighter than the other side. Too tight of track will cause this "stutter"/hesitation feel. Raise machine up so tracks are completely off the ground, then measure distance from bottom of center most roller to inside surface of the track. Book calls for 9/16", but I have found this a little too tight when reinstalling a used track. I like to use a 9/16" socket, laying horizontal, as a feeler guage. Wall of the socket should jsut touch both track & roller wheel.
2. Check the steering linkage arm where it attaches to the pump shaft. There should be no movement of the arm on that square pump shaft. Slightest movement here can allow the piston pump to pulse when trying to slowly apply drive pressure.
If these check out OK and problem still exists, drain & change the outer bearing fluid from the motor(s). If no fluid comes out or it is thick & black like gear lube some bearing damage may have already started. This is a special synthetic fluid that Rexroth came up with for this motor, it has to flow easily to lube the duo-come seal in motor housing but able to withstand high heat of the bearing load. Bobcat & Rexroth recommend changing this oil every 500 hrs.

 

[mchild]

mchild, Before going to the motor try a couple simple checks first.
1. Are tracks at equal tension? You mentioned the left side idler was replaced, maybe the track is a lot tighter than the other side. Too tight of track will cause this "stutter"/hesitation feel. Raise machine up so tracks are completely off the ground, then measure distance from bottom of center most roller to inside surface of the track. Book calls for 9/16", but I have found this a little too tight when reinstalling a used track. I like to use a 9/16" socket, laying horizontal, as a feeler guage. Wall of the socket should jsut touch both track & roller wheel.
2. Check the steering linkage arm where it attaches to the pump shaft. There should be no movement of the arm on that square pump shaft. Slightest movement here can allow the piston pump to pulse when trying to slowly apply drive pressure.
If these check out OK and problem still exists, drain & change the outer bearing fluid from the motor(s). If no fluid comes out or it is thick & black like gear lube some bearing damage may have already started. This is a special synthetic fluid that Rexroth came up with for this motor, it has to flow easily to lube the duo-come seal in motor housing but able to withstand high heat of the bearing load. Bobcat & Rexroth recommend changing this oil every 500 hrs.

Dennis,

When the idler was replaced the mechanic that did it stated the same as you about keeping the tracks just a little looser and he did check the track at the same time as the machine was up in the air. I will recheck to make certain. I have been reading up on the shaft & pintle issue and plan to check that also. Do you have an easy way to check the shaft while operating the levers to make sure there is not slop there? Also, how do you check/change the outer bearing fluid on the motor? Many thanks for your suggestions.

 

[SSdoxie]

If the pintle arm starts to wear it is usually visible by just watching the arm to shaft for any free play.
There is a flush hex plug in the end of the axle hub wear sprocket bolts on. Put the plug at bottom (6 O'clock) and drain oil to drain the oil, rotate the hub so plug is about 3 or 9 O'clock and add new oil. The oil sold through Bobcat comes in bottle with enough oil for both motors, just put 1/2 bottle in each motor.
Before draining the oil, run/spin the motor a few minutes to warm the oil so flow easier. If you see any signs of metal or no oil comes out then bearing is starting to fail. You can replace just the outer housing of the motor, do not need to purchase complete new motor if not needed.

 

[mchild]

If the pintle arm starts to wear it is usually visible by just watching the arm to shaft for any free play.
There is a flush hex plug in the end of the axle hub wear sprocket bolts on. Put the plug at bottom (6 O'clock) and drain oil to drain the oil, rotate the hub so plug is about 3 or 9 O'clock and add new oil. The oil sold through Bobcat comes in bottle with enough oil for both motors, just put 1/2 bottle in each motor.
Before draining the oil, run/spin the motor a few minutes to warm the oil so flow easier. If you see any signs of metal or no oil comes out then bearing is starting to fail. You can replace just the outer housing of the motor, do not need to purchase complete new motor if not needed.

Dennis,

Thanks for this info. If the hub has oil but it is dark then it should be drained and replaced. If the drained oil has metal debris then probably will need at least outer housing. Correct? I don't see the outer housing as a separately available part on the Bobcat parts listing. Is it available from other sources? Thanks again.