Question for Tazza

[cumminsguy]

My drive motors are leaking into my chain case, 743b model the i.d plates tell me its the 6657024 motors, this is the machine that I have had foward and revers issues that come and go, well the chain case had about 10 extra gals of oil in it, my guess is the last owner just kept adding oil. All this being said can you give me any advise on re-sealing the drive motors I will get the kits from PLS. Thanks again. Tom

 

[Tazza]

If it's only leaking into the chain case, the only seal you need to replace is the drive motor carrier. The motor has no seals as such to prevent oil getting into the chain case, that part is open to the case drain line.
First thing to check/replace is the case drain filters, not sure if they were fitted to the 743B or not, or of it was the next model that they started. Trace back the small lines from the drive motors back to the pump and oil tank looking for alloy cylinders, these have filters inside that if they block up, oil will get into the chaincase due to pressure build up.
Now, the seal. You need to remove the drive motors, look at the shaft the motor shaft goes into, there will be a big black seal that seals around it. This is what you need to remove and replace. You can drill a small hole in it and screw in a self tapping screw in and use pliers to pull it out. Replace it and the motors, you shoudl be good to go. I believe the dealer has these at a reasonable price as well.

 

[cumminsguy]

If it's only leaking into the chain case, the only seal you need to replace is the drive motor carrier. The motor has no seals as such to prevent oil getting into the chain case, that part is open to the case drain line.
First thing to check/replace is the case drain filters, not sure if they were fitted to the 743B or not, or of it was the next model that they started. Trace back the small lines from the drive motors back to the pump and oil tank looking for alloy cylinders, these have filters inside that if they block up, oil will get into the chaincase due to pressure build up.
Now, the seal. You need to remove the drive motors, look at the shaft the motor shaft goes into, there will be a big black seal that seals around it. This is what you need to remove and replace. You can drill a small hole in it and screw in a self tapping screw in and use pliers to pull it out. Replace it and the motors, you shoudl be good to go. I believe the dealer has these at a reasonable price as well.

Thank you for the reply, I had thought that the o-rings seals etc. in the drive motor could be why the foward and revers drive would fade do you think that its more than bad seals causing my drive issue, you said replace the motor, should I try the seal kit first along with the carrier seal? thanks, Tom

 

[Tazza]

Thank you for the reply, I had thought that the o-rings seals etc. in the drive motor could be why the foward and revers drive would fade do you think that its more than bad seals causing my drive issue, you said replace the motor, should I try the seal kit first along with the carrier seal? thanks, Tom

It is possible. Depending on the type of drive motor, if it's the one i'm thinking of, there are 2 seals that when they degrade you loose drive power. They cost me abour $5 for two motors from a seal shop. They were simply O rings, no need for a seal kit.
It is your call if you pull it down, it wouldn't hurt. You will need to reaplace the carrier seal still.

 

[cumminsguy]

It is possible. Depending on the type of drive motor, if it's the one i'm thinking of, there are 2 seals that when they degrade you loose drive power. They cost me abour $5 for two motors from a seal shop. They were simply O rings, no need for a seal kit.
It is your call if you pull it down, it wouldn't hurt. You will need to reaplace the carrier seal still.

Thanks, may give it a shot, hey I also did find the filter in the alloy housing on the parts look up, seems just 1 filter in there with a tee going to it from both drive motors, will post back after I pull it and check it out, Thanks again for all your help Tom

 

[Tazza]

Thanks, may give it a shot, hey I also did find the filter in the alloy housing on the parts look up, seems just 1 filter in there with a tee going to it from both drive motors, will post back after I pull it and check it out, Thanks again for all your help Tom

They must have just used one on them, they started using two on the newer machines. It just filters the case drain oil. This way, if a motor was to destroy its self, there is more of a chance the pump will not be damaged.
When these filters plug up, the line gets more back pressure that may exceed the seals rating and push past it and into the chain case. Old age can also make the seals fail.

 

[cumminsguy]

They must have just used one on them, they started using two on the newer machines. It just filters the case drain oil. This way, if a motor was to destroy its self, there is more of a chance the pump will not be damaged.
When these filters plug up, the line gets more back pressure that may exceed the seals rating and push past it and into the chain case. Old age can also make the seals fail.

Well the Drive motor seal kit fixed the issue, Nice strong forward drive now, the one o-ring beneath the white plastic shield (larger diameter) was totally shot in a thousand pieces and the other smaller white plastic shield around the center of the motor didn’t even have the o-ring, it was non existing, I will do the same on the other drive motor to freshen that one up too, but man its smooth as silk when turning now and pleanty of power. I will upload a few of the pics I took so others with the same problem can see the failed seals. Many thanks. Tom

 

[Tazza]

Well the Drive motor seal kit fixed the issue, Nice strong forward drive now, the one o-ring beneath the white plastic shield (larger diameter) was totally shot in a thousand pieces and the other smaller white plastic shield around the center of the motor didn’t even have the o-ring, it was non existing, I will do the same on the other drive motor to freshen that one up too, but man its smooth as silk when turning now and pleanty of power. I will upload a few of the pics I took so others with the same problem can see the failed seals. Many thanks. Tom

Sounds like the 753 i got a few years back. The O ring under the plastic seal was like bread crumbs. Replaced the O rings there and the others between segments and it was as strong as ever. I took the parts to my local seal shop and they matched them. As long at the plastic seals aren't cracked, you only need the O rings. If they are cracked, you need a kit.
Glad the seal kit fixed it and you managed to time the motor when you put it back together. It can be tricky to get it spot on. If it's out, it will run backwards.
Just remember this will not fix the leaking into the chain case issue. That is a different seal.

 

[cumminsguy]

Sounds like the 753 i got a few years back. The O ring under the plastic seal was like bread crumbs. Replaced the O rings there and the others between segments and it was as strong as ever. I took the parts to my local seal shop and they matched them. As long at the plastic seals aren't cracked, you only need the O rings. If they are cracked, you need a kit.
Glad the seal kit fixed it and you managed to time the motor when you put it back together. It can be tricky to get it spot on. If it's out, it will run backwards.
Just remember this will not fix the leaking into the chain case issue. That is a different seal.

Timing the motors was easy, I took pics of how it came apart (Camera phones are great) and just picked up the 2 case oil seals # 6705847 so now that the job I had to finish is completed I can pull the drive motors back off and install the new seals, How do you post pics on this site?, I would like to show the damaged parts. Tom

 

[Tazza]

Timing the motors was easy, I took pics of how it came apart (Camera phones are great) and just picked up the 2 case oil seals # 6705847 so now that the job I had to finish is completed I can pull the drive motors back off and install the new seals, How do you post pics on this site?, I would like to show the damaged parts. Tom

You did well. You need to be careful how the valve plate lines up with some holes, seems like you were lucky enough to get it back in the right places.
As for pictures, upload them to a file host like photobucket. When there, open the image up, right click/copy then right click paste it to the forum. It should show up.

 

[SkidRoe]

Timing the motors was easy, I took pics of how it came apart (Camera phones are great) and just picked up the 2 case oil seals # 6705847 so now that the job I had to finish is completed I can pull the drive motors back off and install the new seals, How do you post pics on this site?, I would like to show the damaged parts. Tom

I know this is "Question for Tazza", but here is a tutorial on posting pictures: http://www.skidsteerforum.com/DesktopDefault.aspx?tabid=54&frmView=ShowPost&PostID=2445

 

[cumminsguy]

I know this is "Question for Tazza", but here is a tutorial on posting pictures: http://www.skidsteerforum.com/DesktopDefault.aspx?tabid=54&frmView=ShowPost&PostID=2445

Hey Tazza, quick question for ya, I just ordered new pistons and poppets for my right drive motor due to the heaviy scoring wear on the old ones, the parts list from bobcat only shows 1 piston being required #6513510, the drive motor on my machine has 2 install beneath the allen head plugs, is this correct or should it only have 1 installed? Thanks for any help you can give. Tom

 

[Tazza]

Hey Tazza, quick question for ya, I just ordered new pistons and poppets for my right drive motor due to the heaviy scoring wear on the old ones, the parts list from bobcat only shows 1 piston being required #6513510, the drive motor on my machine has 2 install beneath the allen head plugs, is this correct or should it only have 1 installed? Thanks for any help you can give. Tom

Are you talking about a allen headed plug near the case drain hose that you can see from the opposite end of the motor shaft? It has a spring, poppet and a metal rod? If so, that is your shuttle valve. There are two springs, one each side and two poppets, one each side as well.
I'm not aware of any pistons in these motors, later model larger machines had piston motors.

 

[cumminsguy]

Are you talking about a allen headed plug near the case drain hose that you can see from the opposite end of the motor shaft? It has a spring, poppet and a metal rod? If so, that is your shuttle valve. There are two springs, one each side and two poppets, one each side as well.
I'm not aware of any pistons in these motors, later model larger machines had piston motors.

Yep your right, when I resealed the motors I had not pulled the plugs out to get to the shuttle valve and thought that each plug had a valve behind it not knowing it was just 1 valve between the 2 plugs. I installed a new shuttle valve yesterday hoping that it was the cause to a weak acting reverse on the left side of the machine, foward, both sides work perfect and smooth even the right reverse is perfect so I quess its time to look into the pressure relive valve on the pump. Thanks for the reply. Tom

 

[Tazza]

Yep your right, when I resealed the motors I had not pulled the plugs out to get to the shuttle valve and thought that each plug had a valve behind it not knowing it was just 1 valve between the 2 plugs. I installed a new shuttle valve yesterday hoping that it was the cause to a weak acting reverse on the left side of the machine, foward, both sides work perfect and smooth even the right reverse is perfect so I quess its time to look into the pressure relive valve on the pump. Thanks for the reply. Tom

It is starting to look more and more like the relief. Did you try swapping motors to be 100% sure?

 

[cumminsguy]

It is starting to look more and more like the relief. Did you try swapping motors to be 100% sure?

No, dont think its the motor, I pulled the relief valve behind the linkage and switched it with the other side, the 1 thats easy to get to so after I put the linkage back on I'll test it out. At least if its a bad valve it will be on the right side and easy to change at this point. I did cap off the 2 drive motor lines and do the stall test, it stalls easy foward but takes alot to stall it in reverse so we will see tonight if its the relief valve.

 

[Tazza]

No, dont think its the motor, I pulled the relief valve behind the linkage and switched it with the other side, the 1 thats easy to get to so after I put the linkage back on I'll test it out. At least if its a bad valve it will be on the right side and easy to change at this point. I did cap off the 2 drive motor lines and do the stall test, it stalls easy foward but takes alot to stall it in reverse so we will see tonight if its the relief valve.

With that stall test, i think you are right.
What's the bet the relief you need is on the bottom? There are two on the top, two on the bottom. One for each side and one for each direction.

 

[cumminsguy]

With that stall test, i think you are right.
What's the bet the relief you need is on the bottom? There are two on the top, two on the bottom. One for each side and one for each direction.

Well its not the high pressure relief valve, nothing changed so I'll try the replenishing valve next, maybe the spring is broken.

 

[cumminsguy]

Well its not the high pressure relief valve, nothing changed so I'll try the replenishing valve next, maybe the spring is broken.

Ok so switched the valves (replenishing) and still no improvement so like you said I now have switched the drive motors and the problem followed the drive motor, I took it back apart and all looked good, blew air and cleaned the entire assembly and re-assembled with the new seal kit again, tested and still weak driving foward then hits hard and turns. When the motor was on the other side revers was the same way ( to be expected right? ) so the question is there is a small brass disc on 1 of the inside surfaces that I think controls pressure, it seems to fit loose could this cause the pressure drop I am having? the drive motor has a ton of power in 1 direction so I want to belive the geo assembly is good, any thoughts?