bobcat 642 crazy left stick

[Yetiman]

Hey everybody. So everything was going great after I took care of my leaking Auxiliary hydraulic couplers, and was leveling out a spot in the backyard for a pool yesterday for about 2 hours. Today as soon as I pushed into the soil I basically lost all drive power on the left stick. I can still articulate the bucket without problem. In fact pushing the left stick forward almost feels like the machine wants to go backwards momentarily but with greatly reduced power. The right stick isn't suffering from any appreciable problems. I opened the "transmission" access hatch and can see that the chains for the left side of the machine are looser than the right side of the machine and should be replaced but I don't think that really address the problem. Any ideas? Am I looking at a new pump or drive motor? Any way to test? Thanks.

 

[Yetiman]

Small update. I flipped the 4 hydraulic hoses off of the pump, believing that I switched sides of the pump. I can now control the right motor with the left stick but the left motor remains dead. Guess this points to the motor, correct? Any place that I can get a rebuilt motor from with warranty? The manual for this machine has two different procedures for removing the motor, anybody able to help me decipher the age so I know what procedure? I think it's serial number is 4993m14970 Thanks

 

[Yetiman]

Small update. I flipped the 4 hydraulic hoses off of the pump, believing that I switched sides of the pump. I can now control the right motor with the left stick but the left motor remains dead. Guess this points to the motor, correct? Any place that I can get a rebuilt motor from with warranty? The manual for this machine has two different procedures for removing the motor, anybody able to help me decipher the age so I know what procedure? I think it's serial number is 4993m14970 Thanks

Well got the motor out after disconnecting the front and rear chains. Kinda a nightmare. So do I try a seal kit or find a rebuilt one?

 

[Tazza]

Well got the motor out after disconnecting the front and rear chains. Kinda a nightmare. So do I try a seal kit or find a rebuilt one?

I'd pull the motor apart and see what's damaged and replace what is broken, possibly even just needs new seals.
If you're concerned, talk to loader parts source, they can supply parts and even test it for you on their test bench.

 

[Yetiman]

I'd pull the motor apart and see what's damaged and replace what is broken, possibly even just needs new seals.
If you're concerned, talk to loader parts source, they can supply parts and even test it for you on their test bench.

Ya I plan on pulling it apart. Just trying to figure out which seal kit to get. There appears to be one for a tapered shaft with key, and one with splines. Since I had to take apart the chaincase to take the chains off the sprockets to me that would indicate that this is the tapered shaft version as the spline version would have pulled out without removing the chains from the sprockets I would think. https://photos.app.goo.gl/yWoBkQ3xVVoLb6ND8

 

[Yetiman]

Ya I plan on pulling it apart. Just trying to figure out which seal kit to get. There appears to be one for a tapered shaft with key, and one with splines. Since I had to take apart the chaincase to take the chains off the sprockets to me that would indicate that this is the tapered shaft version as the spline version would have pulled out without removing the chains from the sprockets I would think. https://photos.app.goo.gl/yWoBkQ3xVVoLb6ND8

So stupid question. How do I get the sprocket off? Lock the sprocket down and a big wrench on the nut at the end? Normal left hand thread? If that's the case I will give it a go, just don't want to wreak it any worse than it already is.

 

[Yetiman]

So stupid question. How do I get the sprocket off? Lock the sprocket down and a big wrench on the nut at the end? Normal left hand thread? If that's the case I will give it a go, just don't want to wreak it any worse than it already is.

So I disassembled the motor via the back side, and low and behold i found what the dealer service manual calls the drive shaft sheared in half. I uploaded a picture via the previous link. I still need to remove the nut at the end to get at the other half of the drive shaft... guess i will strap it down to the work bench and put a 4 foot lever on it to see if i can persuade it into yielding.

 

[Tazza]

So I disassembled the motor via the back side, and low and behold i found what the dealer service manual calls the drive shaft sheared in half. I uploaded a picture via the previous link. I still need to remove the nut at the end to get at the other half of the drive shaft... guess i will strap it down to the work bench and put a 4 foot lever on it to see if i can persuade it into yielding.

I believe you're right, the splined one looks different, that will have to be the tepered one.
Ouch, that's some damage there. But hopefully it's just the shaft and the rest is ok.
I'd suspect standard right hand thread, a big vice with say timber to help not damage the sprocket teeth. A little heat if needed, you don't have a motor attached to cause any damage to. See what the dealer and loader parts source want for a shaft, hopefully you can get it up and running again at a reasonable price.
Good luck getting the bolt off

 

[Yetiman]

I believe you're right, the splined one looks different, that will have to be the tepered one.
Ouch, that's some damage there. But hopefully it's just the shaft and the rest is ok.
I'd suspect standard right hand thread, a big vice with say timber to help not damage the sprocket teeth. A little heat if needed, you don't have a motor attached to cause any damage to. See what the dealer and loader parts source want for a shaft, hopefully you can get it up and running again at a reasonable price.
Good luck getting the bolt off

Figured I should update the community and if Nothing else the thread incase anybody comes across it in the future and needs the reference. Keep in mind my machine is a 1981 apparently. I ended up getting the large nut off the end of the drive sprocket by using a plumbers wrench with a 4 foot extension. The last gent that put the nut on used red loctite which explains why it didn't want to move. I ended up drilling and tapping the broken chunk of the dog bone shaft then threading in a 5 inch bolt. I then locked my largest pair of vice grips on the head of the bolt and passed a steel bar through the jaws of vice grips. I then grabbed and pulled (imagine grabbing a bull by the horns and yanking) till the broken chunk popped out. The reason it was stuck is that when it broke it also fractured length wise causing it to want to expand and not leave the space. With this out and the nut retaining the drive sprocket off I needed to get the drive sprocket off. I used the largest gear puller I had and it wouldn't budge. Ended up taking it to a farmer with a 30 ton press which took care of it quick. The next challenge was the shaft itself. According to Eaton / Char Lynn documentation these are 4K series drive motor. According to Bobcat they are 19 CID. That's where everything falls apart. The drive shaft I removed was 4.6 inches long requiring it be replaced with 21372-005. The drive shaft that would match a 19 CID motor Is 4.25 inches long and part number 21372-004. In the end I tried 21372-004 but once in hand it was obvious it wouldn't work. I then ordered 21372-005 from a vendor in Edmonton who got it from another vendor in Dallas Texas. This one fit like a glove. I used a seal kit from loaderpartsource, found the rubber seals perfect but found the nylon seals too large so I reused mine. So I don't know what this means. On the one hand these drive motors could come from something else (I don't know the machines full history). On the other hand if they did then what's the odds that they would also be 4K series motors? I called loaderpartsource and asked if they had the drive shaft (gave them the bobcat part number which is discontinued) and they didn't, hence why I went this route. Everything went back together as anyone would expect. Swapped the rear drive chain for the same side while I was in there since it was damaged, followed the trick of connecting the new one to the old one and rotating the tire backwards (while off the ground) to place the new chain on the rear sprocket. A chain breaker made the job easy, and zip ties to pull the two ends together worked well. One other tip I would mention is I used door shims to prop the pump up above the chain case access door under the bushings. Made it easy to get the access door out and in. Anyways, the machine is back in service after a very lengthy downtime. My last recommendation is to call a hydraulic shop for parts. These guys have communication channels between each other and can find parts fast, much faster then I can on the internet. Big thanks to PSI fluid power in Edmonton. Absolutely awesome service.

 

[Tazza]

Figured I should update the community and if Nothing else the thread incase anybody comes across it in the future and needs the reference. Keep in mind my machine is a 1981 apparently. I ended up getting the large nut off the end of the drive sprocket by using a plumbers wrench with a 4 foot extension. The last gent that put the nut on used red loctite which explains why it didn't want to move. I ended up drilling and tapping the broken chunk of the dog bone shaft then threading in a 5 inch bolt. I then locked my largest pair of vice grips on the head of the bolt and passed a steel bar through the jaws of vice grips. I then grabbed and pulled (imagine grabbing a bull by the horns and yanking) till the broken chunk popped out. The reason it was stuck is that when it broke it also fractured length wise causing it to want to expand and not leave the space. With this out and the nut retaining the drive sprocket off I needed to get the drive sprocket off. I used the largest gear puller I had and it wouldn't budge. Ended up taking it to a farmer with a 30 ton press which took care of it quick. The next challenge was the shaft itself. According to Eaton / Char Lynn documentation these are 4K series drive motor. According to Bobcat they are 19 CID. That's where everything falls apart. The drive shaft I removed was 4.6 inches long requiring it be replaced with 21372-005. The drive shaft that would match a 19 CID motor Is 4.25 inches long and part number 21372-004. In the end I tried 21372-004 but once in hand it was obvious it wouldn't work. I then ordered 21372-005 from a vendor in Edmonton who got it from another vendor in Dallas Texas. This one fit like a glove. I used a seal kit from loaderpartsource, found the rubber seals perfect but found the nylon seals too large so I reused mine. So I don't know what this means. On the one hand these drive motors could come from something else (I don't know the machines full history). On the other hand if they did then what's the odds that they would also be 4K series motors? I called loaderpartsource and asked if they had the drive shaft (gave them the bobcat part number which is discontinued) and they didn't, hence why I went this route. Everything went back together as anyone would expect. Swapped the rear drive chain for the same side while I was in there since it was damaged, followed the trick of connecting the new one to the old one and rotating the tire backwards (while off the ground) to place the new chain on the rear sprocket. A chain breaker made the job easy, and zip ties to pull the two ends together worked well. One other tip I would mention is I used door shims to prop the pump up above the chain case access door under the bushings. Made it easy to get the access door out and in. Anyways, the machine is back in service after a very lengthy downtime. My last recommendation is to call a hydraulic shop for parts. These guys have communication channels between each other and can find parts fast, much faster then I can on the internet. Big thanks to PSI fluid power in Edmonton. Absolutely awesome service.

Glad you got it sorted out, what a saga getting the dog bone out, it put up a fight, but at least you got there in the end!