743 Drive Motor Seal Replacement Process

[Garauld]

I was losing hydraulic fluid to the chain case - a sign the seals in the drive motors are shot so I replaced them. Here's a chronicle of the process I followed. I had to buy the drive motor seal kits, quad and shaft seals to complete the job - about 6 hrs to do both sides. It wasn't that difficult.

1. Pull the front level plug and drain the chain case so no more oil comes out.
2. Place a log under the bucket and get the front wheels a several inches off the ground.
3. Remove one of the front wheels.
4. Remove the cover hiding the subject drive motor.
5. Clean the chassis and motor as well as feasible.
6. If you plan to disassemble the motor, crack loose (slightly) the four motor housing bolts - it's easier while the motor is on the machine as they are very tight.
7. Place an oil pan under the motor and disconnect the three hoses. Expect about a cup of oil to leak out of the hoses.
8. Plug the ports on the motor - I used plastic caplugs.
8. Remove the four motor mounting bolts and pull out the motor off the loader chassis.
9. Rotate motor over a pail to drain residual oil.
10. Clean the motor housing real well - I use Coleman white gas.

If you plan to dissassemble the motor, jump to #21.

11. Use a sharp tool (Xacto) and pick out & replace O-ring in base mounting flange bore.
12. Use a medium screwdriver and push back the outer rim of the large ring seal (located in the reduction gear box) just enough to get the teeth of a 6" pair of vise-grips on it. I made a threaded adapter for my slide hammer so I could attach it to the vise grips. You may need to remove a bit of rubber seal material so the vise-grips get a good bite. A few hammer whacks and the seal popped right out.
13. Using a magnetic pickup, pull out the large flat steel washer that was behind the shaft seal.
14. Remove and replace the quad seal behind the washer. Reinstall the washer.
15. Using a flat brass drift, install a new shaft seal.
16. Remove and install a new O-ring on the motor housing mating face. I use grease to hold it in place.
17. Reinstall the motor.
18. Reattach the hoses.
19. Start up the Bobcat, drive around a bit and look for leaks.
20. Reattach the motor cover.

21. While over a pail, remove the plugs in the motor hose fittings and attempt to drain out as much oil as possible.
22. Clean the motor again.
23. Using a marker, draw a witness line down the side of the motor.
24. Unscrew the four housing bolts keeping the motor mostly together. Try and keep the shaft centerline horizontal or you risk letting the geroler pieces fall out.
25. Disassemble the motor's sections slowly so nothing falls on the floor.
26. Replace seals and O-rings as needed. The kit has all of them. A bit of grease helps hold the O-rings in place.
27. To time the motor, refer to the motor timing instructions: http://hydraulics.eaton.com/products/pdfs/07-118.pdf
28. As explained in the instructions, look thru the open ports and then either turn the valve CCW 1/2 a tooth or turn the housing and toothed shaft CW 1/2 a tooth to mate them.
27. On reassembly, add a drop of oil onto the housing bolts and reassemble motor. Retorque bolts after reinstalled on loader.
28. If the motor turns the wrong way, revert back to timing instructions.

 

[Tazza]

Excellent guide. This is pretty much exactly what i do too. The only difference was the main seal, i drilled a hole and screwed in a self tapping screw and levered it out.
The only thing i would add is to loctite the threads of the 4 bolts with servicable sealant. This prevents oil slowly wicking up the threads and leaking out around the 4 bolt heads of the drive motor.

 

[dabaines]

Excellent guide. This is pretty much exactly what i do too. The only difference was the main seal, i drilled a hole and screwed in a self tapping screw and levered it out.
The only thing i would add is to loctite the threads of the 4 bolts with servicable sealant. This prevents oil slowly wicking up the threads and leaking out around the 4 bolt heads of the drive motor.

Sorry to revive this old thread, but it's relevant to my issue today. The geroler pieces fell out of the drive motor how the heck do I get them back in? Can't find anything on youtube.

 

[dabaines]

Sorry to revive this old thread, but it's relevant to my issue today. The geroler pieces fell out of the drive motor how the heck do I get them back in? Can't find anything on youtube.

Carefully I put it back in place with a press. Is it supposed to be that tight? Need to pick up some hose before I can test it out. I am guessing that I will have all kinds of issues on start up.

 

[Tazza]

Carefully I put it back in place with a press. Is it supposed to be that tight? Need to pick up some hose before I can test it out. I am guessing that I will have all kinds of issues on start up.

You shouldn't have needed a press to get them back in, just oil them up and push them in. They are meant to be tight, it means it's not worn.
You should be able to get hold of the output shaft with a pair of channel lock pliers and get it to rotate, it will be tight, but should turn. If it's bound up solid, something is wrong.
It it moves, you should be good to go.

 

[dabaines]

You shouldn't have needed a press to get them back in, just oil them up and push them in. They are meant to be tight, it means it's not worn.
You should be able to get hold of the output shaft with a pair of channel lock pliers and get it to rotate, it will be tight, but should turn. If it's bound up solid, something is wrong.
It it moves, you should be good to go.

Thanks for the reply, Tazza. I took it apart again and put it back together. I have lost all steering on that side of the cat. Feeling dejected tonight.

 

[dabaines]

Thanks for the reply, Tazza. I took it apart again and put it back together. I have lost all steering on that side of the cat. Feeling dejected tonight.

The shuttle valve is the original issue. The rubber was causing a leak. If this isn't installed properly (plug installed instead of bushing), would this cause the loss of control and it still leaking? If so, how do I setup the valve properly? I am a complete newbie.....this forum is saving my ass!

 

[dabaines]

The shuttle valve is the original issue. The rubber was causing a leak. If this isn't installed properly (plug installed instead of bushing), would this cause the loss of control and it still leaking? If so, how do I setup the valve properly? I am a complete newbie.....this forum is saving my ass!

Just wanted to add these pdf's as reference for others having issues: Drive motor: http://jkfabrication.com/content/6000%20Charlynn.pdf Parts and cut-out sheets for practically every make or model bobcat: https://www.bobcatpartsonline.com/#/catalogBrowser (just need serial #) Little background: The previous owner had tried to JB weld over the screw for the shuttle valve. I thought it was a crack in the motor housing. I removed the motor by extracting the four bolts that hold the sections together (dumb mistake). The geroler fell out and I put it back together without much research. I grinded off the JB weld to discover what I assumed was a drain valve that was leaking due to a bad rubber. I had to replace the screw in plug but couldn't find a part that didn't counter sink. So I used a plug off the shelve that likely does not let the shuttle seat properly. Once back together I installed and how no control over this side of the bobcat and was left scratching my head. FYI - This whole mess I am in could have been avoided if I did my homework prior to digging in on fixing this leak. I just hope I can get it back to running again. Update on the issue: I didn't setup the timing correct and the shuttle valve was not seated properly. I think it safe to assume that is the cause of me completely losing control of a perfectly running machine prior to disassembly.

 

[dabaines]

Just wanted to add these pdf's as reference for others having issues: Drive motor: http://jkfabrication.com/content/6000%20Charlynn.pdf Parts and cut-out sheets for practically every make or model bobcat: https://www.bobcatpartsonline.com/#/catalogBrowser (just need serial #) Little background: The previous owner had tried to JB weld over the screw for the shuttle valve. I thought it was a crack in the motor housing. I removed the motor by extracting the four bolts that hold the sections together (dumb mistake). The geroler fell out and I put it back together without much research. I grinded off the JB weld to discover what I assumed was a drain valve that was leaking due to a bad rubber. I had to replace the screw in plug but couldn't find a part that didn't counter sink. So I used a plug off the shelve that likely does not let the shuttle seat properly. Once back together I installed and how no control over this side of the bobcat and was left scratching my head. FYI - This whole mess I am in could have been avoided if I did my homework prior to digging in on fixing this leak. I just hope I can get it back to running again. Update on the issue: I didn't setup the timing correct and the shuttle valve was not seated properly. I think it safe to assume that is the cause of me completely losing control of a perfectly running machine prior to disassembly.

Finally, this job is complete. It's actually running better than it did before. Plus - No leaks anymore. I am not leaving a trail of fluid behind me. Tazza, Thank you.