742b drive problem

[dfb]

I recently developed a problem with the left side drive of my 742b. The right side operates normally, a small amount of stick movement gets a small amount of movement from the machine. On the left side, you keep moving the stick forward with no machine movement and suddenly it "kicks in". The left side is driving slower also, over distance the machine is now going to the left and requires correction with the right stick. What testing would be in order to determine where the problem is? Is swapping the drive motors side to side possible to see if the problem follows the motor if that is a possible cause? Thanks!!

 

[Tazza]

Swapping drive motors is a good place to start. The only issue is the fittings, they are different directions and angles from side to side, so you will need to change those when you move the motors.
If the issue is the motor, you can re-seal them and hopefully fix it.

 

[dfb]

Swapping drive motors is a good place to start. The only issue is the fittings, they are different directions and angles from side to side, so you will need to change those when you move the motors.
If the issue is the motor, you can re-seal them and hopefully fix it.

I may not be able to swap motors til the weather improves here but thought it worth mentioning that there is no problem in reverse. Both motors turn the same speed and the control of the left side is normal in all stick positions with none of the jerking that it does in forward. Can a pump behave differently between forward and reverse?

 

[flyerdan]

I may not be able to swap motors til the weather improves here but thought it worth mentioning that there is no problem in reverse. Both motors turn the same speed and the control of the left side is normal in all stick positions with none of the jerking that it does in forward. Can a pump behave differently between forward and reverse?

It sounds like it might be a linkage problem, some models have an aluminum bar that connects to a square shaft on the Vickers pump that can get wallowed out and have some slop.
The fact that it performs fine in reverse contra-indicates a pump or motor issue.

 

[Tazza]

It sounds like it might be a linkage problem, some models have an aluminum bar that connects to a square shaft on the Vickers pump that can get wallowed out and have some slop.
The fact that it performs fine in reverse contra-indicates a pump or motor issue.

Linkages are a possibility.
There is a remote possibility that there is an issue with the relief valve in the pump for forward.
The other things it could be are all in the motor its self, shuttle valve stuck or a bad seal.
A bad seal in the motor makes sense as the high pressure fluid can flow from in to out without doing work inside the motor. If one seal is bad, it will mean one direction will be fine, but the other direction is the issue.

 

[dfb]

Linkages are a possibility.
There is a remote possibility that there is an issue with the relief valve in the pump for forward.
The other things it could be are all in the motor its self, shuttle valve stuck or a bad seal.
A bad seal in the motor makes sense as the high pressure fluid can flow from in to out without doing work inside the motor. If one seal is bad, it will mean one direction will be fine, but the other direction is the issue.

I swapped the motors yesterday and the problem followed the motor. It now exhibits the problem in reverse on the side where the motor in question went. What are my options for fixing this? Does anybody rebuild these?

 

[Tazza]

I swapped the motors yesterday and the problem followed the motor. It now exhibits the problem in reverse on the side where the motor in question went. What are my options for fixing this? Does anybody rebuild these?

Crack it open and inspect the seals, see if any look bad. You can get a seal kit to repair them.
When putting back together, you need to time it.
If you look up my profile, send me an email and i can send you the manual for the motor repair.