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Case 646 Drive Issues


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#1 twostep OFFLINE  

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Posted August 07, 2013 - 03:11 PM

I've got a neighbor that has a 646 with loader and backhoe (that I've been trying to buy ever since I moved here). Onan engine. The back hoe works fine, with fine power, the front loader hydralics work fine as well but he says that when driving he has to keep it in low range and still bogs down and has almost no drive power. Does anyone have any idea what would cause this? I will say that the return line from the backhoe valves looks like it is kinked slightly but I'm not sure that it is enough to cause issues.

 

Thanks for any help.


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#2 gopher OFFLINE  

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Posted August 07, 2013 - 07:47 PM

I don't know anything of loaders but same o same o .Doesn't sound like pump issue. Using right oil,oil level right? Does it bog in reverse ? First thing to check would be TCV might be broken relieve valve spring. If it does same in reverse it does not completely rule out the TCV but points stronger to drive motor issues. Check pressure on TCV. You could check drive motor end cap bolts if lose can effect drive motor.On other hand if reverse is not effected it's something in TCV.


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#3 dropped82 OFFLINE  

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Posted August 07, 2013 - 10:12 PM

I think gopher is on it. The drive motor or rearend would be my first culprit. Check to see if the brake is dragging. If the brake is good then pull the drive motor. Do you have one to swap it with to see if it still does it. Could be the TCV but with it being open center I don't see it bogging the engine down. The fluid will go the path of less resistance. So if the TCV is causing the problem it would just bypass it and not move. Which I couldn't see it dragging the motor. Is the pressure relief whistling when its under load moving?


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#4 twostep OFFLINE  

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Posted August 07, 2013 - 10:28 PM

Thanks for the ideas guys. I'll take these to him and see if we can narrow it down. I'm researching this to help him out and I don't know all of the symptoms exactly... but I will get more info.



#5 gopher OFFLINE  

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Posted August 07, 2013 - 11:46 PM

My mistake I thought you meant it was loosing drive power not motor power. If it's bogging motor there is  oil restriction somewhere in drive  circuit or binding in gearing. One thing with BH he can run stabilizers down and turn the wheels and to tell if something wrong in gear housing.  


Edited by gopher, August 08, 2013 - 12:01 AM.


#6 twostep OFFLINE  

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Posted August 08, 2013 - 09:08 AM

Yes, it bogs the engine down when trying to drive. I will have him lift the rear end up and see how well it spins the tires first off.



#7 gopher OFFLINE  

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Posted August 08, 2013 - 05:31 PM

How much of a kink in line? Cause if like others the oil would go through loader valves before the TCV so it is possible kink might be the cause of it . Seeing how it would be on the pump side of any  relief valves.Putting back  pressure on pump.I don't know how much of a kink it'd have to be to give the symptoms he has.  


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#8 twostep OFFLINE  

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Posted August 08, 2013 - 10:07 PM

How much of a kink in line? Cause if like others the oil would go through loader valves before the TCV so it is possible kink might be the cause of it . Seeing how it would be on the pump side of any  relief valves.Putting back  pressure on pump.I don't know how much of a kink it'd have to be to give the symptoms he has.  

It's not that bad of a kink but it probably cuts the lines diameter in half... He is out of town this weekend... and I've got my own junk to work on this weekend too! but next week I'll get with him and do some more investigation.


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#9 dropped82 OFFLINE  

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Posted August 09, 2013 - 06:14 PM

The kink in the return line will make the hydro system see a load. Which in turn will make the engine work harder. If that kink is in series with the TCV then the pump will see it as a load (like a valve open). That's how the Case systems work. No pressure in the system till a valve is opened creating a "kink" in the sytem. Which results in pressure. Pressure means load on the engine. I think Gopher is on it with the kink causing the problem.

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#10 coop OFFLINE  

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Posted August 10, 2013 - 10:10 AM

There is a bannana plate that controls direction and flow to the drive motor, if that is out of adustment or worn(missing) bushings it could cause the condition you are describing.



#11 twostep OFFLINE  

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Posted February 06, 2014 - 09:45 AM

A little update one this: He decided to rebuild the Onan when he discovered that he only had 30 and 40psi compression after rebuild we got 95 and 100 (if memory serves me). Rebuilt the carb and we got it tuned in pretty well. He also rebuilt the front spindles (had a machine shop make some oilite bushings... 4 of them for $25). While working on it he went ahead and replaced the 30 some odd year old tires front and rear.While we had the rearend up on stands I found the rear end spun freely... we can cross brake drag off the list.

 

He said that the bannana plate had some slop but I'm not sure if he plans to reply it or not. He also picked up a replacement drive motor for the rear end just in case. He should have it back together very soon so I'll post up the results.


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#12 gopher OFFLINE  

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Posted February 06, 2014 - 07:30 PM

Sounds like a case of tired motor. I think bad banana plate give jerky and not full range of travel control.



#13 Mjoe7 OFFLINE  

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Posted February 07, 2014 - 07:00 AM

The replacement hydraulic drive motor is the same part number used on the 400 series high wheel tractors.



#14 Case-Closed OFFLINE  

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Posted April 05, 2014 - 09:59 PM

Before I replaced my banana plate I had similar issues.  Get the plate, bushings, updated holding unit and a couple of the ball screw units that go between the valve body and linkage. A tiny bit of play is all it takes to get sluggish performance. I also had a worn out pump and my engine was shot so I replaced it with a Kohler CH-18 and an Eaton pump.

 

IMG_0886.JPG IMG_0889.JPG


Edited by Case-Closed, April 05, 2014 - 10:03 PM.





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