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4640 vibration?

tomstractorsandtoys

tomstractorsandtoys

Well-known Member
My nephew has a 4640 quad that has a bad vibration. The tractor is 800 miles away and I have not seen it. It has broken two of the cast brackets that hold the hyd. pump in the past year. The trans was gone thru so they do not feel the problem is there. One shop suggested that the crankshaft is broke? The tractor runs and operates and does not knock. Where should they start? Thanks for any ideas. Tom
 
A bad bearing and shaft on the main Hydraulic pump is my guess...the shaft gets a rough place on the peak of the lobe and will vibrate badly..
 
Are you talking the cast frame the pump is mounted to?
Broken cranks usually knock. Old harmonic balancers can
cause them to break.
I would disconnect the pump drive to see if that eliminates
the vibration.
 
I've got a '77 8430 that I replaced a hydraulic pump on a few years ago. It had some vibration in the cab around 1800-1900 engine RPM. While I had the pump off somebody suggested changing out the dampener on the front crank pulley. I did so and all cab vibration went away. Not saying that is your problem but if you have eliminated things such as the cab mounts and broken pump support it is something to look at. Any chance that mud got on the crank pulley and froze down affecting balance? By the way when I had the old dampener off it did not look "bad" nor did the local shop manager think that it was bad. I happened to ask someone that had a lot of time in the field working on those tractors.
 
That would explain the broken pump supports. I did have light vibration in the cab for a little while before my pump failed. The guy I talked to felt that any time those engines get past 5000 hours and you are in the neighborhood (doing work at the front of the engine) that it is best to change the dampener out for a new one.
 
Change the crank pully balancer. They fail ever so often. Should replace it at every overhaul .This can break the crankshaft . Also check the flywheel bolts if this doesn't do the job .
 
If you are right, pump could be uncoupled from eng and vibration would stop. That thing must really shake to break the cradle!
 
I have seen several of them break the pump frame,,and it was always the pump bearing that caused it.
 
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