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  1. #1
    New Member
    Join Date
    May 2010

    Default Questions on a 643 Bobcat

    I just bought a 643 Bobcat (diesel) and I have a few of questions. First, where is the best place to get a service manual? Is there only one service manual out there or is there one that is better than the other?

    Second, the machine is is real good shape and feels real tight still, but when I dig real had with it I have heard what sounds to be one of the chains ratcheting. Are there tensioners on these? Or would this just be due to a worn part? This is why I am looking for a service manual as I haven't even been able locate a schematic layout online for it so I can see how it's put together without tearing into it. You have to push it REAL hard to get it to ratchet...really almost abuse it, but I'd like to get it fixed before it gets worse or tears something else up.

    Last, what are you guys running for oil in these? I was planning to use Shell Rotella synthetic in the engine, not sure on the hydraulic or the final drive though...


    Attached Thumbnails Attached Thumbnails Questions on a 643 Bobcat-643_side_2-jpg  

  2. #2
    Gold Member
    Join Date
    May 2004
    SW of Minneapolis, MN
    2003 Kubota L3430 HSTC

    Default Re: Questions on a 643 Bobcat

    Best place to get a service manual is a Bobcat Dealer.
    Drive chains are case hardened, prestretched. There is no adjustment. It's highly unlikely that the chains would be "ratcheting" over the sprocket teeth. Use the bucket to lift the front wheels off the ground. Then rock the front tires. This will tell you how much "play" there might be.
    Your engine oil choice is fine. Hydraulic oil is "universal hydraulic fluid".
    Picture shows a very nice machine. The 643 was a light duty machine. Operated within it's parameters, this Bobcat will serve you well.


  3. #3
    New Member
    Join Date
    May 2010

    Default Re: Questions on a 643 Bobcat

    Thanks for the reply. I just ordered a manual from the dealer today. They are $85 from Tri-State in Burnsville which was cheaper than online.

    So what could I be hearing if the chain isn't ratcheting? Anything else come to mind? I guess I'll have to take a look at the manual and try to determine what may be the source of the noise...

    Yes, it is a pretty clean machine. It does have 5000+ hrs on it but the pumps feel good and strong, new tires, lifts, starts and runs good....


  4. #4
    New Member
    Join Date
    May 2010

    Default Re: Questions on a 643 Bobcat

    I checked the slack today and it feels pretty good. There is about 3/8" to 1/2" rotation at the top of the tire to take up the slack. With that, I'm not sure what may be making this noise. I checked the rear as well and the same thing.


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