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Thread: Cat 935C 1989: Three Issues: Engine Noise, No Forward or Reverse, Hyd Fluid Loss

  1. #1
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    Cat 935C 1989: Three Issues: Engine Noise, No Forward or Reverse, Hyd Fluid Loss

    Hi all:
    I'm new to heavy equipment, and bought the 935C two years ago to clear brush/dig basement/trenches on my small acreage. Finally started to use it this spring for about four hours, and issues have cropped up. Hope someone can provide advice:

    Engine: Starts and runs well at idle or fast. But...there is a very loud but random sharp metallic clank that sounds like a loose piece of sheet metal is being thrown about by a rotating mass. I thought it might be some sheet metal hitting the alternator belt/pulley and being thrown about, but everything appears tight under the hood. Could it be something loose in the muffler (outside has no rust), or, I hate to suggest, something in the engine itself such as broken rings or springs? Once engine is warm, the clank seems to die off. I also noted that when working hard pushing dirt, the black exhaust seems to come out through the front rather than the stack....

    Transmission: Two days ago, while pushing brush and dirt, I felt a bit of a shudder and within a few minutes there was no more forward or reverse--only a vibration in the floor pan when in gear. I was 300 ft into the bush from my staging area, and spent four hours clawing the machine backwards with the backhoe on a curvy path around big trees. I'm thinking stripped gears, but I hope someone has a less expensive diagnosis

    Hydraulic Fluid Loss: While dragging the machine out of the bush, the backhoe hydraulics were suddenly less than effective--stick and boom hardly worked, and I had to use the backhoe bucket to do the pulling. I soon discovered the fluid tank was very low. I haven't seen any major amounts of oil on the ground, but I have to admit I didn't check the reservoir prior to starting work--previous owner said all fluids were topped up and ready to go. I'll have to fill it and check for major leaks, but I would like someone who knows to confirm that the transmission and hydraulic fluids are not related on this machine....

    I have a service manual enroute, thanks to eBay, but all repairs will have to be done by real mechanic$ til I get a shop built on the property.

    Thanks for your advice!
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  2. #2
    Senior Member PAcattech's Avatar
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    Hi 4slice I think your first two problems are related I think the noise you were hearing may have been drive shaft failing and now that it wont move it has come apart. check between back of transmission and steering clutch case I'll bet you find its failed

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    I should mention that the clanking is there even when the transmission is in neutral. It seems to be coming from up front at the engine bay. But I'll start with checking the drive shaft as you suggest.

    Add'l details: Machine has 4200 hrs, with redone undercarriage.

    Thanks for your input.

  4. #4
    Senior Member Gavin84w's Avatar
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    I hate to say it but maybe she grabbed a piston skirt in that cold weather on start up. Hope you find something else though.

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    4slice, i have a 931b, you may have to look at droping the pan to get to the drive shaft unless you can do it from the top. could be the drive shaft banging around.
    Good looking Cat you have, hope that your problem is not to serious, let us know what you find out, good luck.

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    Does your fan shaft have any play in it? Might not be your problem but I wanted to mention it as my Deere back hoe had similar symptoms when cold. I'm not sure if the fan was actually hitting something but it was a loud metallic clanging noise. It may have been getting in some sort of oscillation until warming up.

    Where does your hydraulic pump get its drive from?

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    Gavin, the photo is from Dec 2010, shortly after it was delivered. The weather is spring-like now, thank goodness, lol. Wosama, thanks for the tip on dropping the pan. Old and Warn, I'll check the fan as well. I'm not familiar with the hydraulics/mechanics of the machine, yet, but I'll be reading the service manual cover to cover when it arrives! Thanks to all for your advice. I would like to get an idea of what's wrong before I take the $plunge$ on having a mobile service truck come from 60 miles away.

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    Hey 4slice, The drive shaft is only 8 or so inches long, you should be able to see it from the floor panel, also if you fire the motor back up, look at the exaust manu
    area to see if there are any leaks, and fan and head gasket area. Look carefully at the water and oil, good luck.

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    Wow, you guys are so Smrt! I talked to a heavy duty shop in town (only $95/hr + 1hr travel each way) vs. out of town Finning (only $200/hr + travel), and they suggested I call a guy whom they trust who does h/d repairs near my acreage (unk $/h, but no travel time), so that's a positive start. I'll call him this week...or maybe after next payday!

    In the meantime, I went back out there this afternoon to have a look, based on your collective thoughts:

    Engine noise: I should have looked harder for that loose sheet metal! The muffler appeared solid at first, but when one sticks one's neck into the engine bay, it was possible to see the top outlet of the muffler was rusted and loose, hence the random clanking. That really beats an internal engine noise

    Transmission: I lifted the floor panel to try to see the driveshaft. I put it in forward, then reverse, and things didn't look quite right.... The transmission output was turning, but the shaft was jumping and skipping over the u-joint. It looked ugly, so I put my digital camera in there, and have attached the photo. So, thanks to you guys, I have the diagnosis!!

    Hydraulic Fluid Loss: This one is still not solved, but based on the amount of fresh fluid in and around the driveshaft area, I wonder if the shaft has struck hydraulic tubing, causing a leak. I moved the Cat forward with the backhoe bucket, and found a one foot diameter oil spot on the ground (who knows how much the soil absorbed). So, I guess when the driveshaft gets fixed, I'll have the tech check for the leak(s) in that area.

    I have another question about the backhoe attachment, but I'll put that in a separate thread.

    Thanks again for everyone's sage advice. And Gavin made me feel guilty about using a winter photo of the machine, so I took a more seasonal shot tonight as the sun was setting.Name:  DSCF2718Edited.JPG
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    Senior Member spitzair's Avatar
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    Looking at the oil around the drive shaft it seems highly possible that your hydraulic leak is coming from there somewhere... Hopefully you'll get it sorted out without breaking the bank!

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    Thanks spitzair. I'll be consulting tomorrow with my neighbour next to the acreage. He has a gravel pit and lots of h/d equipment, so he can give me some idea of how big a job this will be. No doubt he could do this repair for me as he has a shop for his own repairs, but I've imposed on him too much over the last couple of years to even ask. He'll know the local guy that the h/d shop recommended, so I can get his opinion on who should do the repair.

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