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  1. #11

    Default Re: JD 790 Front Axel

    Well I jacked it up last night and I noticed that turning the front wheels by hand the left side one would stop at a certain point. So took it all apart and the lower pinion gear and the large gear the connects directly to the wheel were missing teeth. Since they are really pressed on I had to take it to the dealer to have them change the gears out for me. Thanks for all the help!

  2. #12
    Super Star Member RoyJackson's Avatar
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    Bethel, Vermont
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    John Deere 4400 MFWD, Deere 855D UTV, Z920A Zero Turn Mower and assorted implements

    Default Re: JD 790 Front Axel

    Quote Originally Posted by arrabil View Post
    Its possible the noise only happens in 2wd because the gear teeth aren't under load so they have lots of play and can bang around. While in 4wd they are loaded and have less give to them to make noise.


    Roy, when you say the reverse is weaker than the forward, do you mean because running the ring gear on the coast side of the teeth is inherently 20% or so weaker than running the drive side or is there some other design feature that makes it weaker?
    I am no gear design expert by far...let's get that out of the way.

    Gears can be designed to bear more load in the driven direction (in the case of the tractor, the "driven direction" is normally forward...but when I write "driven direction", this would be the side of the teeth that mesh first. The design considerations may be the root radius (radius at the bottom of the teeth) or how the teeth are heat treated or the actual angle of the "front" face (side that meshes first) of the tooth vs. the "rear" of the tooth.
    Also, the backlash is set to the "front" face. An improperly set back lash can be make the "clunk" noise or a whine. Improperly set backlash can also result in premature wear.
    I've not had to do any major maintenance on my 790 (thank goodness) and I'm not really set up to do this kind of work any more. But over the last 30 years, I've done enough (as an amatuer...I'm way too slow to make any money at this kind of work) to be reasonably capable.
    Roy Jackson

    "Any government that does not trust its citizens with firearms is either a tyranny, or planning to become one."
    -Joseph P. Martino

  3. #13
    Veteran Member
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    Winterstown, PA
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    JD 4200 & X475

    Default Re: JD 790 Front Axel

    I gotchya. the front of the tooth is called the "drive" and the rear is called the "coast." Backlash is inherently the same on both sides of the tooth. I've done my share of gear setups.....

    I find it interesting that the ring gear would break before the transmission while doing hard work in reverse. Speaks well of the quality of JD's transmissions. I wonder if its designed that way on purpose? Break the easier to get to parts before the hard to get to ones?
    JD 4200 w/ 420 Loader, 8B Backhoe, 59" Snow Blower
    JD X475 w/ 54C Deck & 3-Bag Power Flow

    Looking for an engine out of a JD 4300/4310/4400/4410. Send a PM if you have one (or a parts tractor).

  4. #14
    Super Star Member RoyJackson's Avatar
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    Default Re: JD 790 Front Axel

    Quote Originally Posted by arrabil View Post
    I find it interesting that the ring gear would break before the transmission while doing hard work in reverse. Speaks well of the quality of JD's transmissions. I wonder if its designed that way on purpose? Break the easier to get to parts before the hard to get to ones?
    I think Deere expects the tractor to do the majority of it's hard work going forward.
    As far as being designed that way on purpose...good question. I have no idea. I think the first consideration is cost of manufacture.
    Roy Jackson

    "Any government that does not trust its citizens with firearms is either a tyranny, or planning to become one."
    -Joseph P. Martino

  5. #15
    Veteran Member
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    JD 4200 & X475

    Default Re: JD 790 Front Axel

    Yeah probably. I'm as cynical about it as anyone but you gotta figure there are some engineers in the design office thinking about doing it "right" too. At least I hope so. Certainly I buy JD because I believe they are built and designed better.

    On second thought though... backwards, uphill, with a heavy load, turns the front axle into the drive axle on its weakest side. Probably does stress it past any design considerations. They do make the rear axle the strongest on pretty much all vehicles for a reason and this would be it.

    berkompt, if it makes you feel any better, before hour ten of owning my tractor I put a stick through the radiator because I didn't know you shouldn't keep going back and forth over them... sooner or later one will pop up and nail something important. The hard way always teaches best.
    JD 4200 w/ 420 Loader, 8B Backhoe, 59" Snow Blower
    JD X475 w/ 54C Deck & 3-Bag Power Flow

    Looking for an engine out of a JD 4300/4310/4400/4410. Send a PM if you have one (or a parts tractor).

  6. #16

    Default Re: JD 790 Front Axel

    I can't believe it I just got the one side fixed for $600 and now the other side is broken.

  7. #17
    New Member
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    Nov 2010
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    John Deere 790

    Default Re: JD 790 Front Axel

    We have had a 790 for 3 years, the front axle issues you are experiencing has occured 3 times to us. It has to do with the berings and gears. Each time John Deere has replaced the parts under warrenty and each time it was on the right side. Three weeks ago my tractor broke in half from simply picking up a load of dirt. John Deere does not stand by their product. We struggled to keep the tractor and our small family business has now failed because we owe on a tractor that is useless. John Deere out right said we pulled the tractor apart... My advice.. buy a FORD!

  8. #18

    Default Re: JD 790 Front Axel

    Have been working with the compacts and I see that a lot of the 790 users aren't using enough ballast...say loaded rear tires and weight box like JD says...so they are taking out their front ends. Without a lot of ballast you are overloading the front end and they cannot withstand this. Also constant use in 4WD heavy turning etc will all waiste them. The 4x4 is an assists arrangment. I don't think the 790 is a very good loader tractor as the front is a little light from the factory. Nice small tractor but it needs a smaller loader and sensitive care. Go on up the higher series for your loader tractors.

  9. #19
    Silver Member
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    Stewartstown, PA
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    JohnDeere 2720

    Default Re: JD 790 Front Axel

    Quote Originally Posted by Tractor King View Post
    Have been working with the compacts and I see that a lot of the 790 users aren't using enough ballast...say loaded rear tires and weight box like JD says...so they are taking out their front ends. Without a lot of ballast you are overloading the front end and they cannot withstand this. Also constant use in 4WD heavy turning etc will all waiste them. The 4x4 is an assists arrangment. I don't think the 790 is a very good loader tractor as the front is a little light from the factory. Nice small tractor but it needs a smaller loader and sensitive care. Go on up the higher series for your loader tractors.
    By higher series....do you simply mean larger tractor? Are you aware of this issue with say the 2305 or the 2X20 series?

  10. #20

    Default Re: JD 790 Front Axel

    John Deere beefed up the pump on the 790 and used the 5' bucket and a heavy loader. End result self destruction. I have a JD4400 and it has twice the front end of the 790. The 790 was built on the 670 frame. Just not a loader tractor. Look at the front axle housing...they look at their small size.

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