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  1. #1
    Platinum Member
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    Feb 2005
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    972
    Location
    Central WI

    Default 3720 MFWD issues

    Today my 3720 started making clunking noises when changing directions. It only does it in 4wd and only seems to do it when the initial load is applied. The front wheels do appear to drive. I looked at the front driveshaft (unimpressive to say the least) but couldn't see any glaring issues. The dry splines and floating/roll pinned collars on the shaft have me scratching my head.

    At any rate has anybody had any diff/driveshaft issues?

    I should add that the sound seems to border on a clunk and a pop and seems to change where it is coming from. Some times it seems to be up under the front diff and other times it sounds like it's midship.
    JD3720 300CX FEL, 48" forks, MX-5, RB1172, BB1172 air seat susp
    JD 455 2 wheel steer
    JD x750-Auto Connect w/60" HC deck

  2. #2
    Gold Member Glen Watkins's Avatar
    Join Date
    Dec 2009
    Posts
    490
    Location
    Finger Lakes Region of New Yorkistan FUAC
    Tractor
    2007 John Deere 4320 Cab Tractor

    Default Re: 3720 MFWD issues

    Make sure your wheels lugs are all tight!
    JD 4320 Cab,6' KK Brush Hog{Old Heavy Version}, 6' Woods Finish Mower, 400x FEL 73" HD Bucket, 3rd Function Kit Installed, 6' AF11 Snow Blade, 60" Root Rake Grapple, Wallenstein FX-90 Skidding Winch...

  3. #3
    Platinum Member
    Join Date
    Feb 2005
    Posts
    972
    Location
    Central WI

    Default Re: 3720 MFWD issues

    Well I think it's the driveshaft splines. I did not get a chance to study thoroughly, but it's not very impressive. There are at least 2 short splined couplings. The rearward one is pinned with a roll pin. The front one slides free or at least mine does. All I did was slide it around a bunch trying to see what movement was allowed. These splines really should be lubed in my opinion.

    Anyhow, I went to do a different task and tried it and it worked fine.

    I have to say, the front PTO shaft setup on my 455 is more robust that this spindly little thing...
    JD3720 300CX FEL, 48" forks, MX-5, RB1172, BB1172 air seat susp
    JD 455 2 wheel steer
    JD x750-Auto Connect w/60" HC deck

  4. #4
    Platinum Member
    Join Date
    Feb 2005
    Posts
    972
    Location
    Central WI

    Default Re: 3720 MFWD issues

    What I have learned so far is that both of these splined couplers are supposed to be pinned. My forward one is not. probably won't get to lok at this for a week or so, but I have a coupler and pins coming. from what I see i would highly recommend disassembly and greasing on these with a super good moly grease like Cenpeco Mega Moly.
    JD3720 300CX FEL, 48" forks, MX-5, RB1172, BB1172 air seat susp
    JD 455 2 wheel steer
    JD x750-Auto Connect w/60" HC deck

  5. #5
    Elite Member AKfish's Avatar
    Join Date
    Oct 2004
    Posts
    4,986
    Location
    Kasilof, Alaska
    Tractor
    JD 5075M; JD 110 TLB; Ford Ferguson 9N: JD X300R

    Default Re: 3720 MFWD issues

    For what it's worth - the front driveline on my 110TLB is pretty "spindly", too! And the front collar joint is pinned with a roll-pin as well.

    Have never heard of anyone twisting or breaking the collared joints, though.

    Since the shaft does not slide back and forth with any up and down motion - the front axle and transmission are solidly fixed - and the distance does not change; grease would only help to deter corrosion.

    I would be more concerned with possible damage to the front axle hub.

    AKfish
    "Most people want to live on top of the mountain, but all the happiness and growth occurs while you're climbing it."

  6. #6
    Bronze Member toolbox5's Avatar
    Join Date
    Mar 2010
    Posts
    88
    Location
    Ripley , NY
    Tractor
    John Deere 3120,214,L105

    Default Re: 3720 MFWD issues

    did you try checking your front axel thrust bolt, my tractor did that and once i retorqued it and it stoped specs are in owners manual , might help

  7. #7
    Platinum Member
    Join Date
    Feb 2005
    Posts
    972
    Location
    Central WI

    Default Re: 3720 MFWD issues

    OK I had to take it apart as it started jumping splines again. The frontmost coupling splines are severely worn as are the pinion splines as well. The others are just fine. For the moment I flipped the coupling iuntil I can get a new one. The roll pin is just in the coupling and used to limit floating.

    My advice to all is to pull this shaft down and grease the splines before it makes a mess.

    Pop the roll pin out of the rear coupler and slide it rearward. then slide the front coupler all the way forward and the shaft will fall on your head. Thankfully it's light and my head/ear are tough...
    JD3720 300CX FEL, 48" forks, MX-5, RB1172, BB1172 air seat susp
    JD 455 2 wheel steer
    JD x750-Auto Connect w/60" HC deck

  8. #8
    Gold Member
    Join Date
    Oct 2000
    Posts
    412
    Location
    NH
    Tractor
    John Deere 3720 Cab Tractor

    Default

    I'm having the same issues right now. I'm hoping it isn't the cable that controls the movement of the shaft with the lever.

    I can put the shaft into 4WD mode by hand, but it won't stay in 4wd mode. The shaft jostles free after using it for a few seconds.

    I am really puzzled, because it looks like the roll pins are in place on both couplers.

    Any ideas?

    It doesn't look like my splines are worn too badly.

  9. #9
    Gold Member
    Join Date
    Oct 2000
    Posts
    412
    Location
    NH
    Tractor
    John Deere 3720 Cab Tractor

    Default

    I would send it to dealer, but I'm afraid once it is there, It will snow, and I'll have nothing to use.

  10. #10
    Banned
    Join Date
    Feb 2013
    Posts
    101
    Location
    east coast
    Tractor
    2012 JD 3720 deluxe cab

    Default Re: 3720 MFWD issues

    I dont remeber the torque spec but it is in the manual. These bolts seem to be very loose on all machines from the factory. Check it out.

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