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Bought a 1986 430 last year, it's in good shape for age.The deck is free from damage or previous repairs...All summer it mowed about 3 acres with zero problems.. last week my wife said threw the deck belt..She removed the covers and put the belt back on...Today it lost the belt twice.The belt is a John Deere brand bought new this year...I took a look and all pulleys and bearings seem too spin fine without much excessive slop...The tension spring seemed a bit loose so I made a shorter rod and it tighted the belt better......Running the machine without the covers I can see the belt is vibrating badly, and perhaps that why the belt gets thrown...I jacked it up and checked the deck driveshaft...There's noticable play in the u-joint and the fit onto the drive spline is sloppy...Turning the center blade by hand, the blade moves a few inches before I feel resistence of the mower deck gear box...
What do you guys think about this? thanks
 

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Bought a 1986 430 last year, it's in good shape for age.The deck is free from damage or previous repairs...All summer it mowed about 3 acres with zero problems.. last week my wife said threw the deck belt..She removed the covers and put the belt back on...Today it lost the belt twice.The belt is a John Deere brand bought new this year...I took a look and all pulleys and bearings seem too spin fine without much excessive slop...The tension spring seemed a bit loose so I made a shorter rod and it tighted the belt better......Running the machine without the covers I can see the belt is vibrating badly, and perhaps that why the belt gets thrown...I jacked it up and checked the deck driveshaft...There's noticable play in the u-joint and the fit onto the drive spline is sloppy...Turning the center blade by hand, the blade moves a few inches before I feel resistence of the mower deck gear box...
What do you guys think about this? thanks
It sounds like the gearbox is due for a rebuild.
 

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Thanks...I also think new u joints and driveshaft because the slip joint is quite worn...My wife does most of the mowing and just loves the 430 with it's smooth running engine and tight turning...
 

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Truckedup,

Replacing the bearings and seals in the gearbox is not a complicated affair. I rebuilt the bearings, seals and the input shaft for about $150 in parts. I agree with you that replacing u joints would be worthwhile. The driveshaft not so much, mostly due to the cost for a driveshaft.

I had a problem with mine that it would break that big heavy belt. It turned out that the idler pulley and bearing needed to be replaced. That may be the source of the vibration you are seeing. I would also replace the plastic bushing at the pivot end of the idler arm.

Dave
 

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When you remove the gear box you might find the pulley to be very loose. It may have worn the roll pin hole and keyway to create a lot of slop. Hopefully the shaft is not worn. Just something else to check out.

tommyhawk
 

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Thanks for the tips....I mentioned the driveshaft slip yokes and U joints are worn...I pulled the shaft apart just to grease the joints better to to get a few more hours use...Putting it back together I made the sure the shaft was phased properly...I did not check shaft phasing before I pulled it apart, damn....maybe it was out of phase and it took a while to start throwing the belt...But most likley it's needs some care.I will check it today.....No problem ,the mowing season is nearly finished around here..
 

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Discussion Starter #7
Photo of the deck in my other thread....I dissassembled the gearbox....It had reasonably clean oil, gears and bearings look in great shape.No slop in the bearings, slight bit of preload .The drive gear has a slight amount back and forth play and the key is slightly worn but the keyways are fine...Deck blade bearings spin smooth and one end bearing has just slight up and down play.. The idler has about 3/16 play measured at the pulley edge....
The drive shaft slip joint and u joints are worn but like they are falling apart...The splined release collar is worn, has some ply on the splined jackshaft...
If this were a a vehicle driveshaft, I would replace it...It seems they are quite expensive ..FT Wayne clutch sells what appears to be an improved shaft for a bit less than the JD type...
 

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On my 420 the idler pulley wasn't level. The area where it mounted got weak and would flex and throw the belt. When it throws it make sure all the pulleys are level. I took the pulley off and welded a support piece in there and never had another problem. good luck
 

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Good point about the idler/tensioner pulley. Mine didn't throw the belt but the steel sleeve over the bolt was worn and the plastic bushings inside the arm were all but gone. Deck metal was solid but I did add a larger, thicker washer on the bottom. Think a longer bolt was necessary then, but I don't remember for sure. Did have to replace the pulley on the gearbox. $$$

Oh yeah, when you replace the spring and hook, be sure it is hooked in the arm so it does not rub on the gearbox pulley hub.

My deck is older but same belt routing. Here's some pics of the spring and the extension hook in the hole in the arm. Guess who didn't pay attention when he took it apart. I just gotta do some things two or three times, I suppose.

IMG_3374.JPG

IMG_3375.JPG

IMG_3365.JPG

In this pic I had the hook going through the wrong direction in the arm. Found out after installing the gearbox and slipped the belt over the tensioner pulley. The rod was touching the pulley hub. Yours might clear either way, but check it out.
IMG_3362.JPG

tommyhawk
 

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When the belt comes off the gearbox pulley is still turning and will wear a spot in the belt. It happened to me last year and I ruined a brand new $70 belt before I heard the different sound and turned the pto off. I ran it for a little while but it produced a rhythmic thumping and the belt flapped badly.


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Discussion Starter #11
All the pulleys including the idler seem to be the same height, well, within 1/16 inch....Interesting story about the belt with the wear spot flapping and vibrating because that is exactly what mine is doing...I checked over the belt very carefully just now and don't see or feel any worn areas...But considering nothing else seems bad enough to cause a problem, and it mowed just fine all spring and summmer...Maybe I just have to buy another brand new belt...:dunno:
 

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It's seems as good as new now....I replaced the mower drive drive belt with a non John Deere brand. A new idler tension spring. and the front PTO drive belts.One drive belt had much of the rubber chunked off, the other was cracked, very old...I disassembled the gear box ,seemed fine, replaced the seals......
Did about an hour of mowing...It runs smooth now, no belt flapping..I believe it was the deck drive belt and idler spring. The new John Deere brand sping is noticably stronger than the old one
 
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