Go Bottom790 snow blower vibration
 | xxxx
Join Date: Feb 2002 Posts: 1 Big Rapids, MI 
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2001-12-03 33640
I just purchased a new John Deere front mount snowblower for my JD 790. It has a bad vibration from the PTO drive shaft to the blower, dealer says it is normal. Does anybody have a similar problem, I'm wondering if it exists on the 4000 series compact J D tractors? My PTO shaft is triangular shaped and the 4000 series shaft is round????
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2001-12-04 33649
I don't know if a manual for the pto shaft was supplied with the blower. If there is a manual, it probably gives maximum angles and distances of operation. If the mounting of the shaft is such that max or distances are approached, then there may be noticeable vibration. It's possible that another make of shaft would have wider allowable specs and would produce less vibration. However, it could be kind of tricky to introduce this sort of idea to a dealer and retain a constructive working relationship--just claim to be extra particular I guess.
If the shaft is a Comer (I think that's the spelling), it's an EU import and the maintenance instructions aren't exactly clear even with a manual. I find the standard EU manuals in a dozen languages or so are not very illuminating. The basic idea is that most fittings and the grooves the end shields ride in are to be greased every eight hours. The shaft itself and the shear collar or faces are lubricated every 16 hours.
The shaft is disassembled by turning plastic screw heads on the end shields 90-degrees and pulling out the screws. The end shields are mounted on a plastic collar that rides in grooves on the ends of the shaft shield. The collars appear solid but aren't. There's a split, and the collars are removed by just pulling them open. This little blurb might save some time and aggravation if shaft maintenance hasn't been done before. Oh yes, I 'm not absolutely certain, but there's a change the triangular shafts are not symmetrical, and they may go back together only in one orientation. That could save even more aggravation.
....
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 | Murf
Join Date: Dec 1999 Posts: 7249 Toronto Area, Ontario, Canada
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2001-12-04 33650
I would also sugest that you verify that it is indeed the drive shaft that is vibrating. Snowblowers, tillers and flail-hammer (Mottt) mowers are notorious for their ability to shake. The vibration is usually caused by the units internal drive system and not the pto shaft. Because of the routing of the driveline, it must change direction once, and be offset several times, this offset, from the output shaft of the gearbox, down through a chain to the auger shaft must be tensioned to prevent the chain from 'slapping', this is normally accomplished by pads or idler pulleys mounted on arms, which are held against the chain by springs. If there is no load, or a varying load you will get vibration until the load, and therefore the spring tension settles down and arm quits moving. I would not be concerned about vibration unless it happens constantly and uniformly under all circumstances. Best of luck. ....
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| Paul_in_NS
Join Date: Jul 2003 Posts: 7 Halifax, Nova Scotia
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2003-01-03 46896
I have a JD855 with the JD 2 stage snowblower. I had a bad vibration in the triangular drive shaft the first time out this winter. The problem was in the mid-shaft bracket between the main drive shaft and the gearbox drive shaft. One of the bolt heads was sheared off and the mid-shaft bracket was moving around and setting up quite a resonance in the main shaft. I picked up a large rock last winter and broke several parts in the drive train but I must have missed the bolt in the rebuild (or it didn't give up the ghost until I used it this year). Anyway, since your unit is new it is not likely sheared but the mid-shaft mounting may not be tight. You might want to check it.
Paul ....
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