Gearbox backlash

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Gearbox backlash

Postby TractorTed » 13 Jan 2021, 19:28

Hi, I've got an old Permobil chair, and am getting increasing amounts of clunky backlash in the drive on both sides. Not a showstopper but pretty annoying.

I'm pretty sure it's coming from the gearbox rather than anything else. After googling the model number it seems to be a GB9 Parvalux unit. Anyone else ever had issues with Parvalux gearboxes? Are they prone to this, or do I just abuse the chair too much? I have been known to bump it up kerbs when it's in the mood :lol:

Cheers, Ted
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Re: Gearbox backlash

Postby woodygb » 13 Jan 2021, 19:33

Have you checked for slop caused by wear on the wheels keyway ?
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Re: Gearbox backlash

Postby TractorTed » 13 Jan 2021, 20:01

The keyway does look a little worn, but I think the slop is coming from the gearbox internally. Need to crack it open I guess. Is this a common problem? I'm just thinking I don't really want to replace the gearboxes only for the same to happen again..... If there's a better gearbox out there, I'm not averse to a bit of tinkering to make it fit!
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Re: Gearbox backlash

Postby duke1 » 13 Jan 2021, 21:13

TractorTed wrote:The keyway does look a little worn, but I think the slop is coming from the gearbox internally. Need to crack it open I guess. Is this a common problem? I'm just thinking I don't really want to replace the gearboxes only for the same to happen again..... If there's a better gearbox out there, I'm not averse to a bit of tinkering to make it fit!

hi i have had some experience now restoring several different types of wheelchair gearboxes and can say that it is possible if the wear is not very bad and gears still have all there teeth in fair condition it is fairly easy to tell when bearings have play and 2-6 motors ive done worked well and had a lot less slop in the mechanism and run very much quieter.
i purchased a cheap bearing removing puller kit and have a vice and power etc so can easy remove bearing without damage to gears,but tbh you be far better finding new or little used ones and if you restore the old ones they are best kept as spares for emergency use,also depending on design some or rather most modern chairs use a cush drive from gearbox to motor which do wear out and can be noisey but theres mends for them @burgerman has a thread here somewhere showing a better fix for them.
do not dismiss used from reputable seller but be careful as some of the smaller private ebay mobility parts sellers have little or no idea what there selling and how to correctly describe the true condition.
i speak from personal experience there after getting 2 very worn and noisey misdescribed puma 40 6mph motors,got my money back though.
so when it came to my tinas favorite but 40 odd year old chair with axial motors that are rarer than the fabled hens teeth got backlash and noise i stripped and replaced the set of bearings cleaned and lubed with new seals and there good and quiet and smooth now,but this was done before things got damaged ie gear cogs and shafts as these are nearly an impossible buy new.
goodluck
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