Combines variable speed main shaft

Yup. Problem is that big retaining nut on variator sheave on right side has responsibility of maintaining the preload on the mainshaft bearings. Believe this nut is torqued to approx. 350-400 ft. lbs. on the R52 and this should be checked quite often. When this bearing preload is lost due to nut losing torque, bearing fails and will break shaft usually where diameter is turned down. Gleaner changed this whole design in '01 with different shaft, bigger bearings, and new variator sheave that will maintain bearing preload without having to retorque nut over life of machine. If this happens again, I would upgrade to these new parts. Otherwise, check torque on nut every 50 hours and it will live.

exactly, I carry a baaw (big A$$ adjustable wrench) in the truck with a short handle sledge. It ain't scientific but a hitchup and a few slaps with the hammer on the handle will tell the tale in 15 seconds. Service has gone up to 600'n and still not stripped the nut off but 400 is all that is necessary. The bearing and sleeves at this torque become one with the shaft. When the torque backs off the shaft bends, the metal starts squeezing out from under the bearing, it gets hot and bam, the $ flow. Keep in mind there are 200 plus horses at work in a vertical load here; up to 330+ on a R72.

How about on a 94 R62IJ Just broke same shaft. Nut has been tightened over 600 ft. lbs. and checked frequently. last time it happened I remember someone said, something about an upgrade. Is it a bigger shaftIJ Bigger bearings, do you have to get new variable speed sheavesIJ Dealer didn't seem to know much at that time. Would anyone have part numbers for updateIJ It wasn't even working hard. 6-7 bu_acre beans is all we've cut all yr. Thanks.

sometimes stuff happens. I stated the nut had been tested to 600' ns . That was to see about the thread capacity. 600 would be a bit much. Around 450 is right. I hope I didn't mislead anyone. Simply look on prior and effective sn's and change the parts that are different if one wants to upgrade. I don't think there is a 'kit'. The bearings and bearing carriers and shaft are larger. As to why some have problems, even the sharpest service guys working with the engineering staff can't answer all the time. Bad material possiblyIJ We once had a crank break in a new truck engine - no reason$ ever found. Replacement ran for years. Something we always try to check is the torque sensing cams in the gearbox input sheave. If the belt slips and then grabs it is torque load city.

We have yet to pull a mainshaft from a R50 or R62-72. We have replaced the right hand and left hand bearings without removing shaft. Never any shaft damage because at predelivery the nuts or bolts that hold drives on get torqued. If the nut had been loose prior to you getting them tightened you may of well had erosion on hub or spacer which would prevent compression of inner race of bearing and hub assembly. If the hub or spacer eroded far enough the washer next to nut would bottom before you get compression on things thus repet failure. Another thing that can happen is hub seized to shaft over the years and tightening nut wasn't enough to move it tight against inner race of bearing. If you should have a repet failure of bearing be sure it slides freely in bearing holder and does not bind up when holder is tightened against side frame. I know they upgrade some of this stuff over time but alot of the time it is to make it more fool proof to factory worker and general repairman out in the field as far as torque ect. I'm unsure if your '94 has flat washer or cupped spacer next to nut but if it is washer you may be smart to remove nut to see if washer is bottomed against shoulder of shaft. It must have a gap to insure that hub ect. is getting scuished against inner race of bearing. Good luck.

Dan,I think you are very right about seeing to it the lock nut is putting a load on sheave and not just loading down against the shoulder next to spinned shaft. I replaced the bearings in my 52 and noticed the stationary half of the sheave(next to lock nut) of the variable drive would wooble alittle on the spinded shaft. If I remember right that sheave has to move on the spined shaft to torque down against everything else across the whole drive shaft. I think alot of these failures could be attributed to the lock nut bottoming before it presses the sheave into the rest of the stuff. I don't know why it happens either. To tighen mine up I used large machine washers that would clear the splinded shaft. And a NEW lock nut. I know the washers aren't OEM, any other ideasIJ Nick

likely nut was never tightened enough so hub started eroding next to bearing thus making hub shorter which caused washer to bottom on shaft before crimping things. Many of these failures take place after a bearing had failed thus one can figure that nut wasn't tightened after a repair. A bearing that has turned on shaft is likely not bearing problem but a clamp to shaft problem. If bearings are clamped to shaft and you have premature bearing failure it is likely that bearing holder is crooked to shaft putting load on balls or maybe installation process knocked seal partly off or completely off. We have very good luck with the bearing in that spot on the older combines like N7s (them bearings were smaller and N7s were 270hp) so I'm not so sure I would say the bearings are to small. One thing for sure is a big bearing is going to spin on shaft just as easy if things aren't torqued up properly. This is one thing that I have noticed Gleaner do over the years is if there is a failure from lack of torque or whatever they will change design even though original is just fine when assembled properly. The redesign is often to make it more fool proof during factory assembly and down the road after years of service.