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I need to replace all the bearing in the middle axle on a friend’s 2007 Polaris Sportsmen 500 6x6. The middle axle housing bearings blew up and both swing arm housing bearings were bad as well. The parts are on order and while I wait for them to come in I’ve noticed confusing information on the torque spec on the axle nuts in the service manual. First, the disk side axle nut torque is 120 ft. lbs. on the middle axle – this makes sense as it’s tightened against a normal ball bearing so you can torque all you want. The axle nut on the sprocket side states that an 8-10 ft. lbs torque is required. At first this made plenty of sense to me because the middle axle housing has tapered bearing (cone/cup) and like a trailer wheel bearing, too much torque will lead to bearing failure. Where the confusion started is when I looked at the rear housing axle torque specs. Both middle and rear housing have the same cone/cup tapered bearings yet the torque on the rear axle is 150 ft. lbs.! Why such a drastic variance in torque between both axles? Why 8-10 ft. lbs on the middle axle and 150 ft. lbs on the rear axle? Has anyone encountered this? This Polaris was serviced a year for chain and sprocket and now the bearings have blown up. Could the last mechanic have torqued the middle axle nut to over 100 ft lbs when only 8-10 ft lbs is required?



I hope someone can shed some on light on this.
 

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Welcome to the board!:med:
 

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Welcome to the forum!
 

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I'm really not familiar with the 6x6 models but I find it hard to believe there would be ANY fasteners on that machine that would torque to 150 ft/lbs. or even 120 ft/lbs. Around 80 to 90 is the norm on axle nuts.
Are you sure its not INCH POUNDS?? That would be about normal for tapper bearings after they're seated properly.
 

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Thanks everyone.

I've got the service manual and I'm seeing correct its ft lbs and 120 on the disk side 8-10 on the sprocket side for the middle axle and 150 for the rear axle.

I checked the manual for a 2003 Sportsman 400 that has a similar hub and that one calls for 8-10 ft lbs on the sprocket side, same as the middle axle on the 6x6.

If wonder if this is a service manual mistake as there are two axle nuts locked to each other. Perhaps the first one is to be torqued at 8-10 ft lbs and then you can lock the second nut to the first at 150. I don't know but I'll stick with the 8-10 ft lbs.

Thanks,

Pierre
 

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Just to avoid any confusion, the axle nut I'm talking about is the large 1 3/4" Nut that screws on to the axle up against the sprocket and bearings, not the axle nut at the end of the hub. This one is a crown nut with cotter pin and the torque specs on this is 80 ft lbs.

Thanks
 

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Ah Hah! Out of curiosity I looked at the microfiche for that machine and those axles are set up similar to a Scambler. Just a slightly snug light torque on the cone/taper bearings with a heavy torque on the jam nut. From what I see there are however some key differences between the middle and rear. The middle has nut retainers on each side to prevent them backing off (#2) when meshed up with the hub nuts (#5). And the left one will be pretty tight since it holds the brake hub and disc in place to align with the brake caliper properly. However, THIS side has no effect on taper bearing tightness as it simply holds the brake hub and disc in place. The The rear has only a snap ring on the left which is pulled against the bearing spacer (#2) by tightening the INNER axel nut on the right side and it is held in place ONLY by the outer jam nut....nothing else. (I usually add a little blue loctite)
You are correct that the taper bearings are only supposed to be slightly snug with the outer jam nuts torqued down to prevent loosening. You may also be correct that the last guy in there to replace sprockets didn't understand the difference and overtightened the bearings causing them to fail quickly. Sometimes the manuals aren't very clear and I've found many times that a particular section may have to read and reread several times to get the true meaning. Good luck and let us know how it goes.

Middle:


Rear:
 

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Thanks Polman500, I think you are bang on and this is the way I understand it. I will hopefully get all the parts by the weekend, assemble it and test drive. I will give an update when done. Thanks again for your help!

Pierre
 

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Got all the parts and finished the assembly. I ended up snugging the axle retaining nut on the sprocket side to about 8-10 lbs as per the manual and that looks good. Tested drove the bike and rechecked it. My buddy is all set and should be good for a while if he greases it regularly.

Thanks again Polman500 for your help.

Pierre
 

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Good to hear and you're very welcome Pierre. I think you pretty much already had it all figured out but I'm glad if my input was of any assistance. I'd keep a close check on it for the first little while just to be sure that everything is running in proper alignment and staying good and tight.
Good luck and keep the rubber down!
 
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