JackShaft & Bearing Problems

If you are feeling it mainly on the left side I would eyeball the clutch side drive shaft bearing also. I have seen a few where the bearing had seized and wore out the the aluminum end stub of the driveshaft. If it is thumping as you describe it, that would be my first look. While it is in the shop, I would also check the jackshaft to bearing fit on both sides and check the torque on the QD sprocket fasteners. The top jackshaft bearing behind the brake is also a known problem if the sprocket fasteners are not checked and torqued adequately. hope this is helpful and enjoy the rest of your winter.

Have seen one shaft failure on the mag side on a 2013 Pro Rmk, probably because off a bad bearing, ended up had to change a QD belt, bearing and shaft.

sled

There is a recall that the quick drive bolts could come loose and damage the jack shaft, if the shaft is still good, replace bolts and toque to 45

Just took mine in for new bolts on quick drive and they found my jack shaft was bad!!

for those that have had problems... can you post up pics of your damages and remedy process for us to see and 'wrap our heads around'

Thx.



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Is there any reason why polaris doesn't have the jackshaft bottom out on the inner part of the upper chaincase bearing? On my last couple of builds I have moved the pto side outward to allow the shaft to side to the mag side a smidge so it bottoms out on the chaincase bearing so when you put the rotor and such back on it squeezes the bearing vs side loading the pto bearing? I've heard of a few sleds that this bearing(upper chaincase) was spinning in the shaft. Rental place that was having this issue was loctiteing the bearing. I don't think the bearing was spinning on the shaft but i think the bearing was going out first locking up and then spinning on the shaft. Maybe from to tight of a belt drive????

From before if it helps.So I lost my first day of sleddin because of this thread lol.

I pulled my drive system apart ('bin thinking about grease at 850 miles anyway and I wanted to find out why my top pulley bolt doesn't stay torqued). First I want to say, everytime I get into this Poo I am impressed with the quality of parts and excellent design.
Every bearing is NTN from Japan (and standard sizes). The jackshaft is light (with quite a lot of work in it's design) and very strong. Those 2 things alone are much different from my last sled.
To pull it apart was as simple as take off both belts, the secondary, and 3 bolts for the clutch side bearing cup and out it came. Doesn't get any simpler. Under 30 min. first attempt.
I even found a piece (the 3 nuts attached to a bracket for the bearing cup thingy) where Poo welded steel to aluminum lol. How do they do that?

Here's what I found.
First, I removed the belts, pulley and secondary. I thought i noticed a bit of a "sprong" as I unbolted the pulley so I kept that in the back of my mind. I spun the jackshaft and it was a smooth as silk. I might not even grease it I thought.
Then i pulled off my glasses and had a closer look and I saw the jackshaft spinning but not the bearing (QD side). Hmm.
Started poking in deeper and found a couple of little concerns. First the top of the "QD plate" is not very rigid on it's own. It needs to be torqued sold to the jackshaft to have any strength.
Second, on mine I needed to push in quite a bit to get the bearing to bottom on the machined bearing stop on the jackshaft. This design needs the inner bearing race to be secured to the jackshaft through torque on the ends or the shaft will spin and not the bearing.
Third, I think Poo's glue guns are getting old. My QD plate is unglued in spots and the glue feels like old gum. I looked at the bolt design and figure it will be a summer project to reglue. Not concerned at this point in time.

So I pull the jackshaft to look for galling on the shaft or bearing. Found a bit of discoloration on both. Bearing showed it had been secured slightly cocked for the last bit of time. Micrometered both and compared to a new 6205 I have in stock lol. Not enough difference for me to measure but there is no interference fit here. They are both (jackshaft OD and bearing ID) equal as close as I can measure (1/2 thouish).
I did retorque my top pulley bolt twice (once about 150 miles and once around 300 miles) and I do believe if i had not done this I would have seen extensive galling on the shaft.

So proceded to reassemble with a bit of "blueprinting". The bearing looked and felt fine. Maybe a C3 clearance now lol but I just regreased and left it.
I needed to make a 55 thou. shim for the jackshft to fit my QD plate position. I could have shimed either end of the shaft but picked the QD side. It has to be a special "homemade" shim because of the large radius at the bearing stop. So I chucked up a "close" shim and lathed it to fit.
Now when I bolted in my jackshaft it just touched the QD plate bearing as that plate fits in my sled BEFORE torquing up the pulley bolt.
I cleaned the surfaces and re-assembled using sleeve retainer high heat locktite between the bearing and the shaft and retorgued it to a tight position using some sleeves and a bolt to let it set. I don't know if this is necessary but it made me feel better lol.

Then I took my glasses off again to see why this happened on my sled. Many systems use the torque on the inner race to lock in the bearing. Nothing wrong with that but it cannot lose it's torque.
What I found with mine was the disc brake (it`s the sleeve-spacer between the bearing and pulley also) slowly had ever so slightly been mushrooming into the bearing. You could just see and feel the radius of the inner bearing race on that side. So even though it was only a 1/8th turn of lost torque it is enough to allow the shaft to spin in the bearing. You could also see movement had been happening on the wave washer and pulley surfaces the disc and washer contact.
I centered the disc on the splines and lathed off .60 thou. off the bearing side and 30 off the pulley side and replaced these distances with shims. This gives me much more contact surface to torque against the bearing. I also replaced the wave washer with a thicker flat washer so I could see if it comes loose easier and give me more contact surface to torque against too.

IMO Poo could improve this area with a few simple changes. Add a thou to the OD of the jackshaft, a little stronger plate or a couple of fasteners at the top of the tunnel, maybe a little handfitting in this area to shim jackshafts during production lol, better controls on the glue guys lol, or two birds with one stone; Make a hardened sleeve to fit between the bearing and pulley and let the disc FLOAT on that sleeve.

Moral of this story; check your top pulley bolts boys. Check them twice.

I guess the questions i still have is if they are still not bottoming out the jackshaft on the backside if the upper chaincase bearing the you can tourque all you want all your going to do is side load the clutch side bearing and wear that one out prematurely. Did you get to see the bearing? Was this the chaincase bearing?

I am wondering, because the bolts have locktite on them, it is a problem to simply check them for torque, or do you have to pull out the bolt, put new blue loctite on, and then retorque, every time you check it?

Hopfarmer said:

So long story short......after some run around. Dealer replaced jackshaft and bearings. Quoting a jackshaft update was needed. The tech that worked on my sled said the shaft had spun inside the bearing. Hence the need to check the upper pulley bolt for proper torque spec before each ride.

1. Gas -- Check
2. Oil ---- Check
3. Gear---Check
4. Upper Pulley Bolt--- Good thing I just bought a new torque wrench.
5. Driveshaft ---Check

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Fixed it for you.

This is what it looks like if you feel the thumping under your left foot. Mine did it from day 1.

In that second picture, is that brown from heat or is that rust on the bearing???
Thanks

It's the dust cap

The rest of the black around the seal is grease??. Just looking at the picture it does look like rust.

COP-OUT said:

The rest of the black around the seal is grease??. Just looking at the picture it does look like rust.

Click to expand...

no, its aluminum shavings...

Pro in our group on Sunday lost another QD belt....upon closer inspection it was caused by a junked driveshaft bearing, apparently allowing slack in the belt. Not sure which side. A little over 500 miles on the sled, meticulously maintained.

yooper I was wondering if the bolt was a better, stronger bolt too or just that they wan't a good set from the loctite. The factory just puts loctite on the bolt and lets it dry so it's probably a way better hold the first time it is used. If you don't get a new bolt I would clean the old one, apply the loctite(not sure which brand but I thing its yellow when dry) and let it dry then torque it.

Just took mine out and put RED loctite on it. Hoping im right, but cant possibly imagine a bolt sheer on a part with that little strain on it failing without first loosening up first.