I just finished replacing all the bearings in the gearbox on a 96. It had a very loud high pitch bearing noise when the job came in. I have no specs on the box. I miced the shafts, and the freewheeling gears. I did the math with the specs of the new caged needle bearings (oe), and seemed to be in good shape. Everything looked to be in good shape, except for 3 of the open ball bearings. I did every bearing. I figure if your in there, might as well do it all the way. I replaced all the oe (KBC) with a higher quality *** bearings. Pre-lubed all the bearings with Polaris syn gear lube, and filled the unit with the same. I fired it up ( while on the lift) and popped it into high, gave it some gas, and just about died. Almost no change in the noise. I've done a bunch of boxes of this type, and never had any problems. What did I miss? With a stethascope, I checked, and the noise is in the box. When the guy purchased the machine, the seller told him this was a normal Polaris noise. I've only worked on 2 other Polaris ATVs, and can't remember them sounding like an Italian sports car. Not having specs, may have bit me in the butt.
Anybody ever run into this problem. Anybody have specs on this unit?
Bad day!

Pete

 

Well, Simple things first....
Output shaft support bearing ok??? Try disconnecting the drive chains and run it again. Try taking the drive belt off of it and spinning the input shaft and feeling for "notchiness".. Usually, a high pitched whine is a bearing means that the preload isn't right... just some things to check..

 

The output shaft support has a bushing. I removed it and ran the machine, with no change. I was planing on pulling off the chain first thing Monday morning. When I first removed the secondary clutch, I had a little play at the input shaft, with notchieness. The other thing, is I'm not the first person thats been in this box. When I first tore it down, all but one bearing in the box were KBC. It had 1 SKS.It was on the input shaft at the closed side of the case. How do you preload the bearings on the unit? There were no shims under bearings,and all the washers whent back in to the unit in the same places they were removed from. If the last guy put together wrong, I just followed the tail lights of the road in the fog. I'll eat the labor time to take the unit out if I have to, and find the problem, and I could use all the help I can get. I would never even think of giving the machine to the guy the way it is. It also seems to have less noise in low range, so I was thinking the inner surface of the high range free wheeling gear is too worn, giving an un-even load on the caged needle bearing. It also seems to lessen at higher speeds.
Thanks for the help Mudmachine, any more is very welcome.
Pete

 

What oil are you running in it???.. I usually put Mobil 1 Synthetic gear lube in them... It seems to protect better than the Polaris stuff...
Does the sound get better/worse as you load or strain the drivetrain?... What brand of drivebelt is on it?. (belts whine sometimes)
Another thing, remove the belt, run the engine up to WOT, and part throttle and hold it....
The Polaris 2-strokes seem to have a significant amount of "whine" by themselves... That could also rule out any primary clutch noise being transmitted to the transmission via the belt...
I know how ya feel, Sometimes youre the hunter, and sometimes you end up the hunted....
Good Luck..

 

I envy the owner of that thing. I've always wanted a screamer!
Although I have never worked on a Polaris, I have worked on numerous snowmobiles with a similar clutch set-up. I would imagine that,like a snowmobile, the primary and secondary clutches have to be properly aligned. Both the center-to-center distance and the clutch offset have to be right. Otherwise the clutch action and belt life will be compromised. The noise you are hearing could be the drive belt begging for mercy.

 

I use the Polaris syn gearlube (purple stuff)which to me seems a bit to low in the viscosity dept. The belt is Polaris also. The way the box bolts in, they don't give you a lot in the way of alignment, but that's gonna be on the list Monday. There were 3 washers behind the secondary clutch (input shaft on trans), a thick spacer, and 2 thinner washers, so theres room to play with that alignment.
Thanks fellas, Mondays another day.
Pete