<div class="FTQUOTE"><begin quote>Originally posted by: HIGHOCTANE

<div class="FTQUOTE"><begin quote>Originally posted by: DODGE57HEMI



Well the 4wheel drive system obviously works but common sense would tell you otherwise that someting is just not right with this situation. I know if it were on a regular vehicle like a Jeep there would be major issues LOL!</end quote></div>



Dodge..I watched the video..I agree if the wheel speed difference were that much on pavement it woud be very bad! There is no way that is the case.

That got me thinking. I really haven't looked into the front diff operation too much. So I dug out the service manual. I'm still studying it but so far it looks like the front axles are not positivley locked to the ring gear, they are connected by clutch packs and sort of an overrunning clutch assy. The way it is designed is that when on hard pack,or pavement,or anywhere there is enough traction to keep the rear from spinning the gearing is set up to keep the front axles turning faster than the ring gear carrier. The front is geared to turn a little slower than the rear. In otherwards the front axles overrun the the carrier and turn faster than the carrier as they spin the same speed as the rear wheels, and this is what keeps it out of AWD until the rear slips. Once the rear slips the front/pinion/ring gear carrier meets axle speed and engages and locks the front alxes to the ring gear carrier mechanically. No speed sensor or anything like that is used to determine wheel slippage(as I have seen some say) If the front and rear were geared the same it would constantly be in and out of AWD,even on solid ground. So with solid traction the fronts free spin and will not bind on pavement. So you can ride around all the time in 4wd(just like the manual says you can) other than possible wear and tear on the AWD coil. Must be why the Polaris doesn't have the caution about not riding on hard surfaces in 4wd huh?

Anther plus for Polaris AWD in my book...really the credit goes to Hilliard, Polaris is just smart enough to know a great system when they see it.</end quote></div>

That is some interesting design that Hilliard came up with but it does explain why sometimes it breaks the retaing cage inside the diff ( I think its the clutch pack retainer thoe not sure!) as when the front tire gets into a bind the clutch pack try's to catch up with the speed of the rear tires tearing up the cage! I have only read about this happening once or twice and it surly has not happend to mine but this would be my best guess as to what is going on inside the front diff!

Thanks for the info! It is a design that works and works great! It is deff hard to beat for auto locker!

 

Looking at it briefly I'd say the most likely way to break the cage would be roller mis-alignment. Debris in the fluid could do this IMO. If the rollers don't have a smooth surface to ride in they could be forced at an angle which would lead to one end engaging the cam(my term, it is actually the inside of the ring gear assembly that has a specific shape to trap the rollers and cause them to bind) and further turning the roller out of alignment breaking the cage. The rollers and cage are much like a tapered roller bearing without the taper,also there appears to be 2 rows of rollers. One for each axle? Also the cage is plastic..a steel cage may prevent this,or cause more destruction depending on why it is breaking to start with.
Another possiblility is roller and "cam" wear. As the roller and "cam" wears it could allow too much clearance which would allow the roller to engage too much which would actually jam the roller, causing a roller or rollers to stay engaged regardless of AWD coil position in some situations.

 

Is the your service manual for the 850 or you older 800?

 

The manual I am referring to is for the 08 700/800,but most of the front diff parts are interchangeable,with some exceptions. The cage is the same in the XP as it is in pretty much every Polaris AWD ATV back to 2007.

Part number 3234466
Must be part of that 1% lol

Why?

 

<div class="FTQUOTE"><begin quote>Originally posted by: HIGHOCTANE

<div class="FTQUOTE"><begin quote>Originally posted by: DODGE57HEMI



Well the 4wheel drive system obviously works but common sense would tell you otherwise that someting is just not right with this situation. I know if it were on a regular vehicle like a Jeep there would be major issues LOL!</end quote></div>



Dodge..I watched the video..I agree if the wheel speed difference were that much on pavement it woud be very bad! There is no way that is the case.

That got me thinking. I really haven't looked into the front diff operation too much. So I dug out the service manual. I'm still studying it but so far it looks like the front axles are not positivley locked to the ring gear, they are connected by clutch packs and sort of an overrunning clutch assy. The way it is designed is that when on hard pack,or pavement,or anywhere there is enough traction to keep the rear from spinning the gearing is set up to keep the front axles turning faster than the ring gear carrier. The front is geared to turn a little slower than the rear. In otherwards the front axles overrun the the carrier and turn faster than the carrier as they spin the same speed as the rear wheels, and this is what keeps it out of AWD until the rear slips. Once the rear slips the front/pinion/ring gear carrier meets axle speed and engages and locks the front alxes to the ring gear carrier mechanically. No speed sensor or anything like that is used to determine wheel slippage(as I have seen some say) If the front and rear were geared the same it would constantly be in and out of AWD,even on solid ground. So with solid traction the fronts free spin and will not bind on pavement. So you can ride around all the time in 4wd(just like the manual says you can) other than possible wear and tear on the AWD coil. Must be why the Polaris doesn't have the caution about not riding on hard surfaces in 4wd huh?

Anther plus for Polaris AWD in my book...really the credit goes to Hilliard, Polaris is just smart enough to know a great system when they see it.</end quote></div>

HIGHOCTANE, that explanation is right on the money.

 

I love the Polaris 4x4 system. My best friend rides a Grizzly 660 and there are times I just cruise through a mudhole in 4x4 and he gets stuck in it in 4x4. Then once he's stopped he has to push a button, flip a lever, and push another button to lock it in. After he finally gets through the hole he has to stop, push a button, flip a lever, and push a button to unlock it before he can go fast again and catch up to me. His engine is 1/3 bigger than mine so he can go a little faster than me but my 4x4 system is better IMO. Even in 4x4 lock he got bogged down in some mud holes I went through because his stock tires were so crappy. That even happened when I only had 25" tires too. YMMV.

 

The way you would most likely break a roller cage would be from doing donuts in 2wd with alot of tire speed and cold diff oil.The oil creates to much friction or resistance similar to too much oil pressure and causes the rollers to ramp up engaging the output hubs while the rear tires are spinning fast and the fronts are not.A plastic roller cage is used because it can crush and allow the front axles to keep turning.A steel cage would jam and lock the front tires from spinning or explode the front case.Also I think the front is geared 3.23 and the rearend is geared 3.80.

 

<div class="FTQUOTE"><begin quote>Originally posted by: HIGHOCTANE

The manual I am referring to is for the 08 700/800,but most of the front diff parts are interchangeable,with some exceptions. The cage is the same in the XP as it is in pretty much every Polaris AWD ATV back to 2007.



Part number 3234466

Must be part of that 1% lol



Why?</end quote></div>

Cool that is what I was getting at is wondering if they updated it on the XP! THANKS!

 

<div class="FTQUOTE"><begin quote>Originally posted by: jumbofrank

I love the Polaris 4x4 system. My best friend rides a Grizzly 660 and there are times I just cruise through a mudhole in 4x4 and he gets stuck in it in 4x4. Then once he's stopped he has to push a button, flip a lever, and push another button to lock it in. After he finally gets through the hole he has to stop, push a button, flip a lever, and push a button to unlock it before he can go fast again and catch up to me. His engine is 1/3 bigger than mine so he can go a little faster than me but my 4x4 system is better IMO. Even in 4x4 lock he got bogged down in some mud holes I went through because his stock tires were so crappy. That even happened when I only had 25" tires too. YMMV.</end quote></div>

Your friend doesn't have to stop to switch into diff lock, or 3WD for that matter. They suggest that you be under 15mph before switching into 3WD and under 10MPH before switching into diff lock. It is a safety thing as the engagement could affect handling.

As for advantages of diff lock, it does not require that your rear tires break traction before the 4WD works. Sure, it is only 1/5th turn but if your rear tires are hooked up solid then it can require some heavy throttle at first in order to get those rear tires to break free. Watch the XP comparison video, against the Grizz, when they test the AWD systems with the obstacle in front of the right front wheel. The extra throttle needed to break traction on the rear tires causes the XP to pop up over the obstacle more aggressively than the Grizz. Both machines make it over the obstacle with no difficulty but they are different and some riders will prefer one system over the other for this reason. Another situation is in heavy snow. If the rear tires hook up well on your Polaris then they will not spin and your AWD will not engage. Personally, I think steering is better with the diff lock when riding in snow.

They are both great systems that are very capable. One is not better than the other, they are simply different. I am thankful for the variety as I don't always want to ride my Polaris. If I could only own one, I would pick up an X2.

 

<div class="FTQUOTE"><begin quote>Originally posted by: miande

As for advantages of diff lock, it does not require that your rear tires break traction before the 4WD works. Sure, it is only 1/5th turn but if your rear tires are hooked up solid then it can require some heavy throttle at first in order to get those rear tires to break free. Watch the XP comparison video, against the Grizz, when they test the AWD systems with the obstacle in front of the right front wheel. The extra throttle needed to break traction on the rear tires causes the XP to pop up over the obstacle more aggressively than the Grizz. Both machines make it over the obstacle with no difficulty but they are different and some riders will prefer one system over the other for this reason. Another situation is in heavy snow. If the rear tires hook up well on your Polaris then they will not spin and your AWD will not engage. Personally, I think steering is better with the diff lock when riding in snow.</end quote></div>

I understand exactly what you are saying. I haven't watched the vid,but I climb over fairly large downed trees all the time. These trees are large enough that if you pull upto them in 2wd it will just try to push the tree most times. Looking at the way the system works you would think that the fronts would not pull up on to the tree without the rear spinning,but IMO they do! However much it takes (1/5 is what I keep seeing people post,but the manual makes no reference to it,I don't think that is accurate) it isn't enough to be detectable IMO. I have pulled up to downed trees and stopped with the fronts touching the tree,then just eased right over with no need to give it excess throttle and "make the rears spin". It doesn't just bulldoze the fronts against the obstacle(as it does in 2wd) until the front kicks in and all of a sudden jump over. In other situations I've crossed logs at an angle in 2wd and it would try to throw the machine ans cause it to ski down the log,hit the switch an turn into the log and it immediately goes in the direction YOU want to go.
Like I said I don't know what the guy in the video is doing,but I have tested the systems ability to cross obstacles,and it does not require excessive throttle, like you would think, to engage the front. It is very controllable. If I can get someone to video it this weekend I'll show you.