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Discussion Starter #1 (Edited)
If you’ve been around the AWD system Polaris claims is “On The Fly” long enough or been a part of any number of Polaris forums, by now I’m sure you’ve heard of the dreadful “Exploding Front Diff”.
There is much debate on this subject about what causes it and what you can do to avoid it.
I have a theory, this theory is derived from all experiences of those I’ve read about as well as my own personal experiences.
First I’ll tell you the three categories I think most occurrences fall into:
1. Switching the machine into AWD “On The Fly” while rear tires are spinning at a rate the front diff cannot handle.
2. Running the machine in AWD, riding in a state where the AWD system is currently not engaged but then the operator mashes the throttle causing the rear tires to spin at a rate that the front diff cannot handle. If the throttle is smashed to harsh the computer doesn’t recognize the spin soon enough and before it can engage, the machine is already at 3k rpm (plus) and the rest is history.
3. Some are breaking in 2WD without the operator ever touching the AWD system at all. In this case, one would conclude that the front diff had to engage on its own somehow.

Ok, from everything I’ve read, everyone seems to think the diff cover is what is failing causing the internals to let go, while this may be the case, I’m not 100% sold on the fact that it Is where the problem begins or ends.
But before we jump into that let’s first address how the AWD system could engage on its own without switching into AWD mode.
Last year I took my quad in for what I thought was a regular service only to find out I had front diff issues. My diff cover was in tact, but the machine (while all four corners were on jack stands) was intermittently engaging AWD while the switch was in 2WD mode. The dealer then unplugged the diff, cutting any information it could be receiving from the ecu and AWD was still engaging. Impossible right, not so... In my case, there was a part that was broken inside the diff, they told me it was a magnet of sort. Not knowing exactly what is inside a front diff, I thought, ok...sounds weird, but ok. Now, this would explain 2 things; 1. The diff engaging at any given time because the magnet is broken allowing AWD to engage whether plugged in or not and 2. Now the machine may as well be in AWD all the time as it is acting as such anyway which brings me to my theory:
The front diff cover isn’t breaking first causing the internals to fail, it’s the exact opposite.
- In scenario #1 at the top, this to me is common sense, “OTF” AWD on an ATV is flat out stupid. You are asking for problems. If the internals were forged, that’d be one thing, but I think what we’d find if we had “black boxes” on these ATVs is that in the cases where the diff blows while switching on the fly, the rear wheels are spinning at a rate and the rpms are at a rate that the internals just cannot hold up.
- In scenario #2 at the top, although in AWD already, I don’t believe our ECUs are sending the information fast enough. When the operator smashes the throttle very quickly or if in snow or on ice the wheels spin so quickly that by the time the diff gets the info there’s too much momentum built up for the diff to handle the torque.
- In scenario #3, per my experience, I think there is a pre-existing condition inside the diff where it isn’t functioning properly allowing the diff to engage at any given time and the first 2 scenarios then come into play.
ANY WAY YOU SLICE IT, IT HAS TO DO WITH 2 THINGS:
1. The internals aren’t strong enough to handle the torque placed on them in the first 2 scenarios, and...
2. The technology/ecu programming all the way around is in its infancy and just isn’t quite dialed in yet.

A lot of these stories take place while riding in the snow. In snow you’re vulnerable to quick slips and spiking rpms. The ecu programming just isn’t quite there yet.
Once the internals are compromised the diff cover has no alternative but to give way. I think the updated covers keep the internals in tact, but I don’t think they’re solving our problems entirely, momentarily yes, but I’d be willing to bet eventually the internals break without destroying the updated cover.

This isn’t a testimony of facts, it is simply my take on what I think is happening.
For now, as far as I can tell, the only form of protection we have is the diff cover and never switching to AWD “OTF”. When you are in AWD, treat it as though you’re in AWD. Take it easy and hope for the best every time you ride.
 

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Which is why the 2018 XP1000s have a "new and stronger" Pinion Cover AND Bearings AND Differential Gear Case.

Whatever they have been using, it clearly isn't strong enough to take the front diff engaging whenever it feels like it.
 

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It's got nothing to do with the computer. The engagement of the front is ALL mechanical. The ONLY thing the switch does is energize a magnet that ALLOWS the Hilliard to engage when the rotational speed of the rear wheels exceeds the speed of the front wheels (ie. loss of traction). You can run down the road at ANY speed and flip the switch to your hearts content and it does NOTHING except turn the magnet on and off.
 

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Discussion Starter #5 (Edited)
Nice take! Completely wrong - but nice attempt !
Thanks BD. The forum members appreciate your wealth of knowledge and all you bring to the group.
“Completely wrong”, I don’t think. Partially incorrect in one area, maybe after reading what seems to be a knowledgeable member below has stated.
It's got nothing to do with the computer. The engagement of the front is ALL mechanical. The ONLY thing the switch does is energize a magnet that ALLOWS the Hilliard to engage when the rotational speed of the rear wheels exceeds the speed of the front wheels (ie. loss of traction). You can run down the road at ANY speed and flip the switch to your hearts content and it does NOTHING except turn the magnet on and off.
This is great information that helps me better understand the system. As I stated, don’t take this as fact, just what I’ve gathered and come to conclude on my own. Sometimes things are easier understood in simplistic terminology.
You state that the system is Mechanical yet you then state it’s engagement is driven by a magnet that is energized by a switch, does that not mean it is not fully Mechanical. So I understand that the system isn’t receiving direction from the ecu, but now that I think we can agree the system is not fully Mechanical, would you not agree that there could be some delay in the magnet creating that engagement?
The diff is breaking due to poor quality parts and the amount of torque being placed on them. The only reason this could be is that the engagement is placing too much stress on those parts. To place more stress than the manufacturer designed the parts to withstand, could it be that the magnet is creating an engagement that is too abrupt following a delay rather than more of a clutch style engagement where some slipping could be beneficial?
Also the debate isn’t over traveling down the road where all 4 wheels are traveling at the same rotational speed. The argument is when you switch over to AWD when the rear wheels are traveling faster than the front.
 

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It's got nothing to do with the computer. The engagement of the front is ALL mechanical. The ONLY thing the switch does is energize a magnet that ALLOWS the Hilliard to engage when the rotational speed of the rear wheels exceeds the speed of the front wheels (ie. loss of traction). You can run down the road at ANY speed and flip the switch to your hearts content and it does NOTHING except turn the magnet on and off.
Nice take! Completely wrong - but nice attempt !
WELL, ARE YOU GUYS GOING TO POST YOUR THEORY ? :)
It can't just be flawed pinion covers.
 

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It's got nothing to do with the computer. The engagement of the front is ALL mechanical. The ONLY thing the switch does is energize a magnet that ALLOWS the Hilliard to engage when the rotational speed of the rear wheels exceeds the speed of the front wheels (ie. loss of traction). You can run down the road at ANY speed and flip the switch to your hearts content and it does NOTHING except turn the magnet on and off.

#1 I don't think the cover is the issue. It's just the weakest link.

#2 there is an issue where these are engaging when they shouldn't. Either mechanical or electrical

#3 the knowledge is out there for the ability for these things to live via ecu protection.
 

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I agree with Polman - it is purely mechanical and probably the design looked good on paper, but in the field is proving not to be heavy enough for the abuse owners are subjecting it to. The "electrical" part is a small electromagnet that draws a plate to it and the plate then resists rotating with the Hilliard clutch causing the clutch to "lock" and transmit power to the wheels. If the rear wheel are turning faster than the front, then the front wheels pull also. There is no computer determining if and when the front drive needs to engage. If the rear brake is locked and the engine is at idle, the front wheels over drive the Hilliard and the front wheels free wheel while the magnet remains engaged - as soon as the rear wheels turn faster than the front, then the front begins to drive again. However, if the rear wheels are spinning and the vehicle is not moving, engaging the AWD could cause the Hilliard to lock suddenly generating forces greater than the housing was designed for. On The Fly means the vehicle is moving - being stuck with the wheels spinning is not OTF, that is at a stand still. In that case, get off the gas, apply the brake, engage the AWD and accelerate.
 

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I agree...mechanical with a little magnet to activate the mechanics.

The question is, if completely disconnected, why is it still engaging while on stands?

Furthermore, why did this start in 2013 after 4 years of it seemingly working fine? A move to cheaper materials by Polaris?
 

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Where to start? Weak covers are not causing diff failures. Weak diffs are causing cover failures. Got that straight? Lets move on. The engagement of AWD is purely mechanical. Read up on how a Hilliard works. The gearing in the front and rear diffs are different. When the rear wheels slip the front diff will engage. The ECU only sends an on/off signal to the diff. If the AWD switch is on it will send a signal (12v) except: When in reverse, or when the speed is above a certain MPH. The override button will counter act the previous condition.
 

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It's good to see that most Polaris owners know and understand how the AWD system actually works. Purely mechanical once the magnets are energized by flipping the switch. As to the "why" some are malfunctioning, that is a question Polaris engineers need to find the answer to. It's almost as if enough electrical charge is being generated internally to activate the magnets when there is a lot of wheel spin. Kind of like a static charge, or shock.
 
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Bob...why is this not an issue on the 570 series?
I don't have an answer to that.

It's weird, because according to some members here, (ahem..., big bore owners) the 570 is built with cheaper, inferior parts. :lmao: :fechten2:
 

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Bob...why is this not an issue on the 570 series?
I don't have an answer to that.

It's weird, because according to some members here, (ahem..., big bore owners) the 570 is built with cheaper, inferior parts. :lmao: :fechten2:
They are I proved that. It's a price point bike vs the premium xp.

Even if they have the same front. I believe the 570 doesn't have the power to break them compared to the 850/ 1000
 

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Bob...why is this not an issue on the 570 series?
I don't have an answer to that.

It's weird, because according to some members here, (ahem..., big bore owners) the 570 is built with cheaper, inferior parts. :lmao: :fechten2:
They are I proved that. It's a price point bike vs the premium xp.

Even if they have the same front. I believe the 570 doesn't have the power to break them compared to the 850/ 1000
LOL, nice try.
 
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