Polaris RZR Forum - RZR Forums.net banner
1 - 20 of 35 Posts

·
Premium Member
Joined
·
456 Posts
Discussion Starter · #1 ·
Just thought I would throw this out there for the guys who may have similar issues and need a little guidance.

SYMPTOMS - My AWD would engage in 2wd just about instantly if you nailed it in 2wd and spun the tires. About rip the wheel out of your hand if you were turned any at all. I ran in AWD all the time until I could diagnose and repair the issue. AWD worked perfectly.

DIAGNOSIS - Set the rzr on 4 jack stands, rear tires on but front tires removed I began experimenting. What I noticed is the driver side axle cup seemed to bounce a little as I accelerated around 20mph in 2wd. This is when the front drive would pop in and out of AWD a few times until full locking into AWD all the while I am still running 20mph in 2wd.

So I picked up on the axle bar while accelerating to 20mph again (be careful) and 2wd worked flawless. As soon as I sagged the axle or pushed down just a little it would bang into AWD. Dead giveaway what the problem was (My buddy Kevin is the one who told me what to check over the phone, I can't take credit!).

TEAR DOWN - Upon tear down, the diff was clean. We do a lot of mud riding, so the oil had been a little milky twice but changed regularly. My armature had slight wear, starting to groove so I swapped it with another one. Might as well change it while your in there, cheap part.

PROBLEM - The problem is there is a bushing between the 2 hubs inside the front diff. This keeps the hubs aligned inside the cage. If you look at the drawing, both hubs are supported on the outer edges by bearings but locked together in the middle with a bushing to keep them in a straight line. The bushing is a press fit in one side but just snug in the other (maybe 1-2 thousandths difference new). which allows your front tires to spin interdependently of each other instead of being locked together. What happens, is over time the bushing and hub begin to wear. Mine had worn to the point it was deflecting and hitting against the rollers inside the cage and bumping it into engagement.

pictures.

Hubs together as if they were installed in the diff.



bushing between the 2 hubs





What happens over time is the wear causes the hubs to deflect and the center where they mean begins to bump against the rollers knocking it into AWD.

Image below is normal. Very little difference between the 2 hubs. This is on a 2011 800 S diff with around 200 miles on it. The deflection becomes very exaggerated over time.





I don't have the pics of mine, I took pics and did the write up after I finished it all using another diff sitting on my work bench.

SOLUTION - I had a machine shop make me a new bushing for my hubs. FYI, only 1 hub and 1 side of the bushing wear because 1 side is pressed in. As the hub wears, it tapers slightly. If the taper is too much, you may need to have them re surface it. Doesn't matter how much they bore it out as you are making new bushing. My hub had very little taper but was worn roughly .003 so my new bushing is stepped. It is a press fit in the passenger side hub and a really snug fit in the driver side so the 2 wheels can still spin interdependently.





I know there is a lot going on in this post, hope it makes sense and helps someone else out. My cost was $75 for machining, wayyyy cheaper than buying the hub assemblies or a new/used diff (very few used 900 diffs around right now too).


After all, worse things can happen!! Here's a pic of another diff's hub that shattered at the female axle splines.

 

·
Registered
Joined
·
1,246 Posts
Russel...Kudos to you for finding the cause of this problem and posting such an informative description and detailed solution. Should be in a sticky somewhere IMO.

Thanks for the effort!
 

·
Registered
Joined
·
106 Posts
One step to do before going this far is to change the diff fluid. I found on mine with really dirty diff fluid, the awd would sometimes try to kick in while driving in 2wd. Fluid change, problem gone.
 

·
Premium Member
Joined
·
456 Posts
Discussion Starter · #9 ·
I wanna say it was heat treated 4140 scrap he had laying there. But I don't remember for sure.

Much harder material than the stock bushing.

Doesn't matter if the bushing or the hub wears more here on out, plenty of room in the hub to cut a few thousandths and up the bushing size if it needs fixed again later on. I'm sure the axle splines will fail first from the mud and water.

No worry of friction welding the 2 together either. You will never spin each wheel independently long enough to build heat in the oil bath.

All good! Next big ride is next weekend, ill report back.
 

·
Registered
Joined
·
122 Posts
HOLLY CRAP! This may be the gayest thing I have ever said in my life but I could hug you tighter than spandex on 500 lb women! I have looked for days even weeks on this problem! It's EXACTLY as you describe!!!! It's EXACT! I have taken my diff apart and looked and looked and turned everything over in this diff and couldn't find the problem! I will say a GREAT THANKS TO HIGHOCTANE! He pointed me in your direction!
 

·
Registered
Joined
·
179 Posts
I have almost this same issue... Gonna have to pull the whole thing apart again.....ugh... Already had it apart 4-5 times with no luck in fixing it... Thought I was gonna have to live with AWD all the Time.... Really hope I can get it this time! Thanks for the write up! This forum is always has a wealth of knowledge...
 

·
Registered
Joined
·
179 Posts
If the bushing is pressed in on one side how did you get it out without beating the hell out of it? Got mine down to this point on the workbench and that bushing seems to have welded itself to the outer bearing part....?..? Any help would be awesome!
 

·
Registered
Joined
·
7,294 Posts
It might just be a bit of an interference fit. Not sure,

But I've had good success getting things like this apart by:

Put the whole thing in a plastic bag, Ziploc?

Put it in the freezer over night...this will shrink the whole thing.

Then put the assembly in a vise, with rubber or copper faces, using the vise to hold the inner bushing.

Then use a torch, small propane is fine, and begin warming the outer hub. Don't get carried away, just wanting to warm the hub and get it to start expanding while the inner bushing stays very cold.

Keep warming until the hub starts to expand and is should come off fairly easily.

JMO

Pirate
 

·
Registered
Joined
·
681 Posts
Interesting. My 800 is long gone but had the same symptoms once in a while. It was like the steering wheel was getting ripped out of your hands. Hard yank one way, then the other a few times, then it would go away. At first I thought it was a problem with the brakes locking up and never did get it figured out. Thanks for posting!
 

·
Registered
Joined
·
179 Posts
It might just be a bit of an interference fit. Not sure,

But I've had good success getting things like this apart by:

Put the whole thing in a plastic bag, Ziploc?

Put it in the freezer over night...this will shrink the whole thing.

Then put the assembly in a vise, with rubber or copper faces, using the vise to hold the inner bushing.

Then use a torch, small propane is fine, and begin warming the outer hub. Don't get carried away, just wanting to warm the hub and get it to start expanding while the inner bushing stays very cold.

Keep warming until the hub starts to expand and is should come off fairly easily.

JMO

Pirate
Thanks for the tip! In the Freezer! Now for the hard part.... any one got a pinion gear or know where to find a good used one!?! mine is cracked on two teeth and has a chunk missing out of another and my local polaris dealer wants like $490 for it... trying to keep money from flying out of my wallet (which is really hard with this damn toy!)
 

·
Registered
Joined
·
7,294 Posts
I'd sure inspect the sealing surface on the axle. If there is a scratch or rough spot where the seal rides...that's probably your problem.

surface the seal rides on must be very smooth

Pirate
 

·
Registered
Joined
·
122 Posts
What tolerance did you go with on the snug fitting side? 1 thousands or 2 thousands? I have a local machine shop thats going to machine the part but he said 1 thousands can mean a hole new thing compared to 2 thousands so he wanted me to check with you on the tolerance before he starts the build
 

·
Premium Member
Joined
·
456 Posts
Discussion Starter · #20 ·
Not sure, needs to be tight. almost tight enough that you can't twist it by hand when you pop them together and you have to tap them to separate.

Lube the surface that spins, although the tolerance will wipe most off.

Good luck!
 
1 - 20 of 35 Posts
Top