I just purchased a 2018 Zforce 1000 with 650ish original miles.  The owner stated he just had a engine replace under warranty.  I'm not sure this has any bearing on this issue or not.  But during my first trip to a local motosports park in Colorado, I noticed fluid leaking from my rear differential. I ran it around the UTV track but not too aggressively in my mind.  But it was 30 degrees out.  I'm looking for advice. First, any thoughts on what may have caused this crack in the location in the pics.  Is this a fluke or a common CF moto issue.  I didn't see much on this forum so maybe not a systemic issue.  Is there anything I should do to mitigate this from happening again once I fix it. Second, I plan on attempting the repair myself.  I'm not any experienced mechanic but can do a fair amount and I will likely solicit a couple of more experience buddies.  I purchased a CFMoto service manual.  It has some good sections and some not so good sections.  I would put the rear gear case (I call it a Differential) in the latter category.  It looks possible to replace the outer housing by just dismantling the left side axle and swapping it out as is.  Yet should I take the rear diff out completely to do a full inspection? What should I be worried about with this repair work.  With respect to inspection, is there anything other than the obvious I should pay attention to?  I'll look for metal shavings in the oil or play in the gears or obvious wear on attach points. It's kind of a bummer that I ended up with something broke on my first outing, but oh well.  That's what comes with having fun sometimes. 

[2015 Z Force 800 53/Trail EPS]

The first thing I might say is..don't blame yourself. It may have already started to have a problem before you bought it...and why was the engine replaced so soon one might ask. Secondly, yes, completely remove it and disassemble for a complete inspection. Any forces that caused the case to fail can and will most likely cause other things to happen such as stress cracks, flexing and alignment changes on other parts like the pinion. In the least a complete re-shimming may be necessary. Good luck and post pics with your progress. There will come a time soon when I myself will be pulling mine and either rebuilding or replacing it as I have something grinding the case up slowly.

Also have to ask, did the previous owner modify the suspension in any way like installing a lift kit, different a-arms, larger tires, wheel spacers..ect?   

The previous owner said the dealership's explanation was dust intrusion into the engine.  Maybe Air Filter wasn't cleaned well enough. I bought a two stage Uni filter to improve that. but the excuse seemed a little weak to me. No mods to the suspension. the shimming aspect has me worried since there's very poor description in the service manual on this aspect among other things.  The whole assembly looks fairly easy to remove though. I kind of assume that if i take it off and put it back on exactly the same I should be good with respect to shimming, but I did see a post about a person having to replace the differential several times and attributed the potential cause to poor shimming from the start.  In part, if the engine was replaced maybe the shimming aspect was not accomplished properly.  But worse case, I can maybe take it to the dealership for final install to get it aligned properly.

[2015 Z Force 800 53/Trail EPS]

The previous owner said the dealership's explanation was dust intrusion into the engine.  Maybe Air Filter wasn't cleaned well enough. I bought a two stage Uni filter to improve that. but the excuse seemed a little weak to me. No mods to the suspension. the shimming aspect has me worried since there's very poor description in the service manual on this aspect among other things.  The whole assembly looks fairly easy to remove though. I kind of assume that if i take it off and put it back on exactly the same I should be good with respect to shimming, but I did see a post about a person having to replace the differential several times and attributed the potential cause to poor shimming from the start.  In part, if the engine was replaced maybe the shimming aspect was not accomplished properly.  But worse case, I can maybe take it to the dealership for final install to get it aligned properly.

I also don't think it helps any that they use the same diffs/gear cases in both the 800s and 1000s.

Here's my update to all the repair fun I've had.  I will post pics in the next entry to help.  But for now here's the words.  As per my original post, I cracked the left side housing plate (not the main diff housing that hosts the pinion gear).  I went online to CFMOTOwarehouse.com (also named Brolin parts LLC).  The website says shipping in 6-14 days.  I ended up modifying my purchase a week later to add an oil seal which I should have known to buy in the first case.  But the rep was helpful in general and responsive to phone calls.  However, it still took a little over 3 weeks to show up.  not quite Amazon prime speed.  But oh well.  I then proceeded to get the differential out. The service manual I purchased online was less than useful in that it had little info on removal process.  It basically said remove the axle and applicable parts.  thanks...  But removing the axles were not too challenging.  It took a long breaker bar and some heat to get the axle nut off but it worked.  The process was not much different than other vehicles so Youtube helped here.  The axles popped out of the differential with a little maneuvering but not too much that I was worried about messing up the CV joints.  I did learn that if you must remove the brake calipers then be careful the break piston will close and thus later it was harder to insert the rotor back.  but that's break job 101 re-learned again. But here's where the real fun started.  there are 4 bolts on the housing.  But there are also mounting brackets that must come off too.  you can't get to all of the nuts/bolts without removing the upper suspension arms.  And then I had to remove the sway bar as well.  Oh well, just gave me an opportunity to re-grease everything. Then you need to remove the Hex bolts on the front of the diff connecting to drive shaft.  It's hard to get to these things without the perfect tools and being a contortionist.  my socket wrench was just about 1/4 too long to fit between the bolts and the opposite bolts to the engine housing. But I figured out a minor hack by using my hex socket and a ratcheting flat wrench inserted between the socket and the bolt.  OK, so now I have the differential free and ready to be removed straight out the back.  But it doesn't fit.  no matter how I turned it I couldn't get it out.  the opening space in the main frame was about 1/32 inches too small. I don't know if this was supposed to be large enough or that my frame was not toleranced the best or I just didn't turn the diff the right way.  So I ended up removing the left (cracked) housing cover (8 bolts I recall) and then removed both main pieces separately.  Don't forget to remove the old diff oil first... it was still a little messy just the same.  But now I can inspect the diff and I found that I had metal shavings from some damage to the gears.  So now I'm stuck with a dilemma.  Are they damaged enough to want to swap those out and also deal with re-shimming the whole thing.  or just put it back together and wait until the whole thing breaks again.  Rather than risk braking while 30 miles out in the desert somewhere, I decided to buy a whole new differential.  The comparison cost was roughly 350 spent on replacement parts and maybe 200 to get a local mechanic to re-shim it for me.  it's an art not a science and one local mechanic didn't have any experience.  or 900 for a totally new one.  Also note that CFMOTO changed the design. the new housings are "beefier".  it was obvious that they improved the housing design to make them stronger. I suspect because the housing were cracking like mine did under normal use.  So having a new one that might last longer pushed me over the edge.  In the process, I started talking to a local dealership who offered me a differential at the same price as I could get it online. And they said it would ship in 4-6 days.  It was the dealership in Fort Collins CO.  Kudos to them and nice folks too!!  So for the first time ever I will buy parts from a dealership (like the old days...). One thing to note about the new part and if you ever replace something on them in the future.  there's a little air port on the left side housing.  this is pressure fit and you will likely ruin it if you try to swap it.  So if you just replace the housing, you need to buy this as well.  there's also a plate inside, but these can be swapped.  Finally the new part has additional "ports" on the left side housing. one set of ports go into the boot housing.  these are not present in the 2018 part.  there is no hose or anything here so don't worry about it.  but there's another threaded port into the interior.  The replacement differential came with a bolt screwed into that. It's maybe another viewing port or oil port, but it wasn't clear.  but the replacement left housing from online didn't come with it.  That confused me when I got it and I would have needed to figure out a correct bolt to fit there.  In any case, now I was ready to put it back into the vehicle. I had to do the reverse in that I had to install the left housing after I inserted the main part of the diff into the gap in the frame.  kind of a pain but oh well.  The rest of the install had some minor challenges but mostly due to my lack of true mechanic skills and thinking through the right sequence of bolts to install.  start front to back...  Once I got it all back together, I drove it around the neighborhood to discover that another issue I was having just got worse.  It's having troubling shifting out of gear and into reverse.  So I've got to do some reading on that and I suspect I'm not going to like it.

This likely won't make you feel any better but it may help someone else.

Looks like the 1000 has an updated rear diff (Q860) from the 500 and 800 (Q530).

MortchMotor.com sells the Q530 rear diff complete for $366. I imagine shipping would be around $50 but it's DHL and usually arrives in 4 to 4 days from China.

I could not find a Q860 on the Mortch website, but aliexpress  has it for $565 - don't know about the shipping costs.

i couldn't find same reference points but now I have more problems.  before I even had a chance to post photos, I wanted to test out my new differential.  I went on the UTV track at IMI and played around for 20 minutes or so.  It had a high pitched whine that drowned out the engine noise under load. And then it mostly stopped driving the wheels.  I hear what sounds like grinding from the rear and so I stopped. I was also having problems shifting between forward and reverse.  Now I've no clue what's going on.  I took off the CVT cover to confirm the belt is in good shape- looked new.  I removed the differential oil plug to see if I somehow destroyed the gears in my diff. It was brand new so how could I have screwed that up.  but the oil and the plus didn't seem to have any metal shavings.  I raised the rear and turned the wheels to see if I could diagnose anything strange with the drive shaft or diff.  It had some play but I figured a little of play was OK.  so now i'm stuck taking it to the dealership to figure out what's wrong.  Unless someone has some suggestions for further diagnosing it.  It has to be with the gear shifting/transmission something.  I'm really thinking I got sold a lemon here.

[2015 Z Force 800 53/Trail EPS]

i couldn't find same reference points but now I have more problems.  before I even had a chance to post photos, I wanted to test out my new differential.  I went on the UTV track at IMI and played around for 20 minutes or so.  It had a high pitched whine that drowned out the engine noise under load. And then it mostly stopped driving the wheels.  I hear what sounds like grinding from the rear and so I stopped. I was also having problems shifting between forward and reverse.  Now I've no clue what's going on.  I took off the CVT cover to confirm the belt is in good shape- looked new.  I removed the differential oil plug to see if I somehow destroyed the gears in my diff. It was brand new so how could I have screwed that up.  but the oil and the plus didn't seem to have any metal shavings.  I raised the rear and turned the wheels to see if I could diagnose anything strange with the drive shaft or diff.  It had some play but I figured a little of play was OK.  so now i'm stuck taking it to the dealership to figure out what's wrong.  Unless someone has some suggestions for further diagnosing it.  It has to be with the gear shifting/transmission something.  I'm really thinking I got sold a lemon here.

There has been a good number of the idler/overriding clutchs gone bad. When it starts seizing it either applies pressure on the belt and/ or spins against the belt making a very high squealing sound and making it near impossible to shift gears because of all the pressure its putting on the transmission. If it shifts OK shut off.. but not running, look to this first. It's #17 in this image.

thanks, in the 2018 zforce CVT expanded diagram, that's just listed as a "bearing". I assume you are saying that the bearing is "seized" and causing the squeal.  that does make sense.  we assume it had something to do with the CVT.  But for the fix, I assume I should pull out the drive pulley and replace that bearing.  I watched some videos including yours (thanks!!) on how to do the removal of the pulley but nothing specific to the bearing. If I only remove the drive pulley that should be really easy since there's special tools to get the driven pully nut off/on but not so much the drive pulley.  removing/replacing the bearing may be more of a challenge if pressure fit, but I'll figure that out or get help from machine shop friend.  Once again the service manual leaves a fair amount to be desired on this repair.  the attached pic from the manual shows the drive moving pulley as one piece with what appears to be the bearing against the larger disk.  the parts list you had showed many more moving piece/parts.  and yes, i'm hoping this is a relatively easy/cheaper fix.  you can see my frustration with buying this vehicle used and immediately having multiple problems and not being able to enjoy it.  Thanks again for spending time on me (and others) with your advice and counsel.

[2015 Z Force 800 53/Trail EPS]

Yes, simple if that's what's wrong. Will have to pull it down to see if it is though. An if what's in yours is a oneway, make sure you put it in the correct direction.

Well, it appears that this isn't the problem.  I removed the cover and then removed the outer drive pulley/limit plate from the shaft.  I coerced the belt off of #17 or what's referenced as the overriding clutch in the diagram.  It's a large wide bearing and it feels like a bearing should.  rotates freely without any play or obvious physical damage or non-smooth rotation.  The pully surfaces have visible striations but they are smooth to the touch so it appears just cosmetic. The only thing I find odd is the nut for the driven pully seems to not be threaded far onto the shaft.  there's a lot of interior thread showing.  I wonder if that was installed correctly.  But I'm back to the drawing board and looking at taking it into the dealership to diagnose.  I'll clean it up a bit and put it back together. 

[2015 Z Force 800 53/Trail EPS]

Some have had an alignment problem which is a matter of spacers behind the clutches.