750 Sector Rear Diff Swap

[CarlB]

I have a 2022 Hisun 750 Sector which comes with a locked rear differential. Was wondering if it would be possible to install an unlocking differential.  I see that there are some Hisun made machines that come with the unlocking rear diff, such as Cub Cadet Challenger, some of the Massimos, and probably others. My concern is whether these would be a direct bolt on, using the original axles, drive shaft, and of course matching gear ratio. I've tried to match up part numbers but it seems every brand has their own number system even for parts that I know are identical. If anyone has ever done this swap or has any information about the whether these unlocking rear diffs are comparable to the Sector, I'd appreciate your input.

[that guy from Canada]

You would have to do the research on axle fitment hubs etc.

Motorcycle doctor has most the microfiche.

Unless your worried ab9ut tearing up your lawn on sharp turns unlocking diff simply has more parts to break inside... just saying

[HISUN Sector 750 EPS Failu]

Somewhat related, it appears we have to replace the rear differential on our 2020 Sector 750, with 110 hours.

Any advice you can give us and our local mechanic would be appreciated.

Thanks,

[HISUN Sector 750 EPS Failu]

Also related, is it possible to disable/disconnect the rear wheel drive, and operate in 4WD, with just the front pulling?

[Pop Bob]

Of course it is. But why would you. You mean because the front diff unlocks?

[HISUN Sector 750 EPS Failu]

On 7/21/2025 at 12:26 PM, HISUN Sector 750 EPS Failu said:

Also related, is it possible to disable/disconnect the rear wheel drive, and operate in 4WD, with just the front pulling?

I asked HISUN Tech Support exactly that, and the answer is no.

I also found out that it is probably not my rear differential that has gone bad.  It is more likely that the splines in the coupler have sheared.  It's engineered for them to fail first, in order to save the differential.

In any event, the HISUN Tech Team is going to work with our local repair facility, to walk them through diagnosing and repairing our Sector 750 EPS.  Hopefully it is just a $20 coupler.

[Pop Bob]

Yup- that would be a good thing

[HighSon]

On 7/31/2025 at 5:04 PM, HISUN Sector 750 EPS Failu said:

I asked HISUN Tech Support exactly that, and the answer is no.

I also found out that it is probably not my rear differential that has gone bad.  It is more likely that the splines in the coupler have sheared.  It's engineered for them to fail first, in order to save the differential.

In any event, the HISUN Tech Team is going to work with our local repair facility, to walk them through diagnosing and repairing our Sector 750 EPS.  Hopefully it is just a $20 coupler.

That exact failure occurred with my 750 with about 3500 km.  It's clearly a factory defect...either the splines are not hardened or they just corrode and degrade from moisture.  Really ought to be greased IMO but mine was dry as the desert from the factory.  When I replaced, I greased the parts well for assembly.

[HISUN Sector 750 EPS Failu]

34 minutes ago, HighSon said:

That exact failure occurred with my 750 with about 3500 km.  It's clearly a factory defect...either the splines are not hardened or they just corrode and degrade from moisture.  Really ought to be greased IMO but mine was dry as the desert from the factory.  When I replaced, I greased the parts well for assembly.

We are hoping it's just the splines on the coupler.  Actually, it was HISUN Tech Team guy that said that's probably what it is, that it's engineered for the coupler to fail first, in order to save the differential.

$20 plus labor rather than $800 plus more labor.

We have had splines fail of golf course equipment, like the beverage cart axle splines because it gets "engine-braked" going down hills.

[HISUN Sector 750 EPS Failu]

Also, the Tech Team guy said it's not good that we use our UTV primarily to take our dog for a ride on our paved lake road, that it should only be used off-road, because of the wet clutch.  I never would have known that!

[HighSon]

45 minutes ago, HISUN Sector 750 EPS Failu said:

Also, the Tech Team guy said it's not good that we use our UTV primarily to take our dog for a ride on our paved lake road, that it should only be used off-road, because of the wet clutch.  I never would have known that!

Hmmm...not sure I buy that assertion.  I understand that you should not drive around in high gear except when driving at higher speeds due to excess wear on the clutch, even though it seems smooth and quieter driving around in high.  FWIW, our is driven only on the street.  Original clutch still operates as new at 4500 km.

As for the spline wear being a prophylactic measure, sounds reasonable, but it seems to me that as it wears out it may put greater impact loading on the rear end gears. I noticed ours getting "lurchy" before it failed.  When you pull it apart and nothing but rust crumbs fall out it and the splines are worn to nubs makes you believe its not intended to fail that way.  In my case it was not an instantaneous failure of splines from over-stressing the drive train.  I attribute my spline failure (and I suspect some others may be as well) as a direct result of using a lower quality alloy for the shaft or not properly heat treating the splines.  I like my Hisun overall, but it does suffer from some design/manufacturing defects.  Relative to it's overall value I have found it occasionally irritating but generally acceptable.  Sorry if that sounds argumentative...really just sharing my experience with the issue.  Regardless, if there's a takeaway from this it's that it is a good idea to pull the shaft and inspect it before it fails, especially if you notice your ride getting lurchy.  It's pretty easy to get at.

 

[Pop Bob]

I don’t think I agree with the tech’s advice about off road only. The machine doesn’t know or care where you are. Now there will be added stress to the clutch on road if you make tight turns. This is because the rear wheels are fighting one another and increasing rolling resistance. However, off roading also increases rolling resistance. Compare pushing a loaded wheelbarrow on concrete vs across the lawn. Point is, just drive the machine and don’t worry about this stuff. If the clutch wears out- replace it. About the only thing I’ve found that can’t be fixed is stupidity. And as yet I haven’t detected much of that on this forum. 
Pop Bob

[HISUN Sector 750 EPS Failu]

It is not intuitive that it would be wrong for two Seniors in their 70's to take their dog for a ride on their lake road. 

[HISUN Sector 750 EPS Failu]

For some reason I do not seem to be able to find additional posts, but for the one asking if we could just disconnect the rear wheel drive, and operate off the front (in 4WD mode), Tony with the Tech Team said "No".  That may have to do with the computer stuff, that it needs to read it all connected.  He didn't say why it's a No.

We have tried operating in 4WD, to take pressure off the RWD, and the RWD issue is still there, feeling it missing a beat, and probably getting worse. 

But, with it possibly being sheared connector splines, that's less serious than replacing the rear differential.

I'm still waiting for my local repair facility to let me know that the HISUN Tech Team has reached out to them.

[HISUN Sector 750 EPS Failu]

Since it might just be the coupler, rather than  the differential, is this something I can DIY?  Disconnect the driveshaft and put on a new coupler?

[HighSon]

14 minutes ago, HISUN Sector 750 EPS Failu said:

Since it might just be the coupler, rather than  the differential, is this something I can DIY?  Disconnect the driveshaft and put on a new coupler?

Yes, but it does require that you have at least a bit of mechanical ability.  You don't have to remove the CV axles or anything, so it is pretty simple for someone who does, say, their own maintenance.  You just have to drop the splash pan under the rear end, remove the 2 or 3 differential mounting bolts, and remove the rear lower diff mount.  This will free up the rear end so you can slide it rearward enough to slide the shaft out.  There are a few different variants of the drive shaft assembly but they are all similar.  Be aware of the spring or springs that sit on the shaft (some on both ends, some on one end).  There is a bolt-on splined receiver on the diff and a splined coupler between it and the drive shaft.  On mine, the coupler and the receiver were actually what failed.  There is a good YouTube showing how to do it that you can judge for yourself if you can do it on your own.  Search for "Vector 700 itv remove rear driveshaft" and it should pop up.  Hope this helps.

[HISUN Sector 750 EPS Failu]

On 8/5/2025 at 3:47 PM, HighSon said:

Search for "Vector 700 utv remove rear driveshaft" and it should pop up.  Hope this helps.

Based on that video, I'm thinking about fixing this myself.  Swing the skid plate out of the way, remove 5 bolts, coax the differential back a ways, jiggle out the driveshaft.

 

[HISUN Sector 750 EPS Failu]

What the video doesn't show is diagnosing what has failed, and whatever you have to do to get the driveshaft back on, and the differential back in place.

[HighSon]

2 hours ago, HISUN Sector 750 EPS Failu said:

What the video doesn't show is diagnosing what has failed, and whatever you have to do to get the driveshaft back on, and the differential back in place.

A visual inspection is all that’s required to determine if any of the parts has failed. If any of the splines are worn off or damaged, that’s the problem. Assembly is just swapping out the shaft, bushing and/or receiver, putting the shaft components back together, and putting everything in place in back in reverse.  As a mechanic, I view it to be a very simple procedure.  But if you don’t feel confident after watching the video, it may not be something to attempt.

Here is a photo of the shaft assembly from my 2022 750 Sector, which may differ slightly from others.  The star shaped part on the right unbolts from the parking brake disc IIRC.

I also recommend you examine the parts exploded diagram for your vehicle.  Motorcycle Doctor has just about all of them on their site and they’re also an excellent source for parts and technical info. 

 

 

[HISUN Sector 750 EPS Failu]

On the phone, "Tony" with the Tech Team said that the coupler is designed to use only 1/2 the splines, so if that's what has failed, you can just reverse it and use it.  I would have to look at everything to  make that judgement, since it's only a $20 item.  It depends on what splines are worn.

When I'm considering DIYing it, I'm thinking that would not be any more work than renting a trailer, loading it, hauling it to the repair facility, then doing that again when it's fixed.  When I bought it, and went to pick it up, I learned the hard way that the "correct" size UHaul trailer does not work because they have a raised back.  I had to return it and exchange it for a car hauler trailer, and that made a short day way-too-long.  I have a "Carry On" trailer with a rear ramp I figured would work, and it doesn't either.

 

[HISUN Sector 750 EPS Failu]

3 hours ago, HighSon said:

The star shaped part on the right unbolts from the parking brake disc IIRC.

 

 

 

Why did you take that off?  Was it damaged?  The video did not show it, just jiggling the driveshaft loose.

[HighSon]

Because the splined bushing (coupler)on mine had damaged the internal splines of the rear receiver (a.k.a, "sole plate") from banging back and forth.  It's not necessary to remove to get the drive shaft out; but you should inspect it, and if the splines look bad, you should consider replacing. That video I referenced was simply how to remove the drive shaft.  You still need to diagnose and repair.  Inspect all the parts closely.  slide each of the splined sections in and see how much lash they have.  If it's excessive on any of the components, replace. Or as noted above, possibly invert the coupler...but for my money and time, I would replace.

[HISUN Sector 750 EPS Failu]

6 minutes ago, HighSon said:

Because the splined bushing (coupler)on mine had damaged the internal splines of the rear receiver (a.k.a, "sole plate") from banging back and forth.  It's not necessary to remove to get the drive shaft out; but you should inspect it, and if the splines look bad, you should consider replacing. That video I referenced was simply how to remove the drive shaft.  You still need to diagnose and repair.  Inspect all the parts closely.  slide each of the splined sections in and see how much lash they have.  If it's excessive on any of the components, replace. Or as noted above, possibly invert the coupler...but for my money and time, I would replace.

Exactly what I was thinking, and the way mine has been "knocking", I know it's tearing up more splines.

[HISUN Sector 750 EPS Failu]

Should it be on jack stands?

[HighSon]

16 minutes ago, HISUN Sector 750 EPS Failu said:

Should it be on jack stands?

It's easier but not required.

[HISUN Sector 750 EPS Failu]

Then I'll use jack stands.  I'm 99% ready to do this.

[HISUN Sector 750 EPS Failu]

Any tips on getting it back together.  I'm guessing it will take a bit of coaxing.

What do you think caused your spline damage?  We do not operate ours hard at all.

[HighSon]

1 hour ago, HISUN Sector 750 EPS Failu said:

Any tips on getting it back together.  I'm guessing it will take a bit of coaxing.

What do you think caused your spline damage?  We do not operate ours hard at all.

Not really.  Just make sure you lift the rear end to align as you slide the assemblies back together.  It sags without the mounts.  Which reminds me, before you unfasten the rear end, make sure the speed sensor at the rear of the diff (brass fitting with black cable coming out) has some free slack.  You don't want to damage the cable if it becomes taut when the diff is loosened.  If the sensor cable is zip tied to the frame, clip the zip tie first.  Then unplug the sensor.  This will give you all the slack you need.

My spline damage appeared to be caused by heavy corrosion of the parts, weakening the wear surfaces.  Had it been assembled from the factory with grease, I doubt it would have failed so quickly. I reassembled all the new parts with grease.

[HISUN Sector 750 EPS Failu]

2 hours ago, HighSon said:

Not really.  Just make sure you lift the rear end to align as you slide the assemblies back together.  It sags without the mounts.  Which reminds me, before you unfasten the rear end, make sure the speed sensor at the rear of the diff (brass fitting with black cable coming out) has some free slack.  You don't want to damage the cable if it becomes taut when the diff is loosened.  If the sensor cable is zip tied to the frame, clip the zip tie first.  Then unplug the sensor.  This will give you all the slack you need.

My spline damage appeared to be caused by heavy corrosion of the parts, weakening the wear surfaces.  Had it been assembled from the factory with grease, I doubt it would have failed so quickly. I reassembled all the new parts with grease.

All good to know.

 

Thanks.

[HISUN Sector 750 EPS Failu]

On 8/9/2025 at 1:43 PM, HighSon said:

Because the splined bushing (coupler)on mine had damaged the internal splines of the rear receiver (a.k.a, "sole plate") from banging back and forth.  It's not necessary to remove to get the drive shaft out; but you should inspect it, and if the splines look bad, you should consider replacing. That video I referenced was simply how to remove the drive shaft.  You still need to diagnose and repair.  Inspect all the parts closely.  slide each of the splined sections in and see how much lash they have.  If it's excessive on any of the components, replace. Or as noted above, possibly invert the coupler...but for my money and time, I would replace.

I just noticed in the video that he did not remove the "sole plate".  You did.  Since yours was damaged, and I need to inspect mine, I probably need to remove it, too.  If I do that, I'm guessing I will not need to "jiggle" the drive shaft loose (because it will be in the "sole plat", or have much of a problem getting in back connected, for the same reason

Does that make sense?

Wouldn't greasing the splines make them more likely to slip?