750 Sector Rear Diff Swap

[HISUN Sector 750 EPS Failu]

4 minutes ago, HISUN Sector 750 EPS Failu said:

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

Never mind.  AI had an answer:  "Yes, driveshaft splines should be lubricated. Proper lubrication prevents corrosion and allows the shaft to slide smoothly, which is important for proper function and to avoid issues like "clunking" when shifting or accelerating. A light coating of a suitable grease, like constant velocity grease or a grease with NGLI 2 certification, is recommended. "

[HighSon]

You are overthinking this.  Do not remove the sole plate UNLESS after you remove the shaft and coupler, you see obvious damage to the coupler.  If the coupler looks bad where it mates with the sole plate, then use a light to look into the splines of the sole plate.  If it looks damaged, then remove it at that point.  Removing that is not covered in the video because it's a different set of steps, and IIRC, you need to remove the center brake caliper in order to remove the plate and disc.  I'm not certain, but pretty sure.  It's been a while.

To your other question, it will make it easier to SLIDE, not SLIP. So no.  It's a spring loaded spline fit. It moves in and out.  It needs grease.  Moreover, it needs moisture protection to inhibit corrosion. Anyone else on this forum is welcome to a different opinion, but it won't be because it causes the splines to slip.

[HISUN Sector 750 EPS Failu]

22 hours ago, HighSon said:

You are overthinking this.  Do not remove the sole plate UNLESS after you remove the shaft and coupler, you see obvious damage to the coupler.  If the coupler looks bad where it mates with the sole plate, then use a light to look into the splines of the sole plate.  If it looks damaged, then remove it at that point.  Removing that is not covered in the video because it's a different set of steps, and IIRC, you need to remove the center brake caliper in order to remove the plate and disc.  I'm not certain, but pretty sure.  It's been a while.

To your other question, it will make it easier to SLIDE, not SLIP. So no.  It's a spring loaded spline fit. It moves in and out.  It needs grease.  Moreover, it needs moisture protection to inhibit corrosion. Anyone else on this forum is welcome to a different opinion, but it won't be because it causes the splines to slip.

Actually, that's exactly what I had in mind, to not remove the "rear drive shaft connecting seat" unless I have to.

HISUN has provided me an exploded parts view, and instructions, including that if I don't find any spline to "inspect the differential assembly".  Big Hog is in my work bay, waiting for me to finish a boat dock project.

[HISUN Sector 750 EPS Failu]

If you hear me cussing, I'm working on it!

[HISUN Sector 750 EPS Failu]

Figured out how the speed sensor plug disconnects.

You never know until you try.  The little things can be an booger.  Those two bolts holding the differential bracket are seized.  I've put Liquid Wench on them, and being patient.  I don't want to wreck the heads.

Do you think it would be possible to be able to move the differential backwards by just removing the bolt that hold the differential to it?

 I'm not sure the mounting bolts are the same as in the video, which is for a Vector, but the parts diagram for the Sector 750 does not show mounting bolts.

I have always found it strange that when I search HISUN it does not show a Sector 750 for 2020, yet ours is.

From the parts catalog:  Sector750 2016-18

Edited August 13, 2025 by HISUN Sector 750 EPS Failu

[HISUN Sector 750 EPS Failu]

2 hours ago, HISUN Sector 750 EPS Failu said:

If you hear me cussing, I'm working on it!

I guess I did something wrong, but I don't know what.

I'm on Hold, with seized bolts and questions about rear differential mounting bolts.

[HISUN Sector 750 EPS Failu]

I had tried to say, "You never know until you try.  The little things can be an booger.  Those two bolts holding the differential bracket are seized.  I've put Liquid Wench on them, and being patient.  I don't want to wreck the heads."

I got my impact on them, and they are out.

I've moved on to the next bolt, the one on the differential bracket, and it is seized, too.  I can't get Liquid Wrench or an impact on it.  Since the differential plate is now loose, does that one have to be removed, too?

[HighSon]

Unclear which seized bolt you are referring to, but if the diff is otherwise loose from the frame, you can try working it rearward. But I believe the rear lower bracket may well be in the way if it cannot be removed. 

[HISUN Sector 750 EPS Failu]

44 minutes ago, HighSon said:

Unclear which seized bolt you are referring to, but if the diff is otherwise loose from the frame, you can try working it rearward. But I believe the rear lower bracket may well be in the way if it cannot be removed. 

I got the two 10 MM bolts holding the lower bracket loose, because I could get my impact on it.  I have not been able to budge any of the other three needed to loosen the differential.  I can't get the impact on them.

It's not like the guy in the video, who did them all with a ratchet.

Just to say it, everything I've had to mess with on this new-to-me 2020 HISUN Sector 750 has been over-torqued.  I found that out on lug nuts, when I had to buy a more powerful impact wrench to get them loose.  I don't know if that is factory, or dealer, or the first owner.

So, I'm on Pause again, hoping for divine intervention.

[HISUN Sector 750 EPS Failu]

It's not as easy as the YouTube video, but I got the differential moved back and level enough that the drive shaft fell right out.

The coupler splines that go inside the connector seat are toast.  The drive shaft splines are fine.

Tony with HISUN suggested I roll the rig back and forth, and listen to the differential, to make sure it's OK.

Update:  Actually, I reversed the coupler, and it's grabbing solid in the connector plate.  That side of the coupler still has defined spline ridges, whereas on the bad side the ridges are worn off.

So I'm thinking the connector plate is OK, but I would hate to go to this much trouble again if I'm wrong.

I'm ordering a coupler today.

[HISUN Sector 750 EPS Failu]

Then I will need a YouTube video that shows how to get it lined up to get it back together.

[HISUN Sector 750 EPS Failu]

I see I have unfinished business here.  The $20 "coupler" arrived and I have everything back together, and running fine.

As I assumed would be the case, when it was time to put the driveshaft back in, the rear differential assembly was "out of whack".  I pushed the UTV forward slightly until that assembly rotated forward and down, in better alignment, chocked the wheels, worked the driveshaft in front and back, then pushed the assembly forward until the three bolt holes were almost perfectly aligned.  Easy does it, so as to not strip out threads.

Since we do not operate it faster than 20 MPH, we are just going to run it in low, the same as the Axis 500 I have at work.

It was nice to be able to DIY it because there are so few dealers.  I had set it up to be repaired in one of my garage bays, and just walked away from it when things got too much.

[HISUN Sector 750 EPS Failu]

I thought I had my own thread when the driveshaft coupler failed a year ago, but I guess not.

It has failed again.  Only 142.5 hours.  Two old people operating at 20 MPH.

That's pretty sad.

I've reached out to the folks at HISUN again, to see if they are still there.

 

 

 

[HISUN Sector 750 EPS Failu]

On 7/31/2025 at 6:04 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 was a year ago and I turned out to be the local repair facility.  It was a booger to replace the $20 driveshaft coupler.

It has failed again.  Just 142.5 hours, and we are 70-year-olds, not driving over 20 MPH.

I've reached out to the HISUN Tech Team again.  The first time around they knew it was going to be the coupler, since it is successfully engineered to fail first, before the differential.

Annual driveshaft repair, twice every 100 hours, was not in any of the advertising brochures!

[HISUN Sector 750 EPS Failu]

Sometimes it is a long route to get to where you need to get to.

The current Tech Team asked me to send a picture of the current coupler AND BOOT.  Hmmmmm!  Let me go look,  Yup, no boot, the dust cover for the coupler.  It never had a boot, from the factory.  Here's a picture of it when I took it off a year ago.  NO BOOT.  A year ago I replace the coupler and put the driveshaft back on exactly the way it came off.

[HISUN Sector 750 EPS Failu]

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Edited May 2 by HISUN Sector 750 EPS Failu
brain fart