Locked 80 rear diff center in a hzj75 housing. (1 Viewer)

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Dec 29, 2020
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Hi guys.
so I have a 93 hzj75 and the rear diff has just s**t itself. I have an 80 series that I was breaking and still have the locked rear axle with actuator and Ecu ect that I wanting to use as finding 75 series parts in the uk is near on impossible!
I did find a post about retro fitting it into the 75 housing but I’ve been searching for hours too no avail. Does anyone have any details on this.

thanks for your help!
 
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Jun 13, 2014
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I have fitted 80 front and rear diff in my 78 , but it's not that easy .
If you want to keep the lockers working , it's also another job by itself .
Don't know if the half shaft on 75 are the same as on 78 .
Might be ???
You must mill the rear dif housing in order to mont it .
Front one much easier .
 

Indestructible 47

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Straya
I think you will find that the 80 series use a different axle shaft spline count. At least, the 79s are different. Just double check.

The housing will need to be notched, order up a factory locker gasket and trace it to get close. You will need to replace 2 studs with longer ones that go through the actuator.

You will need the locker axle shafts. They are different to non locker types.

Check the gear ratios. Make sure they match at both ends. You can get away with 1 diff a 4.11 and the other a 4.10. Same ratio really.

All in all, very expensive to do, not worth it imho unless you are doing a to factory spec build. It will be cheaper to just stick an air locker in there, and rebuild the current diff at the same time.
 
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Dec 29, 2020
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I think you will find that the 80 series use a different axle shaft spline count. At least, the 79s are different. Just double check.

The housing will need to be notched, order up a factory locker gasket and trace it to get close. You will need to replace 2 studs with longer ones that go through the actuator.

You will need the locker axle shafts. They are different to non locker types.

Check the gear ratios. Make sure they match at both ends. You can get away with 1 diff a 4.11 and the other a 4.10. Same ratio really.

All in all, very expensive to do, not worth it imho unless you are doing a to factory spec build. It will be cheaper to just stick an air locker in there, and rebuild the current diff at the same time.

I have a complete locked diff, housing and shafts out the 80 series, basically I have a whole 80 series that I can rip apart.
As for modifying the housing this isn’t a problem, it’s more the shaft lengths I’m worried about, would the 80 shaft I believe short side for the locker fit the 75 housing? I’m pretty sure they’re identical spline wise.

as for the actuator, Do I need to run the ecu or can I just hardwire it in?
thanks mate
 
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Jul 3, 2004
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Anchorage, AK
I have a complete locked diff, housing and shafts out the 80 series, basically I have a whole 80 series that I can rip apart.
As for modifying the housing this isn’t a problem, it’s more the shaft lengths I’m worried about, would the 80 shaft I believe short side for the locker fit the 75 housing? I’m pretty sure they’re identical spline wise.

as for the actuator, Do I need to run the ecu or can I just hardwire it in?
thanks mate
I don't believe the short side shaft is replaceable by any other model. the long shaft I think is same as on the 60.
 
Joined
Jun 13, 2014
Messages
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Milano - Italy
I have a complete locked diff, housing and shafts out the 80 series, basically I have a whole 80 series that I can rip apart.
As for modifying the housing this isn’t a problem, it’s more the shaft lengths I’m worried about, would the 80 shaft I believe short side for the locker fit the 75 housing? I’m pretty sure they’re identical spline wise.

as for the actuator, Do I need to run the ecu or can I just hardwire it in?
thanks mate
Actuator , you definitely need the ecu .
The half shafts of the 80 are too wide to fit in the 75 .
Can't remember how much , but approx 50-60 mm each side wider .
You will end up wit a 75 , with wheels sticking out of the frame of the car .
Doubt that you will pass DOT with those .
For this reason you need to have 75 original shafts
 
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lenexa, ks
Front should be easy. I put an unlocked 80 series diff in my 75, everything was the same.

Rear would be an issue with shaft length. how about swapping the entire axle? The 80 is a lot wider than the 70 axle, so you would need different rims with a very different offset. I think we are talking about 2" on each side. Run spacers on your front tires.

pretty sure that @Bydge put front and rear 80 series axles under his rig.

To be clear, not saying this is easy at all. A lot of time, but not much $$$ to do it this way.
 
Joined
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uk
thanks for your help guys,
So in the end I cut all the mounts off the 80 axle and welded on the 75 spring perches, was an easy job just took a lot of measuring and getting angles right but it’s in and the track is spot on, just need some arche extensions now as the tires hang out around 60mm.
will be doing the same with the front I believe, i was tempted to go down the ifs front hubs route but after hearing it puts the same amount of pressure on the bearings as wheel spacers I think the 80 route is a lot better, also parts are a lot easier to get for an 80 in the uk!
 

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