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Official Armchair Racer
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Discussion Starter #1 (Edited)
Like any normal person this winter I decided to install aluminum differential mounts into my aluminum 1.6 vlsd housing. Well that worked out well and fine until.. D'oh.



Faced with a couple options I quickly realized now was a perfect opportunity to not be a cheap bastard and finally do a 1.8 rear swap.

Yay! 1.8 Torsen, axels and driveshaft. Scooped up a rollbar for another build as part of a package purchase. Anyways the goods:


Now the dilemma I faced. The new T1 Torsen I scooped up obviously had the 4.1 final drive found in 94-97 cars and I wasn't about to make my already anemic 1.6 feel all the more anemic nor was I going to wait around/pay the hefty price for a NB 4.3 rear. That led me to one conclusion purchase a Kia Sportage front differential and salvage the 7" ring and pinion gearing out (4.778 for U.S.) markets. With this goal I now realized this was not going to be a plug n play afternoon in the garage swapping diffs..

A quick call around to some local breakers sourced me a low mileage Sportage front diff from a 1999 for $100 delivered. :slayer:

Fella should like so.
It looks awkward and almost like a boat engine. A table vice is very handy to have.

There are a number of 13mm and 15mm (iirc) holding the housing together. These can easily be removed without an impact wrench.
Split the housing apart with a hammer and flat head. This is what you will find.


Insert the nose back into the vice and remove this 26mm nut. You will likely need an impact gun for this part.

Remove the 4 visible bolts you see here.


These two caps should pop loose with a few gentle blows by a rubber mallet. Remove the differential/larger gear.

Use a punch and hammer to shoot the pinion lodged in the nose out the open end.

Separate the larger gear from the differential. Impact wrench needed here.

Bolts removed.

Voila. Left over bits.

And the goods..


To figure out your drive ratio count the number of teeth on the large gear and divide by the teeth on the pinion. This is a 4.778 Kia Sportage ring and pinion.

Additional reading and how to:
http://www.turbomagazine.com/tech/0804_turp_kia_sportage_s2000_garage_tech/viewall.html
 

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Official Armchair Racer
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Discussion Starter #2
1.8 Torsen tear down.
The tell tale sign that you have a 1.8 Torsen. You can see through! You'll notice a few teeth from the worm gears chillin in there as well.


Pop the case open. My diff started life as an open but here we can clearly see the Torsen installed. (small gears to right of ring gear). P/O used some sort of graphite additive along with his Mobil 1 fluids. Seems to have kept everything well lubed but sure made a mess when draining.

Zip the cap bolts off to free the differential and 4.10 ring gear.

Here you can see the pinion peaking through and the nasty graphite lube I cleaned out.



Pop the top bolts off with your air gun. 12's iirc. They are loctited in. I set these in some brake cleaner and then cleaned the threads.
After the bolts are off use a rubber or plastic mallet to tap the old 4.10 gear off the differential.

Stick the differential nose in your table vice. I padded the sides and didn't tighten to much to avoid any unnecessary damage. Get your air gun again and a 26mm to pop this nut off holding the pinion.



Took some time to clean out the alum pumpkin real well.

Torsen chilling. Awaits new Kia ring gear.

This part is very tricky. Lining up the bolt holes and pressing down the new ring gear onto the differential. Took quite some time.

Cleaned up bolts.

Cleaned the threads out and let some brake cleaner sit in the holes for a bit. Used some blue thread lock and torqued the bolts to 56 ft lbs.

Plop everything back in. The caps do need to go back on their original side or else it will be impossible to set the preload/backlash. (This is a process I didn't do and can't provide insight on. Eddie and Ian at AR made the adjustments and tuning.)



Use a press to push the Miata 1.8 pinion bearings onto the Kia pinion.
 

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Discussion Starter #3
Could it be?? Yes, yes they are in! Somehow, someway, the Autokonexion solid aluminum mounts have successfully been seated in the new 1.8 housing. Terrifying experience. Sanding, polishing, freezing, torching and all sorts of hoops to jump through to safely get these guys inside. So excited!!



Took 4 tries to fit this one. Finally tapered the leading edge because it kept digging in and going sideways. Scary business but finally got it seated straight and everything else went smoothly.




Things to consider replacing while you're in there:
Trans output seal
Differential Crush Sleeve
Differential stubshaft seals
30mm Axel nuts
If going from a 1.6 to 1.8 you will need 1.8 driveshaft bolts
 

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Nice write up. Nice and cheap alternative to buying the expensive NB diff -.-
 

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Great DIY! Love the pics! Got any other threads on building stuff like this thread? I'd like to see them.
and how much rpm @40 & 60mph?

I've done some calculations on gear reduction...if I remember, for every bump in ratio ie:4.1->4.3 there's a ~160rpm diff @60mph. So...stock [email protected] is 3,1xx rpm, yours should be around 3400.
 

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Discussion Starter #7
4.77:1 must be pretty short, do you drive any highway miles in this car?
Just driving to events. It sucks but thankfully that's all I use it for.

Great DIY! Love the pics! Got any other threads on building stuff like this thread? I'd like to see them.
and how much rpm @40 & 60mph?

I've done some calculations on gear reduction...if I remember, for every bump in ratio ie:4.1->4.3 there's a ~160rpm diff @60mph. So...stock [email protected] is 3,1xx rpm, yours should be around 3400.
I've got a build thread floating around the project section. I haven't really paid attention to freeway speeds and rpm's now that the speedo is off as well. I think speedo reads generally off by around 9% and keeping up with traffic around 70 mph is ~4500. It's really buzzy.
 

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sorry to bump an old thread but my friend has a kia sportage front diff lying around somewhere.
just wondering does it have to be any particular model of kia sportage?
this one is out of the newer 2nd gen model from 2004 on.
thanks.
 

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I am bumping this because of search.
Stormin Norman, How does the Diff feel mounts feel?
Should probably just get delrin mounts instead, they will damp a little vibration compared to aluminum and they're a little lighter.
 

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Haha the thuds from the diff and the vibrations sound like a good time. im sold! Aluminum it is. Im just scared of the delrin mounts deforming
 

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Lol the delrin mounts arent going to deform.
 

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Discussion Starter #15
Delrin will do the job just fine.

Some gear whine and some thuds now and then. Still happy here two years later.
 
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