Nice writeup, good job.

 

Honestly, I can say that's one good thing about living in Tucson. None of these people can drive!

I am almost positive I can call 1 guy first thing in the morning and get one or two diffs!

 

4.78 will run at a lower RPM than a 4.44. There is approximately 2K RPM difference between the two gears at 85 MPH

 

did you mean higher RPM?

 

nope. My flared RX-3 has a 4.78 but it runs at a lower RPM (freeway speed) than my FB with 4.44. Keep in mind that both cars are equipped with GSL-SE trannies and 15" rims. And 100%, your speedo will be off.

 

That's not really possible if they have the same drivetrain except for ring and pinion.

 

I cant figure it out why the 4.78 runs at lower RPM. can someone explain that?

The only issue I can think of is the ignition:

RX-3: MSD 6A/coils direct fire.
FB: MSD 6AL/FC coil direct fire

 

Thanks for Clearing this up. Now we just need a Miata LSD install.

 

this is very odd wacky..... you sure you wasn't when installing the 2 gears





caz it is for sure backwards... unless your tires are like 26 inch tall on the rx3

 

lol. I will take it apart once Im done working with my 73 RX-3 wherein Im installing another set of kia 4.44.

 

It's got to be somewhere from the tach to it's hook up. That 2000 rpm difference is way more of an increase than would be seen from that small of a gear change.

 

Hey, technically I should be able to just drop these gears into a dif from an 83 right? I mean as long as I keep the actual pumkin the same. Just a gear swap.

 

Both tachs are connected to the MSD boxes, not coil. In fact, with the RX-3, the stock tach is in trailing and autogage 10K in MSD box; both reads the same.

 

yes the gears will swap over 100% if you put them in the rx7 pumkin... they are both 7inch

 

In case there is a smart *** out there. the KIA's rear diffy is 7.5" but its a 4.78 gear

 

Perhaps someone had previously swapped an FC trans into the SE you got the trans out of. FC trans had as high as a .69x 5th gear (too lazy to look for the exact number).
That could explain why the lower diff ratio still has the lower RPM on the highway.

 

i thought the rear was the 7.5 and the front was a 7...thanks for the correction

 

.

 

4.44s front B2600 front diffs are around too.

 

ok, here's the botton line based on my experience.

pre-97 KIA and B2600 4x4 (all years? I dont know) = 4.44
97+ KIA = 4.78

 

sweetass. 4.44 is what i wanted. time to call some junk yards. thanks guys.

 

you need an 87-88 b2600 4x4....i know the 5pd works, not sure about other ones. not sure if the year range is broader or not.

 

Any other modell kias that will fit? ive already tried and no sportages around here

 

all i have to say you are the men. you answer all my questions. hunt for the kia gears has begun

 

Me on the other hand, Im tired of it. But here's a tip tho. When you find it, work on the passenger side front axle, then unbolt it from the frame so that the whole diffy will collapse on the passenger side. this way, you dont have to deal with the drive side.