what is needed for the Kia 4.78 Gear ring and Pinion to install into a FC rear diff, the Pinions shaft is much Shorter than the FC, or is that swap just for 1st Gens cause its a Direct swap for 1st Gen rear ends, if anyone has done it or have any real info chime in, i have a kia sportage 4.78 and pinion

 

Based on what I read in these threads, it seems that dropping in the kia rear end is the easiest choice.

I have no idea about this but I found all of these threads pertaining to what you are asking

https://www.rx7club.com/1st-generati...-gears-957021/

https://www.rx7club.com/1st-gen-arch...pinion-507123/

https://www.rx7club.com/2nd-generati...ar-end-699004/

https://www.rx7club.com/1st-generati...nto-se-201736/

https://www.rx7club.com/1st-generati...-years-882408/

member selling a 4.78 rear end. PM him for info?
https://www.rx7club.com/1st-generati...-4-78s-955399/

 

Ive read about this, but have yet to find a thread where somone does it.
Do it. All you would need is to see if itll fit n/a or tii and just swap the ring, since the pinion is obviously too small. Might even find a way to keep an lsd.

 

Same here. All of those threads always end up with references to people having done an FC install but I could only find FB install pics. The claim is that it is a drop in mod.

 

1st generation RX7's have a short pinion gear, just like the KIA. They also have the same 7" rear end (RX8's and RX7's have 8"rears).

To use the KIA 4.77 gear set into a FC is different, you need to do 1 of 2 things.

1) Have Mazdatrix or another fabricator graft the gear off the KIA pinion onto the longer FC3s pinion.

Mazdatrix already does this and has it available, you must send in the long pinion for them.

Other shops can do it too, check with old school race shops and most can do this. It's popular in the SCCA world.

2) Swap in the short pinion section of the rear in from a Miata or a 1st generation RX7 and make a custom front mount, driveshaft, etc.

Most people do #1, never seen or heard of anyone actually doing the front one.

FWIW. Ronin Speedworks sells a swap kit for a 8.8 rear, you'll have a plethora of gear choices to choose from with that route and a very cheap rear end in the LONG haul, initially it'll be 1000-1500 dollas.

I hope this helps.

 

Mazda basically makes two differentials.

the M type, which is a 7" ring gear and is found in the R100/rx2/3/4/5. the 79-85 Rx7 also uses it. also the 94-2005 miata. basically Mazda puts it in every non turbo rotary, or 4 cylinder non turbo RWD car/truck. Kia and Honda also make it, Kia used it in the sportage, and Honda uses it in the S2000. honda uses it with way more power than Mazda does.

the P type is an 8" ring gear, and is found in the FC turbo, FD, Rx8, Mpv, 929. basically any turbo, or V6 RWD car.

the non turbo FC uses the M type, but since its an FC it uses a weird long pinion

 

I'm in the process of building a "kit" to mount a sportage diff in an FC. The bolts all line up pumpkin to FC cover. Just needs the "kit" part which is the fabbed mount adapter, a longer driveshaft (84-85 shaft MAY be a drop in shaft) & sportage diff to work.

 

That's badass.

 

Thanks for the Info Guys, Landon its me DAve, i bought the kia Pinion and gear from you bro lol