(TRANSMISSION) How To: Swapping a S4 N/A tranny into an FB
 

This tread is going to follow the procedure of installing a S4 N/A transmission into your FB chassis. I know this has been covered before but i thought a nice write up with a few pictures would be nice.

I'm sure we all know how to remove the stock transmission from the car. If not post up and I will do a write up for that part of the swap.


Once you have removed your transmission and placed on the ground remove the 8 12mm bolts holding the tailshaft housing to the gear box. Pictured below with green arrows.
Next remove the four 10mm bolts from the inspection plate from the side of the shifter housing. Inside of there you will find the metal block that the shifter ball sits in that connects to the shifter linkage. On the side of this you will find one 10mm set bolt that you will need to remove. Pictured below with a yellow ring and arrow. Once that is done then you can take large screw driver or dull chisel and tap up on the edge of the tailshaft housing to free the silicone seal made by the factory. Once the seal is broken you can lift the tailshaft housing off the body of the transmission, while lifting up reach inside and rotate the shifter linkage out from the gear selector forks. Now that the tailshaft housing is removed from the body you will need to remove a snap ring from above the speedo gear, now you can remove the speedo gear off of the tailshaft. Keep the speed gear as you will need to install this onto your FC transmission tailshaft. Pictured below with a blue ring and arrow.


Follow the above instructions for disassembling your S4 N/A transmission. When you get to removing the metal block from the shifter linkage you will encounter that there is no bolt but there is however a set pin that needs to be removed. This pin will only come out one way so make sure the rolled pin hole is rotated down towards the tailshaft housing. Use a punch to remove this pin.

Now that you have both transmissions apart you can start to reassemble your new hybrid FC/FB transmission. Start by installing your FB speedo gear (which is orange, FC is yellow) onto your tailshaft, then reinstall the snap ring above it. Clean the mating area of the FC gear box and the tailshaft housing from your FB. Once clean you can apply some new RTV silicone sealant to the area. This doesn't have to be a large bead just enough to create a small gasket between the two pieces. Now you can begin to install the tailshaft housing. While lowering your housing make sure to place the shifter linkage into the shiftrod forks on the box or you may have to lift the housing back up to do so. Pictured below with a red ring and arrow. Now replace the eight 12mm bolts back into the transmission and tighten down. With the transmission bolted together you can install the metal shifter block back onto the shifter linkage. Now with that done you can replace the 10mm set bolt through the block and linkage. Clean the inspection plate and mounting surface of the shifter housing and run a bead of silicone to seal the area. Replace the four 10mm bolts to secure the plate to the housing.

Time to reinstall your new transmission into you car.

Please note on the swap you will also need to acquire a stock S4 clutch slave cylinder since you will need its longer length to fully engage your clutch.


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Nice write up.

1 thing that I have never had to do though is use a 2nd gen slave cylinder. I have used as probably others the 1st gen slave cylinder with no issues.

What are the two holes on the side of the S4 N/A trans that you circled. They look like some kind of inspection hole or something....

BTW What's an S4 NA?

13b off a FC?

yep...im installing an s4 block along with doing this trans swap hopefully this weekend...im waiting on parts now.

the fc trans i have didnt come with the shifter on it....so do i have to worry about the pin i have to punch out?

it should still have the shifter linkage and box. Look at the pic of the s4 tranny and at the end of the tailshaft housing you should see the box. remove the inspection plate. better yet post a pic of your tranny

Oh ok i understand now....thanks for the write-up again bro!

79-83 transmission do not have the vent holes but 84-85 models do.:)

my fb transmission is out of my 85. its original to the car never been swapped. Could be that us canadians got a different tranny

I honestly don't know if they would of used a different transmission in Canada. I would think not. How do you know it's the original trans. Did you buy the car new?

My first rx7 was a 84 gsl and it did not have vent holes and this is my second a 85 gsl. I'm not the original owner on both so maybe they were both swapped for an older trans

Sorry I am a little confused, I am doing this right now and I thought you had to use the the FC trans, FC tailshaft, FB shiftbox and cut down the FC shift tube and rod and drill a new hole. Or is this for a T2 trans only. And again sorry if I am wrong but I am a little new with all this RX stuff.

no you use the fc bell housing, fc shiftbox, fb tailshaft....so that its the same length as the fb trans but has the fc gearing.