XS Hack

There is a lot of information about how to mate a FE motor and the stronger type 2 or "R" transmission. Some people have been welding adapter plates, but that seemed to complicated to me. I knew there must be a Mazda factory combination that would work.

After a severe amount of googling, and lost sleep, I stumbled on a Australian build thread. In that thread There was a single picture of the FE-DOHC bolted to a R trans. That fellows build alerted me to the fact that B2600 came with R series transmissions and that G (B2600) and F motors have similar bellhousing patterns. So, I bough a B2600 bellhousing and What do you know? It all fits right together:



So the assembly consists of:
RX7 FD transmission (for proper shifter placement and gear ratios)
B2600 bellhousing, clutch, flywheel, pressure plate, starter, etc..

There is plenty of pilot bearing engagement, and the b2600 flywheel bolts right up to the F motors crankshaft.

The B2600 flywheel is a fair bit bigger than a 1.8 miata or the 2.0 FE, as is the bellhousing to go with it. I had to trim the sharp corner off the bellhousing where the starter bolts in, to help with firewall clearance. so the Starter will only be held in by two bolts. the bellhousing bosses are very thick where the bolts go through, so I had to buy longer ones than what came out of the kia assembly.

XS Hack

Here is another angle. I cut off the sharp corner of the starter pocket, the with the bolt hole that is furthest from the crank centerline.



and another, the whole assembly

18psi

iTrader: (76)

my buddy is attempting to do the same thing as you. he'll be overjoyed to see these pics.

good job.

please post as much info as you go about this as possible

Stealth97

iTrader: (5)

Wow, awesome information. Thanks for sharing

Stealth97

iTrader: (5)

Apparently the transmission fits a 4g63 also if someone is interested in a swap http://projectzerog.com/rx7transmissions.shtml

Dot3

iTrader: (1)

In.

XS Hack

I will be sure to keep everyone updated on any progress. The only thing I haven't checked is clutch engagement on the splines. The spline pattern is the same, however, the B2600 input is a tad shorter- I think a quarter inch or less. I will verify all that this week. Easiest solution would be swap inputs, or just have a little milled off the bellhousing face (remember it is very thick).

Yes, the trans came behind a mitsu engine for the first year or two in the b2600. This is the later bellhousing. The trans are similar, mazda just made a bellhousing to suit the mitsu engine before designing there own 2.6 engine.

m2cupcar

iTrader: (5)

That's the problem. I bolted up the bongo housing and RX R box to an FE block years ago and noticed the excessive distance between the shaft end and crank. As it sits there is <10mm engagement of a near 30mm spline depth when the clutch sits against a stock flywheel.


Then JoePianka put the two R trans side-by-side and confirmed this in Yank's build thread.


And if you bring over the truck R input shaft there's this:
And once it is in there, you have the crappy first gear.

I considered getting a flywheel made to spec - that would make up the 10mm the RX shaft lacks. BUT that would also reduce the area available for the larger clutch/pp.

concealer404

iTrader: (3)

Heh dammit... you just let the world know what i'm doing for my F2 Miata...

m2cupcar

iTrader: (5)

A custom flywheel?

concealer404

iTrader: (3)

Highly doubtful. You posted why i wouldn't need it above.

Sounds like worst case scenario i need a TII trans, B2600 bell, and B2600 input shaft.

m2cupcar

iTrader: (5)

Ah- the granny gear solution.

duffbuster243

iTrader: (1)

That picture is shown with an automatic flywheel, this needs to be more looked into with a proper manual flywheel bolted on that engine.

concealer404

iTrader: (3)

Not a big deal with a 3.23 rear end.


That setup is confirmed to bolt up and work correctly on an F2 either way.

What weirds me out is that in FWD-land, the FE3 is a direct swap for an F2. No weirdness with clutch/trans/mounts, none of that.

Strange that it's not so in RWD-land.

m2cupcar

iTrader: (5)

I only think it's because the FE never came oe in rwd. If it did, then Mazda would've just cut the tip off the input shaft as needed. I assume you'll be making some kind of compensation for the shifter location.

concealer404

iTrader: (3)

The Kia crank is different, then?


And yes, i'll make some kind of compensation. I have a sawzall.

m2cupcar

iTrader: (5)

The kia crank is indeed different though I don't know the specifics. Yank would- he's running the kia engine. The sportage also had a different transmission.

XS Hack

I will be really busy for the next two weeks, so, there will be little time to move forward with this. However, M2cup, My RX7 input shaft does not look like yours. Mine is from a FD, not FC. I think this makes a difference.

The spline looks significantly longer on my trans, compared to the pictures you posted above. More like the truck version. There is more than 35 mm of spline exposed with the bellhousing installed, about 37mm available.

In the pictures you posted, it looks like the "pilot bearing snout" on the input (RX7 FC) won't engage the pilot bearing. Mine is well engaged as you can see in this picture. The rusty part is the part engaging the pilot bearing when installed, about 12mm total. The snout on the FD is about 27 mm, on the B2600 it is 25mm. I will do more measurements when everything comes apart again. i will also install the clutch assembly and check clearances.



I have no way to prove it, but I think the input shaft in the FD is different than the FC. The FD has a pull style clutch, where the FC had a more standard push style I think. I can tell you the FD bellhousing is completely different from that in the FC. This could lead to changes in the input shaft.

m2cupcar

iTrader: (5)

That photo is of the FC R trans (box/mid and tail) mounted to the bongo front/bell housing. It's the bongo's shaft sleeve that's so much longer. When the Rx7 box is mounted to the original front/bell housing from the Turbo II it looks like your photo. Photos below show the measurements for the truck R and Rx7 R input shafts starting at the box. I hope your's was measured the same- for everybody's sake and the FD is indeed a longer shaft.


Top- Truck : Bottom- FC Rx7 TII


Truck


FC Rx7 TII

XS Hack

I finally had time to put the flywheel on the engine and slip a clutch disc in the trans before bolting it all together. The clutch disc has more than adequate travel on the splines! I'm attaching a picture of the clutch in its most forward position, as it would be when seated against the flywheel. As you can see, with the clutch seated against the flywheel there is still about 9mm of spline left.



So the winning combination is B2600 flywheel, clutch, pressure plate, starter, and bellhousing with the FD RX-7 transmission. On the KIA engine i had to remove the dowel pin from the crankshaft, because the B2600 flywheel did not have a hole for it. Of course you could drill a dowel hole with some careful measuring.