RX7 BOX SWAP

[OLD FART]

Has anyone got one up and running in a Staz??
I was wondering what the difference was in gear speeds (provided you have the speedo calibrated correctly ) and the shift quality above 5k and the cost to have the rx7 yoke welded on to the drive shaft ??
I think that Dave is doing this conversion to Steves TC widey atm

Do we have a resident boffin or maths wiz that can do a comparison chart ??

[Lunacy]

Rad, JAS has put a b2600 box in his gold car, and i have just bought one as well. Trick is finding the right bellhousing.
As far as i know JAS is happy with his, although he said its prob better to run the 3.545 diff gears in a street car rather than the 3.90s.
3.90 for mine though as its track/targa car only :)
B2600 same as rx7 except puts gear shifter in right position where as the rx one is 6" further back.

[WANTSOM]

Rad,

You need to rrad through this (if you havent already) :beer

http://www.projectzerog.com/rx7transmissions.shtml

[OLD FART]

Thanks Bryce & Greg Have been thru all the projectzerog posts and already have the G54 bellhousing .What model/years(in Oz ) B2600 boxes are the ones to get?? I was concerned with strength & shift speed/smoothness as the staz box is a bit baulky above 4k rpm's
Thought that I might get one to put in shed just in case

[JAS]

Hey Rad,

I'm using a B2200 box out of about a 90-92 model. You have to shorten the input shaft around 7mm or so but its an easy job (just on the B2200 box tho). You should have what ever you use stripped anyway so that the oil way for the front bearing can be moded. They suffer from lack of oil there and this is where most fail.

Some of the boxes come with 2 piece syncros but I don't know how you can tell them apart unless you strip the box.

The input shaft on the ute boxes have a better clutch spline too. They are around 15mm longer (towards the back of the box) than the RX7 boxes. Which suits the starion clutch spot on. I think if you used the RX7 box you would only get half the teeth of the clutch plate on the input shaft.

The shifter on the ute boxes are almost exactly the same distance from the front of the belhousing as the starion one's too.
And if you get a Ute box you can use the starion gearbox cross member. The RX7 boxes have the mount on a very odd angle. And need a custom cross member made.

Oh and I had to shorten the clutch fork where the slave cylinder pushes against it by around 15mm from memory. This was the B2200 fork tho.

I would go for the 3.54 diff ratio if I was going to do it again. The first gears are quite short and at 100Ks in 5th its doing about 3200rpm. Really depends on what you have planned for it I guess.

Come on over Rad and take my car for a spin. See how you like the mazda box compared to the starion :)

[OLD FART]

Would love to take you up on the test drive as we want to come over again in winter to see the snow
Thanks 4 all the tips and how is the shift compared with the wideys 5speed??
Cheers
Rad

[JAS]

Would love to take you up on the test drive as we want to come over again in winter to see the snow
Thanks 4 all the tips and how is the shift compared with the wideys 5speed??
Cheers
Rad

Yes for sure. Let me know when your heading my way. Be great to catch up again.

The shift is about the same as the widey. But I haven't used it above 4000rpm yet. It does feel stronger tho. Or that might be just my imagination

[RallyStarion]

I have been running an RX7 s4 box with an aftermarket close ratio gearset in the Rallycar for the last 3 years and it is fantastic, the std box was used for 200kms to see if any issues were going to arise but none appeared.
Off memory I had to shorten the shifter on the top of the box about 110mm and fabricate another rear support mount and the tailshaft was an easy fix to have made. The box is a tight squeeze in parts of the tunnel but thats not a real issue. I also made a short throw gearshift that make it the sweetest box to use.
I have given this box the hardest of times and am told it is good for around 500 hp. Having damaged the original sports option box a couple of times and not wanting to try and sort out a Hollinger conversion this was the best and cheapest option.
Very happy with the outcome.

Brian.

[JAS]

Oh and I forgot about the Reversing sensor. You will either have to heat the trans tunnel and push it out with a hammer or just run without one.
I think this only applies to the ute boxes tho.

[stariontron]

hey guys just a couple of questions on gearboxes if you dont mind;

are you saying that the b2600 gearbox is as strong as the turbo rx7 box?

is there much difference in strength between turbo and n/a rx7 boxes?

judging from what i've read in this thread, a b2600 gearbox will bolt straight onto the engine, be strong enough, and the shifter will be in the right place?

cheers

[redzone]

the main reason i like the RX7 box over the ute box is because the shift quality at high rpm is so much better. i did my apprenticeship at a mazda dealership and i remember customers always complaining about the shift quality of the commercial 5 speeds. the FC box is designed for rotary RPM's, and a lot of guys use them in high hp rotors! the RX7 box is also stronger than a W58..

also the FC ratios are almost IDENTICAL to the stock starion box, other than the 5th ratio which is .1 taller in the FC! so better economy on the highway..

i got the extension housing shortened for about $250, this is a common mod that the early rotor guys get done so it's easy to get done, you're not reinventing the wheel..

[redzone]

oh and the na and turbo FC boxes are practically identical, there are differences between series 4 and 5 though, the rear mount shape is the easiest way to pick the difference.

[docile]

What is this talk of a needing a custom cross member for the RX7 boxes? Is this because of the rear mount location? And if so, does the S5 or S6 box have them in the right place?

Additionally JAS has brought up the issue of the input shaft not being long enough on the RX boxes, is that really the case?

[mbrallying]

I heard a rumour that the rx7 gearset will fit the ute case. Can anyone confirm this???

[redzone]

i'd be surprised if they didnt, they're the same "family"