infernosg's S5 N/A Build

[RETed]

Originally Posted by infernosg

Something interesting to note; the Miata 2nd gear is double-synchro'd:

Is the ratios like the FC ratios?
If so, this makes sense...
If the ratios from 1st to 2nd are pretty wide, then the double syncho would make for a smoother shift between the two, especially at high revs.
FC's are known to scratch the 1st -> 2nd gear shift when getting close to redline.
Also, trying to downshift and rev match is a royal PITA from 2nd -> 1st, although most people don't need to, but some really low speed autocross course might...

Another odd difference is the RX-7 reverse gear is straight cut whereas the Miata is helicall.

This makes sense too...
FC's tend to scratch going into reverse gear...
A band-aid procedure is to shift into 1st (or 2nd) first and then into reverse on the FC.
This seems to help.

Kudos and documenting this and posting the info!


-Ted

[diabolical1]

Originally Posted by tweiss3

Looks like a great weekend of work. You have more guts than I do, transmissions scare me.

this ...

Originally Posted by RETed

Kudos and documenting this and posting the info!

... and this.

[infernosg]

Originally Posted by RETed

Is the ratios like the FC ratios?
If so, this makes sense...
If the ratios from 1st to 2nd are pretty wide, then the double syncho would make for a smoother shift between the two, especially at high revs.
FC's are known to scratch the 1st -> 2nd gear shift when getting close to redline.
Also, trying to downshift and rev match is a royal PITA from 2nd -> 1st, although most people don't need to, but some really low speed autocross course might...

Everything I've read about the Miata gear ratios has 1-3 being taller, but closer together than the RX-7 ratios. 2nd gear gets slammed quite a bit both up from 1st and down from 3rd so I can see why Mazda added the second synchronizer. I can see this being even more advantageous in an RX-7 application due to the higher engine speeds. It's a more complicated design, which means more points of failure so I'm curious how it'll hold up. It's a completely different transmission, but does anyone know if Mazda made this same change to the Type R transmission in the FD?

Originally Posted by RETed

This makes sense too...
FC's tend to scratch going into reverse gear...
A band-aid procedure is to shift into 1st (or 2nd) first and then into reverse on the FC.
This seems to help.

I recall having this issue. Fortunately I spend very little time in reverse. It was just something interesting to note. These transmissions are all fundamentally the same so it's interesting to see all the little internal revisions Mazda did throughout the years. My transmission came out of a '96 Miata so it's possible other years are different. I've heard the latest ('04?) Type M's are the best to get because they have the most amount of improvements.

Originally Posted by RETed

Kudos and documenting this and posting the info!


-Ted

I'm going to try to take more pictures during the reassembly process. My goal is to use them in reverse in a "how-to" thread. There are many other small differences between the transmissions (e.g. snap rings, bearings, etc.) and I'll try to reference them all there.

In other news the input shaft modification is supposedly done so I'm going to pick that up after work today. I gave them the dimensions from Mazdatrix's website but I'm still a little worried it won't turn out right. Just an annoying trust issue I have I guess...