I can get this, and have JR make it fit. I posted on RX7Club too as it seems to have more hardcore racers than here. The feeling I got from one member is that it will work. Its sort of a "must have" mod if youre gonna autocross.



I amgoing to order this gear set and give it a whirl. My street driving days are coming to an end.... or I am going to have to learn how to swap out gears and learn how to do it with ease.





http://www.mazdamotorsports.com/wcsc...12-27-110A.JPG

Jim, You will be essentially running a NA rear now. I have been modding my to handle the output of the PP and I have a few tricks up my sleeve that JR may not know about https://www.nopistons.com/forums/pub...IR#>/smile.png

Cruising at 3600 RPM might mean you avoid that annoying drone at 3000 RPM! https://www.nopistons.com/forums/pub...#>/biggrin.png



The 4.77 have a spacer between the diff and the ring gear, and a kind of collar that fits over the bearing race next to the gear on the pinion shaft.



I don't have a stock one in front of me to compare, but I'm thinking the only way it's stronger is right at that bearing race next to the pinion gear, as it would be about 4mm larger diameter, and the radial load at this location is higher due to a smaller diameter pinion gear on the 4.77 gear set. The ring gear is still 8" outside diameter with 43 teeth.



I would SUSPECT the 4.3 set uses this ring gear with a 10 tooth pinion, and the 3.9 set uses it with an 11 tooth pinion. This would likely explain the spacer behind the ring gear on the 4.77 set, as it's needed to engage the smaller 9 tooth pinion used for this ratio. But this is a bit of an educated guess until I take apart the stock one.https://www.nopistons.com/forums/pub...IR#>/smile.png

there are 3 different mazda diffs.



the 6" ring gear diff, its really only used in the 323gtx and 90-93 miata, T type



the 7" ring gear diffs, these are used in almost everything non turbo, r100, the trucks, all the NON turbo rx7's, this rear has all the cool gear sets, also the kia sportage uses these diffs and come with a $300* 4.77 gear set. the b2600 trucks have a 4.44, miata is 4.3 some years, fb's are 3.9 or 4.1, etc etc. this is the M type diff



the 8" ring gear diff, or P type, is found in the rwd turbo or v6 cars. turbo fc, fd, mpv, etc. the complication here is that the fc has the long pinion gear so nothing else fits without some pretty technical cutting and rewelding of the pinion. this is where the fc sucks the most as the only 3 ratios offered for it seem to be 3.9,4.1 and 4.3.





*we dont have kia anymore, so the price is gonna be higher

So the FD doesn't use the longer pinion?

nope, the fc uses the wierd one. we looked at putting a short pinion diff in the fc, you'd have to come up with a front mount for it but it fits

so which ones are compatible with fd's and fc's? just the type p?

the fd is a p type, like the rx8 which has 4.44



the fc's are compatible with only themselves, unless you can cut and lengthen the pinion gear. the na fc uses the m type diff, and the turbo fc uses the p type diff

Don't forget the odd 7.5" diff, which looks like a 7" until you try to swap the gearsets.

[quote name='Jims5543' date='Mar 13 2005, 07:59 AM']I can get this, and have JR make it fit. I posted on RX7Club too as it seems to have more hardcore racers than here. The feeling I got from one member is that it will work. Its sort of a "must have" mod if youre gonna autocross.



I amgoing to order this gear set and give it a whirl. My street driving days are coming to an end.... or I am going to have to learn how to swap out gears and learn how to do it with ease.

http://www.mazdamotorsports.com/wcsc...12-27-110A.JPG


[/quote]



From what I understand the NA rear has a smaller diameter ring gear, 7" I believe. The turbo ones are 8" rings so it won't just bolt onto your car. You would have to run a NA differential with that ring/pinion setup your posted.