Race Car Tech Discuss anything related to road racing and auto X.

RX7 and Miata diff interchange question

Old 05-12-04, 03:45 PM
  #1  
Senior Member
10 Year Member
Thread Starter
iTrader: (4)
 
RX744CSP's Avatar
 
Join Date: Apr 2004
Location: Charleston, SC
Posts: 340
Likes: 0
Received 0 Likes on 0 Posts
RX7 and Miata diff interchange question

I've got a GSL (not SE) limited slip axle, and I can get a '91 Miata dirt cheap. I was considering putting the GSL limited slip in the '91 diff, anyone ever done this? There's lots of info on second gen LSD's in 1.8 Miata, but nothin', and I mean nothin', on the earlier stuff.

TIA.
RX744CSP is offline  
Old 05-12-04, 04:23 PM
  #2  
Rotary Freak
10 Year Member
 
Blake's Avatar
 
Join Date: Aug 2001
Posts: 2,267
Likes: 0
Received 0 Likes on 0 Posts
I might be having a brain fart, but aren't the 84-85 (i.e. "big axle") 1st gen and 86-91 2nd gen NA LSDs identical in size (axle, ring gear)? In fact, I think the clutch-style LSD is the same unit from 84-88, when they went to viscous, and even then are swappable with the later units. Someone correct me if I'm wrong.

Last edited by Blake; 05-12-04 at 04:29 PM.
Blake is offline  
Old 05-12-04, 04:35 PM
  #3  
Senior Member
10 Year Member
Thread Starter
iTrader: (4)
 
RX744CSP's Avatar
 
Join Date: Apr 2004
Location: Charleston, SC
Posts: 340
Likes: 0
Received 0 Likes on 0 Posts
Yes, there's lots of stuff on the later diff swap out there. My question is about the earlier (6" ring gear) Miata diff. I'm trying to do something on the cheap with what I have available, and if the GSL diff will go in the early Miata housing with the early 4:30-1 axle ratio, I'll be well on my way. If not, oh well it was a good try.
RX744CSP is offline  
Old 05-12-04, 04:47 PM
  #4  
Rotary Freak
10 Year Member
 
Blake's Avatar
 
Join Date: Aug 2001
Posts: 2,267
Likes: 0
Received 0 Likes on 0 Posts
Oh, you are getting a 1.6 Miata diff?! I get it, now -- I was thinking you meant "earlier" wrt RX-7s (i.e. 1st gens vs. 2nd gens); not Miatas (1.6 vs. 1.8). No, the 1.6 stuff is not compatible with anything RX-7. All 1st gens had the same ring and pinion, with the only difference being "big" vs. "small" axles, which only affected LSDs (side gears, at any rate). 2nd gen NAs were the same as 1st gens, except for the long pinion.

Last edited by Blake; 05-12-04 at 04:50 PM.
Blake is offline  
Old 05-12-04, 05:58 PM
  #5  
EX Pres of DFW Drunks
10 Year Member
 
rx7gslse's Avatar
 
Join Date: Feb 2001
Location: DFW, TX/Mexico
Posts: 8,132
Likes: 0
Received 1 Like on 1 Post
well I don't know how helpful, but here's a ton of info on diff interchange..

http://members.aol.com/solomiata/MiataVLSD.html
rx7gslse is offline  
Old 05-13-04, 07:52 PM
  #6  
Rotary Freak
10 Year Member
iTrader: (6)
 
Kill No Cone's Avatar
 
Join Date: May 2002
Location: Olympia WA
Posts: 1,982
Likes: 0
Received 1 Like on 1 Post
I don't think the 6" Miata 3rd member will work. I think you have to go to the 7" and it only wiorks for the 84 -85 cars. When you go to the 7" Maita you are stuck with the 4.10 gears, unless you are really lucky and get the 4.30 which is rare.
Kill No Cone is offline  
Old 05-14-04, 01:49 PM
  #7  
Rotary Enthusiast
 
Maguire's Avatar
 
Join Date: Jun 2002
Location: Louisville, Ky
Posts: 1,059
Likes: 0
Received 0 Likes on 0 Posts
what your probably going to want to do, is get a 3rd member out of a 94-97 miata with a torsen lsd. If you cant find one with a torsen, buy an open diff. then you can use any 7" rx7 ring gear. Youre also going to need the 94 driveshaft and half shafts. from what i understand, it all bolts right in.
Maguire is offline  
Old 05-14-04, 09:46 PM
  #8  
Rotary Freak
10 Year Member
iTrader: (6)
 
Kill No Cone's Avatar
 
Join Date: May 2002
Location: Olympia WA
Posts: 1,982
Likes: 0
Received 1 Like on 1 Post
You can bolt the 94-97 Maita 3rd member into a 84-85 Rx7 housing without any other mods.
Kill No Cone is offline  
Old 05-14-04, 11:57 PM
  #9  
Rotary Freak
10 Year Member
 
Blake's Avatar
 
Join Date: Aug 2001
Posts: 2,267
Likes: 0
Received 0 Likes on 0 Posts
I think he is buying a 1.6L Miata and simply wants to know if he can upgrade it with an RX-7 LSD; not put a Miata diff in an RX-7. Unfortunately, that is not possible because all the 1st and 2nd gen RX-7 stuff is incompatible with the early Miata stuff. In other words, he is SOL unless he upgrades to 1.8L Miata rear end components or finds another LSD donor (323?).
Blake is offline  
Old 04-05-10, 06:41 AM
  #10  
Full Member
5 Year Member
 
Fozzybeardude's Avatar
 
Join Date: Oct 2007
Location: Bothell
Posts: 91
Likes: 0
Received 0 Likes on 0 Posts
I know this thread died like 6 years ago but here it is.

I'm looking for a way to get a lower ring and pinion set than a 4.30 into my 2nd Gen RX7. Can I swap the 1.8 Miata parts into the RX7?

I race circle track and already have the '89 LSD with the 4.30 gears and am looking for 4.77 or lower.

Any ideas here would be appreciated
Fozzybeardude is offline  
Old 04-05-10, 08:37 PM
  #11  
Senior Member
5 Year Member
iTrader: (3)
 
Join Date: Sep 2004
Location: San Luis Obispo, CA
Posts: 548
Likes: 0
Received 0 Likes on 0 Posts
Originally Posted by Fozzybeardude View Post
I know this thread died like 6 years ago but here it is.

I'm looking for a way to get a lower ring and pinion set than a 4.30 into my 2nd Gen RX7. Can I swap the 1.8 Miata parts into the RX7?

I race circle track and already have the '89 LSD with the 4.30 gears and am looking for 4.77 or lower.

Any ideas here would be appreciated
The Aluminum part of the housing is the same, so it will bolt up to the mounting points on the 7.

I suppose then all you'd need is a custom front axle mount and a longer drive shaft.

I've been thinking about this myself, personally, but I dunno what the cost/effort would be over having 4.88s or 5.12s made.
HotRodMex is offline  
Old 04-05-10, 10:51 PM
  #12  
Lives on the Forum
10 Year Member
 
Black91n/a's Avatar
 
Join Date: Sep 2003
Location: BC, Canada
Posts: 5,707
Likes: 0
Received 1 Like on 1 Post
FC racers, due to class restrictions, typically just graft the Miata/FB pinion gear onto the long FC pinion shaft so that it's a bolt in conversion. If I were doing it without the class rules restrictions, I'd use a Miata housing and lengthen the driveshaft and come up with a different front mount.
Black91n/a is offline  
Old 04-05-10, 11:06 PM
  #13  
Polishing Fiend
iTrader: (139)
 
CrispyRX7's Avatar
 
Join Date: Apr 2001
Location: MD
Posts: 3,296
Received 5 Likes on 5 Posts
Maybe this will help.
http://www.reganrotaryracing.com/fc/fcpart17.htm
I've been using a Miata torsen with a 4:30 R&P for a few years without issue.
I'd see no reason why I/you couldn't run a 4:77 or 5:12 with this combo.
Regards,
Crispy
CrispyRX7 is offline  
Old 04-07-10, 09:20 PM
  #14  
Full Member
5 Year Member
 
Fozzybeardude's Avatar
 
Join Date: Oct 2007
Location: Bothell
Posts: 91
Likes: 0
Received 0 Likes on 0 Posts
Thanks for the link Crispy, that is some good info. However, I'm hoping to switch housings to the short pinion to eliminate the cost of grafting 2 pinion gears together to make one.

I wish they would have just made some lower ratio ring and pinions for the long pinion design.

Black91 - I agree that is the way to do it. I'm using the GTUs 4.30 LSD and think I can trade it straight across for the 1.8 Miata Torsen diff.
Fozzybeardude is offline  
Old 04-07-10, 11:51 PM
  #15  
Lives on the Forum
10 Year Member
 
Black91n/a's Avatar
 
Join Date: Sep 2003
Location: BC, Canada
Posts: 5,707
Likes: 0
Received 1 Like on 1 Post
I've read that the aluminum housing part is the same between the Miata and the FC, but the bushings are slightly different. So it should be a more or less bolt in swap. I've got a 1.8 Miata Torsen in my car. The S5 diffs are all viscous, so it's probably not terribly effective. A torsen should be an improvement.
Black91n/a is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
astrum
2nd Generation Specific (1986-1992)
24
11-15-17 08:44 AM
smikels
Rtek Forum
4
05-12-16 12:34 AM
Professorpeanutrx7
New Member RX-7 Technical
5
08-15-15 01:38 PM


Thread Tools
Search this Thread
Quick Reply: RX7 and Miata diff interchange question


Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: