Member
I've been reading the diff spotters guide on miata.net on how to ID a diff from looking at the axle holes but the way the pictures are labeled is confusing me. Can someone help me confirm the following?
This picture is a 4.3 open diff: https://www.miata.ne...iffguide/07.jpg
And this picture is a 4.3 Torsen diff: https://www.miata.ne...sen-closeup.jpg
Thanks in advance.
Michael Qiao
Northen NJ Region SCCA
East Street Racing / 2 Time National Champion
I've been reading the diff spotters guide on miata.net on how to ID a diff from looking at the axle holes but the way the pictures are labeled is confusing me. Can someone help me confirm the following?
This picture is a 4.3 open diff: https://www.miata.ne...iffguide/07.jpg
And this picture is a 4.3 Torsen diff: https://www.miata.ne...sen-closeup.jpg
Thanks in advance.
Well that is correct on torsen vs non torsen.. But No way to tell what ratio it is without counting teeth... 10:43 is 4:30, 11:43 is a 3:90.
East Street Auto Parts
Jim@Eaststreet.com
800 700 9080
Member
Well that is correct on torsen vs non torsen.. But No way to tell what ratio it is without counting teeth... 10:43 is 4:30, 11:43 is a 3:90.
Could I just spin the input plate and count the rotations of the axle? 1 driveshaft rotation to 4.3 axle rotations, right?
Michael Qiao
Northen NJ Region SCCA
Veteran Member
Veteran Member
Well that is correct on torsen vs non torsen.. But No way to tell what ratio it is without counting teeth... 10:43 is 4:30, 11:43 is a 3:90.
And a 10:41 is a 4.10 ratio
3.9 vs 4.1 vs 4.3, you better be accurate with your revolution counting
Dave Wheeler
Advanced Autosports, the nations most complete Spec Miata shop
Author, Spec Miata Constructors Guide, version 1 and 2.0
Building Championship winning cars since 1995
4 time Central Division Spec Miata Champion car builder 2012-2013-2014-2017
Back to Back June Sprints Spec Miata 1-2 finishes 2016 and 2017
5 time June Sprints winner in Mazda's
6 Time Northern Conference Champion Car Builder
2014 SCCA Majors National point Champion car builder
2014 SCCA Runoffs winner, T4 (Bender)
2014 Central Division Champion, ITS (Wheeler)
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2007 June Sprints winner, (GT1, Mohrhauser)
Over 200 race wins and counting.
www.advanced-autosports.com
dave@advanced-autosports.com
608-313-1230
Member
mike, to be 100% sure the center section has to come out of the aluminum housing. ring great teeth and the pinion gear teeth must be counted. simply looking at the type of hole when the cv axles are out, doesn't cut it. it may have been changed in a previous life.
Is this Nikki Coello's old black car that your asking about???
Marc Cefalo
www.planet-miata.com
570-262-1013 direct
#1 source for new and used Miata parts and accessories.
Polak Mafia Drug Lord and Avid Stamp Collector
Do all 3.9's have an 11 tooth pinion ?
Boris Badenof
Autotechnik's pet that sleeps in the crate outside
Veteran Member
Do all 3.9's have an 11 tooth pinion ?
I would say yes...at least in Mazda?
Ron
RAmotorsports
Polak Mafia Drug Lord and Avid Stamp Collector
I
I would say yes...at least in Mazda?
Yeah, only talking about our little cars.
Just curious if all 3.9's were 11-43 or was there a 10-39 setup ?
Boris Badenof
Autotechnik's pet that sleeps in the crate outside
Member
Well that is correct on torsen vs non torsen.. But No way to tell what ratio it is without counting teeth... 10:43 is 4:30, 11:43 is a 3:90.
And a 10:41 is a 4.10 ratio
3.9 vs 4.1 vs 4.3, you better be accurate with your revolution counting
mike, to be 100% sure the center section has to come out of the aluminum housing. ring great teeth and the pinion gear teeth must be counted. simply looking at the type of hole when the cv axles are out, doesn't cut it. it may have been changed in a previous life.
Is this Nikki Coello's old black car that your asking about???
Thanks guys I will crack it open and give it a count. This is for a new diff that I am picking up. My car currently is confirmed to have the 3.9.
Marc - I am not sure if Nikki Coello is a previous owner. This car came from the midwest. There's a few names in the log book but I don't remember them off the top of my head other than the last owner. I just ran it this weekend at July Sprints @ WGI - I was the guy parked next to Mr. Fetch. The car was in your shop earlier this year to do a non-restrictor dyno and setup. 
Michael Qiao
Northen NJ Region SCCA
Veteran Member
Do all 3.9's have an 11 tooth pinion ?
Yes.
For faster reply than PM: miataboxes>>>AT<<<gmail>>DOT<<<com
Veteran Member
I've been reading the diff spotters guide on miata.net on how to ID a diff from looking at the axle holes but the way the pictures are labeled is confusing me. Can someone help me confirm the following?
This picture is a 4.3 open diff: https://www.miata.ne...iffguide/07.jpg
And this picture is a 4.3 Torsen diff: https://www.miata.ne...sen-closeup.jpg
Thanks in advance.
96-97 T-2s, and *possibly* some JDM T-2s, will not have the characteristic washer look to them.
For faster reply than PM: miataboxes>>>AT<<<gmail>>DOT<<<com
Veteran Member
^^^ Straight hole through will be a T1 or early T2 as Saul points out!
Ron
RAmotorsports
Veteran Member
These videos are reposts from other threads, but the version on left will have a 4020 prefix on the serial number. Version on the right is more common, will have 4030 prefix. Both are legal for any 1.8L Spec Miata.
I fail to mention in the above video that the "coating" is from the factory and is nothing nefarious. Later factory Torsens have no coating at all, as shown in second video.
For faster reply than PM: miataboxes>>>AT<<<gmail>>DOT<<<com
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