The Transmission / Differential FAQ

[Whizbang]

Updated: 7 Jan 2014

The following is a coming together of information for quick reference when looking for a gear ratio, transmission choice or any other information that may assist those looking to modify or repair there drive line. This thread will be updated periodically and reference to that will be via that date at the very top of this thread


Transmission Gear Ratios

Q. Can i use a Ford or Chevy transmission?
A. Yes, a couple of companies make adapters and bell housings to allow for a spread of transmissions including the Ford T5, various Chevy transmissions and Jericos.

See this thread here regarding swapping a T-5: T-5 Swap

For the Ford T5 see Rotaryshack or Kennedy Engineering.

For Chevy transmissions see J.W. Performance Transmissions Page 17

For Jerico transmissions see J.W. Performance Transmissions Page 17

For VW transmissions see Kennedy Engineering

Q. Are there aftermarket gear sets for my stock transmission case?
A. Yes,Pfitzner Performance Gearboxs (PPG) makes several options. OSGiken also makes sets for the FD3S and FC3S Turbo II.

Pfitzner Performance Gearbox

• 5 speed dog engagement gearset
• Series 1-5 billet shifter platform
• Short shifter assembly
• Hardened billet selector fingers

OSgiken

3 Speed Kit for the FC/FD:
1st: 2.714
2nd: 1.742
3rd: 1.267

5 speed kit for the FC/FD:
1st: 2.578
2nd: 1.772
3rd: 1.289
4th: 1.000
5th: 0.821

Q. What about the Miata gearset swap?
A. See this thread here for some good information: Miata Gears

Q. Can i swap an Rx8 Transmission?
A. Yes, but read this thread throughly first: Rx8 Transmission

Factory Transmission Ratios

Please note that the there can be variances in the fifth gear of the transmission depending on the sales market (Japan, USA and UK)

Mazda Rx2, Rx3, Rx4, Rx5 (Cosmo) 12A/13B Gearbox
1st: 3.380
2nd: 2.002
3rd: 1.390
4th: 1.00
5th: 0.791

Mazda Rx3SP 77-78 Gearbox
1st: 3.380
2nd: 2.002
3rd: 1.390
4th: 1.00
5th: 0.791

Mazda Rx-4 77-78 13B Gearbox
1st: 3.380
2nd: 2.002
3rd: 1.390
4th: 1.00
5th: 0.791

Mazda Rx-5 (Cosmo) 77-78 13B Gearbox
1st: 3.380
2nd: 2.002
3rd: 1.390
4th: 1.00
5th: 0.791

Mazda Rotary Engined Pickup 74-75
1st: 3.683
2nd: 2.263
3rd: 1.397
4th: 1.000

Mazda Rotary Engined Pickup 76-77
1st: 3.683
2nd: 2.263
3rd: 1.397
4th: 1.000
5th: 0.862

Mazda Miata Gearbox
1st: 3.136
2nd: 1.888
3rd: 1.330
4th: 1.00
5th: 0.814

89-93 B2600 "R" Transmission
1st: 3.730
2nd: 2.158
3rd: 1.396
4th: 1.000
5th: 0.816

Mazda Rx-7 early 12A Gearbox (4spd)
1st:
2nd:
3rd:
4th:

Mazda Competition Rx-7 Gearbox
1st: 2.350
2nd: 1.608
3rd: 1.240
4th: 1.00
5th: 0.881 or 0.839

Mazda Rx-7 79-83 12A Gearbox
1st: 3.674
2nd: 2.217
3rd: 1.432
4th: 1.00
5th: 0.825

Mazda Rx-7 79-85 Automatic Transmission (L4N71B)
1st: 2.458
2nd: 1.458
3rd: 1.00
4th: 0.720

Mazda Rx-7 84-85 12A Gearbox
1st: 3.622
2nd: 2.186
3rd: 1.419
4th: 1.00
5th: 0.758

Mazda Rx-7 84-85 13B (Type M) Gearbox
1st: 3.622
2nd: 2.186
3rd: 1.419
4th: 1.00
5th: 0.807

Mazda Rx-7 86 13B 6PI (Type M) Gearbox
1st: 3.475
2nd: 2.002
3rd: 1.366
4th: 1.00
5th: 0.711 (0.758 UK)

Mazda Rx-7 87-88 13B 6PI (Type M) Gearbox
1st: 3.475
2nd: 2.002
3rd: 1.366
4th: 1.00
5th: 0.697 (0.758 UK)

Mazda Rx-7 87-88 13B Turbo (Type R) Gearbox (also the 929)
1st: 3.458
2nd: 2.015
3rd: 1.391
4th: 1.00
5th: 0.762 (0.806 Japan)

Mazda Rx-7 89-92 13B 6PI w/o LSD Gearbox
1st: 3.475
2nd: 2.002
3rd: 1.366
4th: 1.00
5th: 0.697

Mazda Rx-7 89-92 13B 6PI with LSD Gearbox
1st: 3.475
2nd: 2.002
3rd: 1.366
4th: 1.00
5th: 0.756

Mazda Rx-7 89-92 13B Turbo Gearbox
1st: 3.483
2nd: 2.015
3rd: 1.391
4th: 1.00
5th: 0.719

Eunos Cosmo 90-95 20B-REW JATCO Automatic
1st: 2.78
2nd: 1.54
3rd: 1.00
4th: 0.69

Eunos Cosmo 90-95 13B-REW JATCO Automatic
1st: 3.03
2nd: 1.62
3rd: 1.00
4th: 0.69

Mazda Rx-7 93-95 13B-REW Gearbox
1st: 3.483
2nd: 2.015
3rd: 1.391
4th: 1.00
5th: 0.719 (0.806 Japan)

Mazda Rx-8 04-current 13B Renesis Gearbox (manual)
1st: 3.815
2nd: 2.260
3rd: 1.536
4th: 1.177
5th: 1.00
6th: 0.787

Mazda Rx-8 04-current 13B Renesis Gearbox (automatic)
1st: 3.538
2nd: 2.060
3rd: 1.404
4th: 1.000
5th: 0.713
6th: 0.582



Differential Gear Ratios

Q. Are the turbo stub shafts interchangeable?
A. Somewhat.

• 89-92 have a longer right side and a short left side.
• There is a vin split for the 86-88 shafts.. 608385+ are different the ones below that vin.

Q. I heard about the Kia Sportage and Mazda truck differentials, what are the facts about this?
A. I am going to break this up into two parts.

1. The Kia Sportage

• Available in the pre-2002 Kia Sportage. 1997 may not have the 4.78, but i have not been able to confirm this. Also, there may be another ratio other than the 4.78, but again, i have not come across them.
• The 3rd member is a direct bolt in to the 84-85 Rx7 axle housing.
• It is an open differential. But a LSD unit meant for an 84-85 rx7 will work fine in it.
• The holes on the kia member are larger than the Rx7 member, but it is not an issue.

2. The B2600

• Come from the 1987-1988 4x4 5spd models. (front differential).
• Gear is a 4.44 with an open differential.
• Check for wear since these are older sets and usually not well maintained.

Mazda 79-82 12A: 3.909
Mazda 83-84 12A: 3.933
Mazda 84-85 13B: 4.076
Mazda 85 12A: 3.909
Mazda 86-92 13B 6PI / Turbo 5 speed: 4.10 UK models 4.30
Mazda 1988 Convertible: 3.91
Mazda 1989+ Convertible: 4.10
Mazda 86-92 13B 6PI Automatic: 3.91
Mazda 1989 GTUs 5 speed: 4.30
Mazda 93-95 13B-REW Manual: 4.10
Mazda 93-95 13B-REW Automatic: 3.91
Mazda 09-current 13B Renesis Manual: 4.777
Mazda 09-current 13B Renesis Automatic: 4.3
Mazda 04-08 13B Renesis Manual: 4.44
Mazda Miata 5 speed: 4.10 or 4.30

Kia Sportage 98-02 4x4 (front diff): 4.78
Mazda B2600 87-88 4x4 5spd (front diff): 4.44
Mazda B2600 87-88 4x4 Auto (front diff): 4.10

^^all of the above will direct bolt into the Mazda rear end. All are large spline differentials.

You can use an rx7 pinion seal in a kia sportage third member, its a little different design, but it will fit and so far has worked for me. I will update if any issues arise.

Availible Aftermarket Gears
see Mazdatrix.com for details

1979-1985
4.444 27-110A-M054
4.875 27-110A-1312
5.125 27-1100-1480

1986-1992
86-92 3.91 Non-turbo No Longer Available
86-92 4.30 Non-turbo 27-110A-M066
*86-92 4.875 Non-turbo 27-1100-487C
86-92 4.30 Turbo 27-110B-P092

Also
5.12 and 4.77 Rings and Pinion Sets now available for 86-92 Turbo FC's!!
These are made from the RX8 ring and pinion sets, using your used FC Turbo pinion gear (you must send it in before we can start - we have no cores).

Special order -- takes about four weeks.

Supplied with special rear pinion bearing and special spacer.
Must use the 93-on sleeve #27-171A-R004 (not included with ring and pinion)
5.12 is #27-11FC-5120-TB
4.77 is #27-11FC-4770-TB

1993-1995
3.909 27-110A-P062
4.10 No Longer Avalilble
4.30 27-110A-P0A5
4.44 27-110A-PA28
4.77 27-110A-RS08
5.12 27-110Y-PA28-05

Notes:

• 93-95 pinion is shorter than the 86-92
• Short pinion on Rx2, Rx3SP and 79-85 Rx7
• Long pinion on Rx3

Input Shaft Information

Turbo: 1"x23 Spline (same as some Ford applications)
NA: 1"x22 Spline