← Mazda Miata NB (1999-2005 US model years)
Will NB 6-speed manual transmission (with NB shifter) fit a Mazda Miata NB (1999-2005 US model years)?
Short answer: Yes. Confirmed
Yes: Sources agree the 6-speed bolts into a 5-speed NB.
| Part | NB 6-speed manual transmission (with NB shifter) |
|---|---|
| Vehicle | Mazda Miata NB (1999-2005 US model years) |
| Years | 1999-2005 |
| Trim / condition | manual NB; bring the shifter from the donor car |
| Verdict | Reported to fit |
| Confidence | 3 of 3 — Backed by a manufacturer document, or two or more independent sources agree on a specific checkable fact. |
| Last verified | 2026-10-20 (date the cited sources were last read) |
Details
Sources agree the 6-speed bolts into a 5-speed NB. A forum poster found the NB 5-speed and 6-speed transmission plates identical and the starter used all three bolts (the two-bolt starter issue applies to NA cars). Use the shifter from the same car: one dealer says only early-2001 6-speed shifters match the NB1 unit; mid-2001-on cars use a larger shifter. Reverse/neutral switch wiring may need attention on swaps. Match the rear ratio (6-speed cars used 3.909, 2004-05 cars 4.10).
Specs
- ratios: 3.76/2.269/1.645/1.257/1.00/0.843
- note: US 6-speed paired with 3.909 rear
Related build entries
Other drivetrain fitment for the NB
- 2004-05 Mazdaspeed Miata Torsen differential with MSM axles — Fits with extra parts or work
- 1994-2005 differential, driveshaft and axles (7-inch rear) — Reported to fit
This part on other generations
- Mazda Miata NA (1990-1997) — Fits with extra parts or work
Sources
- NB Miata Compatibility Guide (NB2 to NB1) — Redline Auto Parts (used-parts dealer; hands-on checks, own disclaimer; Dec 2018) (vendor article; read 2026-10-20; full page read)
- Help me guys with 6 speed swap — Miata Turbo Forum (forum thread; read 2026-10-20; search excerpt only)
- 5-Speed vs 6-Speed NA/NB Miata Transmission — MiataSource (parts vendor blog) (vendor article; read 2026-10-20; search excerpt only)
Summaries are in our own words. Fitment is not guaranteed — disclaimer.
Report a correction — spotted an error or have a better source? Email hello@chassisdex.com.