Answer
Dec 07, 2025 - 10:38 PM
Sounds like you’ve got a pretty classic Miata problem there. If the car will move perfectly fine in reverse but not in any forward gear, here are the usual suspects:
- Clutch is slipping like crazy — Reverse has a different gear ratio and loads the clutch less, so a totally worn-out clutch can sometimes still move the car backward but not forward. If the engine revs but the car barely crawls forward, this is your top suspect.
- Stripped or damaged input shaft / clutch hub — On old Miatas, the splines on the clutch disc or the input shaft can get chewed up. Reverse may still grab because of gear design, but the forward gears can’t transmit power.
- Transmission internal gear failure — Not super common, but if a forward gear set or shift fork is damaged, you may “feel” like it’s in gear but nothing actually engages.
- Driveshaft / differential issues — Less likely, because reverse works, but:
- broken spider gears
- ring gear issues
- driveshaft splines But usually those fail in both directions.
- Shifter/linkage not fully engaging the forward gears — The Miata shifter bushings wear out and the linkage gets sloppy. Sometimes it “feels” like it’s in gear but it’s barely engaging.
If I had to guess without seeing it: 👉 Clutch is probably toast. Old NA Miatas do this when the clutch disc is worn to the rivets.
But to be completely sure, it's best to get the service manual. This 👉🏻 1990 Mazda MX-5 Miata OEM Service & Repair Manual, in particular, can help you if you want a proper step-by-step on checking clutch travel, flywheel condition, or gearbox inspection. It walks through the whole drivetrain pretty cleanly.
