I just picked up a ’99 5-speed manual ZX2 with less than 60K miles for my son. While driving the car I noticed a growl in the drive train that changes with vehicle speed. Naturally, it’s the worst at highway speeds between 60 and 70 mph. I placed the car on jacks and had my wife run the car through the gears; the noise seems to be internal to the transmission rather than outboard in the half-shafts or rotor. I changed the transmission fluid so be safe but the noise is still present. Has anyone experienced this symptom?

You were right in changing the fluid. Deterioration or insufficent fluid will cause what you describe. If it does make more noise depending on how fast you are going in each gear the culprit is more than likely a worn bearing, shaft or gear surface. If it does it relative to the speed of the vehicle the culprit is a worn differential gear. If the noise in the differential gear is due to excessive backlash it can be adjusted.

Thanks for the reply. The noise does change with wheel speed so it sounds like a worn differential gear or backlash issue. My next question is do I need dive into the transmission right away or is this just a noisy annoyance?

It's not something you want to put off because if it goes out it will take the rest of the tranny with it. If just a whine you could drive it for a while. I've only heard of one other zx2 that had a whine and it was driven for a year before the owner put in a rebuilt.

Well Dave, here's the conclusion to the story: I jacked up the car and took off both front wheels. With my wife running the car through the gears I used a long screwdriver as a stethoscope and listened, again, to the transmission and wheel hubs. The left wheel hub had a sharper sound so I elected to try a hub bearing first. Thankfully this was the source of the growl. Bearing replacement was straight forward as long as you have a press available. **Note**I must caution anyone who trys this method of troubleshooting to use extreme caution as there high-speed moving parts that will happily grab clothing or tools as first chance.

Well, thanks for the moving parts warning. Not only can it grab clothing but the car will become a UFO if it falls off the jacks. Wheel bearing. Wouldn't you know.