bryanska

My 2007 AT Fit has been making a whining/whistling noise upon acceleration before upshifts.

- It happens when I apply “medium” throttle or above
- It’s random and NOT ALWAYS before every upshift, but usually happens before an upshift and dies off once in a higher gear
- The noise sounds like air, or a supercharger, but may be bearing noise
- Usually once per acceleration instance (i.e., only one instance of the noise until I hit cruising speed)
- Seems to be coming from passenger side front
- Only happens when moving, not when stationary and revving the engine
- I recently drained and filled the AT fluid
- I also replaced the inline trans filter under the battery
- Recently changed the serp belt and idler pulley, as well as the engine air filter
- I also get a crunch sometimes when shifting into first from a stop, not sure if this is a trans or axle issue

I’ve already tried revving the car while stationary, and holding a mechanic’s stethoscope to the alternator, idler, and AC unit. I’ve done this to 3000 RPM with the AC on and off. The noise did not occur.

The trans fluid still looks great about 8k after being changed, and is at the correct level.

The car does not shift hard or delay shifts. I assume all Fits are a bit jerky and loud anyway. It never shifted as smoothly as a GM auto, for instance.

The noise is VERY slowly getting worse. Say, over about 3000 miles I’ve noticed it more and more.

Any thoughts?

It is possible the serp belt change is causing the noise. But then again, the transmission is an equally likely culprit, as is the inline filter. I am not sure where to start.

Nitrous1024

It sounds as though the "start clutch" on your transmission is going bad although you aren't using a CVT nor did you mention doing anything with the clutch so I assume you have a normal automatic transmission.

Post the transmission code for us to provide better suggestions