Whining/Whistling before upshifts – mystery, need help
 

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.

Update - it may be the AC. I drove around today specifically with the purpose of tracking this damn noise down. The AC button may help... i will keep the group updated.

I have heard automatic transmission equipped cars doing what you describe.. It has been a long time back and the years may have messed up my memory but I believe it was noise from a bad torque converter.

Check and change the trans fluid. My car is making some noise too but not sure if its the trans. I need to change mine too.

This is an old thread, but did you figure it out?

Sorry such a late reply!!

It was the AC compressor. When I listened to the car with the stethoscope, I didn't rev it up enough times for the noise to happen. The random occurance of the noise meant that I never heard it when the car was on jackstands...

One afternoon I said "F this, I'm gonna figure it out" and made a matrix of variables. One after another, I crossed them out. Then I ran with the windows open and AC on, and drove up and down a street next to a high wall.

Sure enough, whenever the AC compressor kicks on simultaneously with acceleration, a whistling/whoosing noise is heard. If I turn off the AC in the middle of the noise, it goes away immediately. Like switching off a light.

I don't know if it's a bearing in the compressor, or a normal noise. Any thoughts are appreciated.

Kinda sounds like a supercharger?

The A/C compressor on my GE does that under partial throttle (makes sense because the compressor is turned off under full throttle to free up power).

I just ignore it, it's done that since new. I only use A/C if I have passengers though so it doesn't bother me much.