i have a 1990 toyota 4runner. when i push in my clutch to shift gears i hear a strange and slight whistle noise. 98% of the time it only happens going from gear to gear. if i put it in neutral and just push the clutch in and out it doesn't do it. it seems like air is being let out somewhere and is causing it to whistle. but only when shifting gears.

vacume leak? thats the only thing i can come up with. but i wouldn't know where to start.
any ideas?

 

Sounds maybe like a synchronizer or two is going bad; have you checked your tranmission fluid level?

 

Mass Air Flow sensor on mine (3vze) whistles when I put the clutch in to shift. It's always done that since I've owned it. It seems to be in proper working order, and I think it sounds kinda cool.

When you shift between gears, at speed, the engine tends to rev up slighty as the clutch releases the flywheel. This causes an increase in air flow through the air filter box past the MAF. I notice the same noise when I accelerate and simply depress the clutch, without shifting. And at times when downshifting suddenly, too.

 

Pilot bearing? I know this is more of a chirping but maybe that's what you meant

 

that sounds like a pilot bearing to me too homie. if that is the case it should only do it at a standstill in gear with your foot on the clutch.

 

that sounds like you are describing it to the T. i can rev the engine in neutral and push the clutch and it will makes the whistle. that makes sense that it would do that. does it really cause a problem? it doesnt really drive bad or anything when it does it. just kind of annoying.