When im cruzing between 40-50 mph, the car makes a humming/whining noise and i have no idea what it is or where it is coming from. It will stop if i take my foot off the gas, but as soon as i press the pedal, there it is again. It only does it at these speeds, no other time. The car is a 91' Z28 305 TPI auto, any help is appreciated.

 

If you are in park and you rev the motor does it still do it?

 

Nope not one bit.

 

Does it go away if you step into it, and the tranny kicks down for passing?

 

No it only does it if my foot is just slightly pressing the gas.

 

Rear wheel bearings? Pinion bearings? Just guessing, but it may help.

Mark.

 

Sounds like the tranny. Try going up a steep hill at that speed, and lightly press on the gas. I'd bet anything it will sit and shift back and forth between gears, and make a horrible racket. How many miles do you have on the car?

 

180k

 

If it is indeed the tranny, how bad of damage do you think there is?

 

bump

 

I have the same problem with the humming noise. It only does it when I I press the pedal even if it is lightly pressed. When I let go it stops the humming. Did anybody figure out what it was. My problem started when I switched out the rear end for a posi unit from a '94 z28 with 3.73 gears.

 

nope still havent fixed it yet. my car came with the stock posi 2.73 rear if that helps at all?

 

ATRATB256A JAN 96 A/T - 4L60/700R4 Rear Planet Failure/Lack Of Lube

ATRATB334 JAN 96 A/T - Delayed Forward Engagement/Burnt 3-4

932287A JUN 93 A/T - Click or Whine in Third or Fourth Gear

Found these on the preliminary search at Alldata.com, but I don't have a subscription.