Is this an automatic or manual transmission? I have never had very good luck identifying a noisy bearing by holding it and playing with it so disassembling the transmission to inspect it is relatively ineffective. A noisy bearing could very easily be overlooked so it's best to just replace them.
There aren't many ball or roller bearings in an automatic transmission. It's mostly sleeves with oil in between similar to engine crankshaft bearings. Those don't make whining noises. If the fluid level is low, air can get sucked up. THAT will make a whining noise.
The best way to identify the cause is to listen to it while it's under load and the conditions are met necessary to make the noise occur. A dandy tool for that is called the "Chassis Ear". That is a set of six microphones, a switch box, and head phones. You clip the microphones to suspect points, then switch between them while listening during a test drive. Be aware that many mechanics have never seen or even heard of this tool but it's used by suspension and alignment mechanics to find clunks and rattles. Auto parts stores that rent or borrow tools may have it. I recently found out you can find it on Amazon. Com for one third of the normal price.
Tuesday, May 15th, 2012 AT 9:47 PM