When transmission is engaged...it's loud

My 90 CRX has been great to me and still is one of the most reliable vehicles I've ever owned, but I'm started to have concern for it. It just turned over 210,000 miles and the transmission is the original. When I push in the clutch the engine bay is quiet but when I let the clutch out even in neutral there's kind of a knocking whirling sound. At one time I changed the oil in it but I had to fill through the drain hole (long story) so I never have been sure of the oil level in it. Is it a bearing? The transmission still shifts fine and no problems with any grinding besides 3rd gear which only started grinding after I changed the oil in it :banghead: so what could it be?

Theres a bearing in your transmission, called the input shaft bearing aka clutch housing bearing. When your tranny is engaged and you hear whining noises, this bearing is to blame. However, if you have trouble DISengaging the clutch that would be your clutch throwout bearing. I am almost 99% sure that you have a bad input shaft bearing.
The tranny will need to come off and the casing needs to be opened to replace it. Heres a thread based entriely on this, it should help you:
http://www.honda-tech.com/zerothread?id=596873

acutally the first thing I would check is the pilot bearing. when you press in the clutch it will put pressure on this bearing causing it to quiet down.

mine does the same thing. but i have a no fluid in it for a on going 3 months. lol. still no horrible grinds. damn think wont hold fluid for crap. gonna reseal it when i take it out for the b20. ye ye

what'll happen if I do nothing and keep driving? Will the transmission possibly lock up and cause me to lose control or will it just break and roll to a stop? sounds bad either way..how much would a mechanic charge to diag/repair it.

edit: this seems like a stupid question but for my stupidity; is the bearing oiled by the tranmission oil and could a low oil condition in the tranmission cause this bearing to go bad?

Well I work at a shop and for us to diag anything we get a base pay of 1 hour labor to look at stuff, which is about 86 bucks.

If it is infact a input shalf bearing then yes low fluid could very easily have caused this problem to occur. It boggles my mind how you even "filled" it through the drain hole and got even close to the 2 1/2 quarts a honda takes on a spill and fill. What was the reason why you couldn't fill it through the fill hole anyway? If ithe head of the bolt stripped or just unable to come out with the tools you had, you could have just removed the gear driven VSS assembly from the top and the trans and filled it through there.

But the first place I would look would be the pilot bearing, because when it goes bad it will cause the symptoms you are experiencing. The trans has to come off no matter what and that will be the first thing you see. If anyone trys to tell you its a throw out bearing slap them in the face because cable trannys are not a constant riding bearing.