Hello all... Man, I sure have bee posting a lot this week. Ok. I am beginning to notice a faint but high pitched squeal or whistling noise when cruising at 40. If I rev the engine, it goes away but quickly returns when the motor returns to cruising speed. From what I can tell thus far, it isn't too loud, but I would like to figure out what it is... Any Advice is appreciated.

If you rev the engine it goes away... sounds like it's Drive belts , not the Center bearing on the driveshaft.

Can you get it to squeal in Neutral, standing still?

If you can, get a spray bottle and spray water on each fan belt to see which one is the culprit.
Many times, the alternator pulley is skewed a bit so the alignment between Alternator and Crank pulley is off. Even with new Alternator bracket bushings, I still have to hold the alternator as I tighten the Pivot Bolt... just using the tensioner is guarenteed to cause the alternator to skew
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'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me http://home.lyse.net/brox/TonyPage4.html http://cleanflametrap.com/tony/

Another source of the whistle might be the intake manifold gasket, Mine did this but did it at idle also.

No, no whistling at idle... from what I can tell, it is limited to that speed... I can't hear it at highway speeds, but there isn't anything for the sound to echo from on the highway
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1989 244 DL first Volvo

spray some lubricant on the center driveshaft bearing - I suspect the whistle will go away - if it does I'd order a new one and replace it along with the rubber bushing that holds it in place,-- but some will tell you that you can just lube it up periodically.

Damn! It seems everything Rubber on my car is failing at the same exact time! I replaced the motor mounts 2 months ago, the trans mount this weekend, need to replace my TAB's, and if this is it, I am curious as to how much I am looking... Dangit... Does the list of parts never end? Thanks.. sorry,,, small rant there.

Your car is 22 years old. Expect just about any thing rubber that has not been replaced to fail over the next 12 months.

Of course the center bearing is not rubber...

I just lubed my carrier bearing over the weekend, very easy job.

Get a needle/zerk attachment to go on the end of your grease gun.

Slide the need between the plastic cover on the bearing and shoot
the grease into it while spinning.

You can also drop the drive shaft and do it, also not hard, just make
sure to put the drive shaft back in phase. Check your black doughnut for cracking and such.

What kind of grease/lubricant should be used?

I know the driveshaft bearing isn't rubber but you mentioned another bushing...
What is the easiest way to drop the driveshaft?

There is a metal support/carrier in the center of the driveshaft. I think there are a couple of small bolts that hold it to the frame - not sure, check it out. If you drop it you'll have better access to the bearing and the rubber support. Mark its spot so you can put it back correctly.