So yesterday I took the Thunderbird out for a drive after it sat all winter. Everything was fine. After the car warmed up I did some wot runs. There was a weird squeal and vibration I could slightly feel in the floor from 4000-4200rpm. Above or below that range there was no noise/vibration. I went home and could duplicate the condition with the car in park. So to narrow the issue down I removed the accessory belt and started the engine. I revved the engine up to the same speed (4000-4200rpm) and the squeal/vibration was gone. That ruled out the damper, crank, and torque converter and isolated the issue to the front accessories. The water pump pulley, smog pump eliminator pulley, A/C compressor pulley, and power steering pump pulley spun straight and true by hand. The alternator pulley, however, wobbled slightly when spun by hand. I put the belt back on and the squeal/vibration was back. I listened to the alternator with a stethoscope and, when the engine was revved up, the alternator clearly made a noise I could hear through the stethoscope.
So based on the process of elimination I'm fairly certain the alternator is the culprit here. Has anyone has a bad alternator shaft/bearing resonate through the car at high RPM? The alternator has a lifetime warranty so it will cost me nothing to swap out.
I've seen bent shafts.... Had one on the Lincoln.
What Paul said...I had a bent shaft on my '92 F150's alt...
I'll be swapping out the alternator as the 3G unit I bought has a lifetime warranty. So it's a free swap. I'm just surprised it died in only 2 years. The belt is not too tight or anything.
After your alternator swap-out I highly recommend replacing the serpentine belt with a Goodyear Gatorback (Note: Continental took over production and renamed it the Elite Poly-V Belt with Quiet Channel Technology.) I was chasing a belt squeal for over a year before I discovered the high grip Gatorback. New belts were quiet for about two weeks before the squeal/chirp returned. Drove me crazy. The Gatorback has been on for the last six months with no chirp or squeal.
It really shouldn't squeal no matter what unless somethings messed up. I run cheapie belts and have no squeal.
I was in love with my 3g upgrade. But after doing it, meh. Not really that much difference. I felt like it was a worthy upgrade on my cougar, but driving the tbird I don't miss it.
Turns out the 29 year old belt tensioner is ping out. When the bearing squeals there is no vibration. When it doesn't squeal there is a vibration. I guess after 29 years and 135K miles it's time for a new one.