"Fluttering" Under Load
 

Well maintained 1987 NA with 165K miles: While driving under some load...like a medium uphill grade in 5th gear with engine at around 3K rpm's - I can feel a slight "fluttering," like something is just a bit out of balance.

Hard to say exactly where this is coming from - but definitely not from the rear of the car. More like either directly underneath the gearshift, or forward towards the back of the engine.

Balance shaft timing checks out ok - so my thought is that this is a torque-tube issue. As in it may be time to address the TT bearings. Then again - perhaps this an early sign of a main bearing issue?

Oil pressure has always been good. All other gauge readings fine and consistent.

Any ideas? Thanks!

Can you do a better job of expressing the fluttering? Is the steering wheel moving, is the shifter moving (or can you feel it with your hand on the shifter?) Is it an acoustical buffeting feeling/sound? And can you guess as to the frequency. Or can you record it and post a file here?

I'm a former product developer and this is interesting to me and unusual enough that I bet we can figure this out.

Doug

No movement of shifter or steering wheel. No metal on metal, but much softer. Acoustical buffeting feeling/sound is more or less accurate, but very faint (not loud enough to record), and at a frequency which equals rpm's. Sounds a bit like the flutter of the humming birds that show up at our feeder.

And its only under moderate load at that speed (3k in 5th must be like 70?)? If it can also be reproduced in other gears at same RPM and lower vehicle speeds, say so. I'm assuming this is the ONLY speed/load condition that causes it unless you say differently.

Do you have your engine bay engine pan on? If you raise your headlights when its happening, does anything change? If you let off the gas does the instant drop in torque instantly stop it, or does it get less intense? What if you put your dash fan on high - any change?

Biggie is my question on whether you can get it do do this in other gears.

Could be torque-tube bearings.
Or rod-bearings.