4kq -- thrum, thrum, every speed a thrum

[Robert Mangas]

    Tires.  Or at least, mostly.  I swapped to my summers and drove a couple 
hours.  No complaints at 40mph, and now that I'm back on snows, the thrum is 
clear at 40.  My summers are played out though, so it wasn't the cleanest 
test ;).

    New warm weather tires in the spring; then I'll know more :)

Thanks for the hep.


>From: Jpinkowish at aol.com
>To: porter_t_dog at hotmail.com
>Subject: Re: 4kq -- thrum, thrum, every speed a thrum
>Date: Thu, 17 Feb 2005 12:00:20 EST
>
>In a message dated 2/16/05 9:42:40 PM EST, porter_t_dog at hotmail.com writes:
>
> > Sound/vibe is speed related; can kind of feel it at lowlow speed but it
> >  starts to become obvious at 40mph.  Under load or coasting makes no
> >  difference.
> >
> >  Fresh tires are snows; Hakk 2's.
> >
> >  Did the thrum exist before.... that's a tough one.  I think so, but 
>it's
>SO
> >  different now (go figure!) that it's hard to sort before after.
> >
> >  Stock rims.   I'll swap them around tomorrow; they're always at 
>85lb-ft.
> >  Once the car is up I'll also check the tranny and diff fluid (hate to 
>miss
> >  something so obvious) and wiggle the propshaft.
> >
>Hi Robert,
>BTW, I'm interpreting a "thrum" to be a vibration with low-to-medium
>frequency, not a thump like a flat tire.
>
>If you are getting the "thrum" while coasting above 40mph, trans in 
>neutral,
>and the engine RPM is at idle, you can rule out the driveshaft center 
>bearing.
>  In this scenario, the DS isn't turning.
>
>You're running snows.  Boge TG are a firmer ride that stock.  That combined
>with the snows produces a little more hum.  These things do sing, and the 
>song
>changes with car speed.  Try your summah tiyahs.  Drive them for 10-20 
>miles
>and get them good and warm.
>
>No mention of replacing trans or engine mounts.  If the pass side engine
>mount is original, there's a good chance it's finished, fineto, at the end 
>of its
>life.  A dead mount does transmit some engine vibration to the front 
>subframe.
>   While coasting and trans in neutral, rev the engine.  Any change in 
>thrum?
>
>You didn't mention that you replaced the subframe bushings.
>
>Finally, has your exhaust system shifted so that it is just toughing the 
>rear
>diff?
>
>Finally, finally, all of your brake shields are on straight and not bent so
>they're touching something?
>
>Tell me this all solves the prollem!!  I'm dipping deep into the obscure!
>
>Jan