I have been plagued with noise / vibration / harshness / resonance over the years that I swore I would tune out or sell the car out of defeat. Yes - I'm the guy that will cut perfectly good brand new mufflers back out of a vehicle and throw them in the scrap heap in an effort to find the "right" sound (maybe I'll actually get there someday??). Two issues I have been battling with have been a very high sensitivity to tire balance and also driveshaft harmonics (everybody has their own particular demons...)
I get into a late model car, then back into the ol' '86 G body and sit there at various speeds cussing the unwanted gyrations - the longer and farther I drive it, the more it pisses me off. Whaddaya expect out of an old car, right? It IS the 21st century, and I expect a smooth damn ride thank you very much LOL.
While not directly automotive, being an open thinker (?), I tried SSD hard drives in our computers an OH SNAP !!! While they are Waaaayyyyy more expensive, but Zoiks!!! these things actually really do kick it up a helluva notch despite conventional wisdoms... If you are on the fence, just do it!
Ok, so let's try a few other things that *might* work despite what my knee jerk response is (hate snake oil type stuff overall) (but there ARE people out there that don't believe in hydroboost either, and guess what...) -
sorry - had to get that in there.
I have been on the fence for YEARS regarding aluminum driveshafts, as I have blown up and wrecked just about everything a hot rodder can
Driveshaft failures REALLY SUCK as some of you that have experienced it can clearly attest to. I have rebalanced my stock steel 2.75 driveshaft (exact same as OE in the Buick Grand Nationals, but they only had a 3.42 gear versus my 442's 3.73 gear)(which changes driveshaft RPM's at speeds), upgraded to an aftermarket wizzbang 3" diameter steel shaft that was spec'd to within a postage stamp of perfection, and still found resonant frequencies at various speeds. I kept reading and reading about the issues on the good ol' net, finding that steel can in some cases amplify certain frequencies, while aluminum would actually dampen the same frequencies - hmmmm. Certain GM service bulletins spec'd swapping out the OE steel shafts for aluminum replacements under TSB guidelines - ok, you have my attention. I took the plunge for a 3.5" shaft package rated for 700+ horse, installed it and OMG - one big demon now exorcised out of my life! I have to say that I am in complete disbelief that it is like night and damn day - super thrilled! I know there are people out there that could argue steel versus aluminum for a driveshaft to the point of stupidity, but I will tell you that I am THRILLED. Higher numeric rear end gear ratios are even more of an issue than my 'lil 3.73 (especially with today's 6 speeds). Summary? I just cannot believe what an immense difference the installation of an aluminum driveshaft in place of previous steel shafts made in my particular world. Name your favorite brand of driveshaft supplier, though I do believe it is more the metalurgy that I am speaking of here. If you are on the fence, just do it!
Next ? Wheel balance... Oh my sensitivity seems to grow with every passing mile in my life! One HARSH beat session with my ride and the balance gets tossed out the window again - sheesh. Big smoky burnouts and harsh maneuvers shave rubber off unequally - I get it... But WTF !!! My next solution has been to try the tech that semi's have been using for years - beads inside of the tires!? I STILL can't quite wrap my mind around just how this exactly works, but man does it work! I put 4 ounces of the ceramic beads in each tire with no other changes (didn't remove the existing weights either) and WOW - highly impressed - smooth at all speeds at all times (unreal). Balancing that resets itself everytime you come to a stop and start rolling again? (Sounds like damn kitty litter in the tires when spun by hand up on the hoist) And can also compensate for minor imbalance in attached rotating mass such as rotors and brake drums? No way, right? I'm tellin' ya from my own experience, it IS true... If you are on the fence, just do it!
Some of you may not be advocates of the technologies mentioned above, but I am giving you my 2 cents in the one off chance that it may help someone here. Or course your mileage may vary, but it did the trick for me...