i have a 96 Bonneville SE, 178K miles. my engine has recently acquired a shaking at about 2.4 RPMs on the highway. only does it when its trying to accelerate, most frequently at about 75 mph. its an engine shake, not a body shake. my brother thought it was the transmission, but when i took it in, i had them check out the transmission, service it, and pour in a bottle of Trans-Ex. didnt solve the problem, even for a short period of time. now my brother thinks its the front driver side wheel [he thinks its a bit loose], but my steering doesnt cause it or cause it to stop. it seems to have no bearing on the problem [forgive the pun]. any ideas?

Now if you speed up to say... 80 then hold it does it rattle..? or does it rattle when you decel from that speed?

Do the RPMs move when it shakes?

it doesnt rattle if i speed up, if i take a more active role and adjust the gas any [it usually happens when on cruise, but not always] the shaking stops. it does, on occasion, shake when i slow down from highway speeds to make an off-ramp [though it hasnt lately, its very rare]. the RPMs do not move at all while its busy shaking. almost like its stuck there, if i adjust the gas, like i said, and make the RPMs move, the shaking stops.

Sounds like it might be a harmonic balancer, which is usually needed to be replaced on higher mileage 3800'*. My other thought is something up with the crankshaft, but let'* hope not.

Have you tuned it up recently... Spark plugs, check the wires, fuel filter, air filter, etc?

its been a couple months, but i got it tuned up after this started, and it didnt affect it any.

Check out this new thread. He describes what his car was doing and how he replaced it. This is just an idea, not saying that your car is doing this. Check it out:

http://www.bonnevilleclub.com/forum/...pic.php?t=6749

im taking my car in for an oil change next week or so. yes, i know i should change it myself, and i would save for the fact i dont have any of the stuff i need to do that. so lets dismiss that. im also getting my tired rotated, im going to have them check the harmonic balancer and the bearings. oh, and im going to get them to fix the leak in my ac [theres no doubt theres a leak, i was bone dry on freion last time, and ive got a suspicion im dry again, a mere two months later]. if its not the balancer, any ideas what else it could be? the rattlings becoming more pronounced now, not just limiting itself to speeding up at highway speeds or slowing down on off-ramps.

so i took it in awhile ago, finally decided to get back with u guys. guess what it was. no, go ahead. guess. i said guess! okay, seriously, my rotors were warped. thought id let u know, i know how u were dyin to know