"95 Olds 88. Vibrations starts around 55 and goes away around 85mph. New: front ball joints, rack, tie rod ends, front/rear struts. Thought the install of Chrysler Concorde wheels was the problem (wrong bolt pattern size) Bought new wheels, same problem. Discount Tire said the Goodyear Vivas were the problem, bought new Reiken Raptors (225/60-16). Same problem. Took it to a shop that balances wheels on the car. They said they found a couple out of balance and fixed it along with an alignment. Recent 2500 mile road trip proved the problem is still not fixed. Engine RPM has no effect on vibration change. Shifting to neutral during the vibration range has no effect, same with running the car up to speed using different gear selection. I have checked everything I can think of. Drive shafts are tight, wheel bearings front and rear, tight. Control arm bushings good. Anything below these speeds is good. 85 to speeds I won't admit to is good. The only things I have not replaced are the drums and rotors but the on-car balance indicated these were ok. I am totally frustrated. This is my road car and the constant vibration is driving me nuts. I would hate to park it on road trips and use the Mazada!!!

How are the wheel hubs?

Hubs/bearings tight. Just returned from a rebalance from Discount, no change. Axle shafts? No play that I can find but they look OEM and the car 190k on it. Vibration is coming from the front. If I didn't value my hair so much, I would be pulling it out.

look for loose body panels or hood misalignment i don't know if that is a problem with bonnies but it was on the gallant i used to own

Not to imply that you didn't do it right, but how did you test to make sure that the hubs/bearings are still good?

Obviously since it starts at 55 and ends at 85, it has something to do with something that rotates.

What do you mean by an on-car balance? Were those wheels actually taken off the car to be balanced? I had this exact same symptom with my car, and it turns out that the first shop didn't balance the wheels properly, so I took it to another shop and they did it the right way.

Wheels were balanced off the car at Discount. Last shop balanced them on the car. In checking the bearings, I pulled all the wheels off to check for play or rough feel. One had slight play and it was replaced. In checking around with different sources, I am leaning toward the driveshafts (with 190k on them) being worn though they did not exibit any looseness, no clicking on turns ect. Pricing for remans is within my budget so it couldn't hurt to replace them since I have put this much time and money in it. The problem has stayed despite different wheels and tires.

Generally, wheel hubs are tested with the wheels **on**. That way, you have more leverage to wobble it around. I say jack up the car and test the front wheel hubs again. I highly doubt your drive shafts will be causing that much vibration.

Is it in the steering wheel? If so, does it shake up and down or shimmy left and right?

If I read it correctly, it seems you have replaced everything possible except your rotors?

Correct, everything except rotors and drive shafts have been replaced. With the on the car wheel balance, I would think I could discount the rotors as being the culprit. The concise alignment the shp did reveled no worn suspension components. The drive shafts are OEM with 190k on them, Boots are intact and no clicking noises on full lock turns. The vibration seems to start on the left side and works it way thru the steering wheel. I have gone as far as swapping back to the OEM wheels and tires with no change. The $$ involved with replacing the drive shafts is not an issue and with the miles on the car, replacement seems justified. Now, I just found out a dear friend passed away yesterday and an unplanned 2k road trip is looming for the end of the week and I would like to figure this vibration issue out. I have read some horror stories about replacing the shafts so any information on what to watch out for would be appreciated as this project time line has been moved up to a gotta do some thing now project.
I bought this car as the second owner and it has proven to be a friend and an enemy, depending on what failure has occured. Thru the help of this forum, it has become a very depenable rig and my primary "road rig" At this point, the vibration is the only issue left to cure.