I had a similar problem and it was because I had a nasty bubble in my front tire. Might want to check that. The symptoms were exactly the same, car shaking when driving above 20mph, steering wheel shaking, etc.

 

I would assume that with a bubble in the tire or bent rims, it would shake at all speeds under any throttle position. Mine only shakes under acceleration in the upper gears. I think the rotors may be catching the pad, as I was turning the wheel yesterday when I replaced the axle and it would stick because they are so warped. That would cause shaking while at any speed, I would imagine. I guess I will check the DS axle this weekend because I noticed a little shake when it was first installed but it went away after a while. Is there any chance it could be a broken/cracked motor mount?

 

It could be a motor mount for sure.

 

OK. I will check because it seems kind of strange that it shakes only in those gears and only while accelerating. The new rotors will help with the shaking while braking but during acceleration, I have no idea except motor mount. How would one go about fixing one of those if it did happen to be the culprit?

 

You could buy some used mounts that weren't torn, or buy some mount inserts.

 

So, I checked my motor mounts when I replaced my rings and they were fine and I replaced all four rotors this week and it still shakes. My girlfriend thinks that it may be the fuel filter since it only shakes while accelerating from 40-80 mph. I am don't really believe it has anything to do with the fueling but rather the chassis or drivetrain. Is there any reason to be believe that what she is suggesting is true? Let me know, because I am on the brink of having a mechanic diagnose it so I can fix it.

 

Is it only under acceleration, or does it do it while coasting or in neutral?

 

It is only under acceleration between the speeds of around 40 mph to about 70-80 mph. After that it stops shaking. I am going to get my tires balanced and aligned this weekend as this is the last thing I can do before just giving in to the outside help of a mechanic.

 

So I replaced my fuel filter but I still have the same problem. So I can rule out fuel as a culprit for the shaking. The last step I do before I take it to a mechanic is balance the tires and get an alignment. If that doesn't fix it, the problem is out of my hands.

 

Possibilities I can think of are this:
1.Tires/rims/alignment
2.motor mounts-Did you tourque them real well with a wrench
3.let's hope it's not internal