Front wheel hop (maybe) when I lift off accelerator.

Still cannot find what is going on. I have replaced the tires, balanced them twice, replaced front struts, replaced bushings and ball joints on lower control arms, replaced outer tie rod ends, replaced cv joints and half shafts (both sides), and replaced hubs and bearings.

This was all done trying to stop what initially felt like a tire out of balance while driving around 50 to 55 mph.

Having done all of this "fixing", I was driving the car at around 40 MPH on a very smooth (newly paved) road; when I lifted off the accelearator, the front end began shaking again. Still feeling very much like a wheel out of balance might.

I am totally at a loss as to what to suspect next.

The engine in the car has about 500 miles on it after a total rebuild, and the transmission has about 25,000 miles on it also after a total rebuild.

What I am feeling, I am almost positive appears to be something that spins and is out of balance, shaking the front end of the car. My next thoughts would be possibly an unbalanced flywheel or maybe something is going on with the torque converter. I am only speculating at this point as they are the only things I can think of that spin and need to be perfectly balanced.

Does anyone wish to put their two cents worth of "maybes" in the discussion? I am just about ready to just give up! You can't imagine how frustrating this has been.

Thanks to any of you fellow Riviera lovers for any ideas you might have.

I started this new thread because the original one has pretty much changed course since I started it last year!

The next time you're driving at that speed, induce the vibration, and put the trans in Neutral. I'm just curious if the problem goes away. Or, put the gear selector into 3rd and see if it goes away while remaining at the same speed.

Is this a "hard" vibration? Meaning could it possibly feel like a misfire or a fish biting your lure? Or is it just a continuous vibration?
I know, weird questions, but I'm trying to go somewhere with this....

S/C 95 Rivs came with 2 different flywheels. Not sure how to tell which one goes with which motor. One has a weight attached, the other does not. When I put the new tranny in my car, we used the wrong flywheel and the vibration increased with RPM.

Could be the brake rotors, I didn't see you say anything about replacing them...

i have same prob with me 95 at about 65 it gets a shimmy and just driving around town the steering wheel kida wobbles so I ordered a cv shaft for the passenger side cus it felt as if it had alot of play to it compaired to the drivers side cv shaft but they sent me the wrong shaft so Im waiting on it. But when I had it apart I notice that the holes in the brake rotors were larger by about a 1/16th of an inch compaired to the wheels studs and I got to thinking mayb its got the wrong brake rotors on it cus they should fit snug around the wheel studs like most do, I haft to take it apart again to confirm the hub centers up the rotor when u tighten the lugnuts. All the bushings in the front end on my car are good and solid and iv been chaseing this shimmy for awhile now. like most I had the tires replaced and rebalanced and all that and didnt help.

sloshua wrote:

i have same prob with me 95 at about 65 it gets a shimmy and just driving around town the steering wheel kida wobbles so I ordered a cv shaft for the passenger side cus it felt as if it had alot of play to it compaired to the drivers side cv shaft but they sent me the wrong shaft so Im waiting on it. But when I had it apart I notice that the holes in the brake rotors were larger by about a 1/16th of an inch compaired to the wheels studs and I got to thinking mayb its got the wrong brake rotors on it cus they should fit snug around the wheel studs like most do, I haft to take it apart again to confirm the hub centers up the rotor when u tighten the lugnuts. All the bushings in the front end on my car are good and solid and iv been chaseing this shimmy for awhile now. like most I had the tires replaced and rebalanced and all that and didnt help.

The brake rotors fit like that on our cars, and most cars for that matter. As long as it's snug around the center ring of the hub, it's fine.

+1 on the gap around the studs. Like Abaddon said, as long as the center bore doesn't have a gap you're fine. The only car I've seen that didn't have the gap around the studs is our 68 Camaro, and that's because the studs are part of the rotor.

I will try the shifting of gears next time I drive the car and get back to you with results. As for rotors, they are brand new. The rotors, calipers, pads and brake lines were all replaced before I started on the suspension. Also new shocks (rear) and front struts.

Thanks for the input.

designer1962 wrote:

Still cannot find what is going on. I have replaced the tires, balanced them twice, replaced front struts, replaced bushings and ball joints on lower control arms, replaced outer tie rod ends, replaced cv joints and half shafts (both sides), and replaced hubs and bearings.

This was all done trying to stop what initially felt like a tire out of balance while driving around 50 to 55 mph.

Having done all of this "fixing", I was driving the car at around 40 MPH on a very smooth (newly paved) road; when I lifted off the accelearator, the front end began shaking again. Still feeling very much like a wheel out of balance might.

I am totally at a loss as to what to suspect next.

The engine in the car has about 500 miles on it after a total rebuild, and the transmission has about 25,000 miles on it also after a total rebuild.

What I am feeling, I am almost positive appears to be something that spins and is out of balance, shaking the front end of the car. My next thoughts would be possibly an unbalanced flywheel or maybe something is going on with the torque converter. I am only speculating at this point as they are the only things I can think of that spin and need to be perfectly balanced.

Does anyone wish to put their two cents worth of "maybes" in the discussion? I am just about ready to just give up! You can't imagine how frustrating this has been.

Thanks to any of you fellow Riviera lovers for any ideas you might have.

I started this new thread because the original one has pretty much changed course since I started it last year!

How about the engine and transmission mounts? Ever take a good look at all of them?

I just drove the car to the grocery store and got it to do its "shimmy" a bit. I shifted it into neutral and the shake seemed to stop. It resumed when I put it back into drive. Didn't get a chance to try in 3rd yet.

As for motor mounts the rear one by the firewall was switched when the engine went in.

That one at the front would definitely be worth checking out. The side mounts that connect to the unibody kinda just hold the motor in orientation. That back one you changed already and the front one really take all the torque I think.

turtleman wrote:

That one at the front would definitely be worth checking out. The side mounts that connect to the unibody kinda just hold the motor in orientation. That back one you changed already and the front one really take all the torque I think.

+1.

Agree here - I don't see engine/transmission mounts on your list of parts. If the engine/trans moves significantly on decel, you will put stress on the CV joints and get a vibration. Shifting to neutral makes it go away... because you are taking the load away from the mounts and the transmission goes back where it belongs.

Note to sloshua - you are talking about a completely different issue than the OP - his problem is on decel. Not that it isn't necessarily the same solution (mounts?), but it's confusing to add here.

replaced the cv shaft on the passenger side today got rid of most of the shimmy! Sry I didnt mean to butt in
those shafts are heavy should at least check for play on them theres so many ways them damn things can go out of wack