Vibration at 55-70MPH

[Tickle]

I have a 1996 convertible and I've been struggling to get rid of vibration that I am experiencing between 55 and 70 MPH. I initially thought it was cowl shake, but I'm not so sure anymore. The vibration is in the steering wheel and I can see my rear view shaking as well although I don't feel it in the seat--this leads me to believe its a front end problem. The vibration is there whether I am in gear or not.

So far I have tried:
-Full Length Subframe connectors installed
-All new tires
-Alignment x2
-Rotate and Balance x2
-New wheel and tire(Pass front--warped rim and bad tire)
-DS tie rod end replaced
-Front wheel hubs replaced

ETA:The PO installed Eibach Pro springs and CC plates.

I have no idea what it is and I could use some help or ideas of things to check. Its frustrating to have this thing vibrate at the speeds I drive the most. Please help!!!

Thanks...

 

[Zemedici]

driver wheel is alright?

 

[Tickle]

driver wheel is alright?

So I have been told.

I have been to the tire shop so many times I cant stand the thought of going back but I will have to. I'll have them check it.

 

[1997Cobra]

check your driveline. I had a little problem after my trans swap. A bad ujoint or something like that will cause all sorts of problems

 

[LilBerx]

If you have aftermarket gears I suggest going with an aluminum driveline. Cured my problem for my vibration that was 60+

 

[1997Cobra]

If you have aftermarket gears I suggest going with an aluminum driveline. Cured my problem for my vibration that was 60+

really? ive never heard that

 

[Blown_By_You]

I would check the driveshaft... and also put the car up on jackstands with the wheels on and run it up to speed in the air.. That's how I found out I had a bent axle, which I'm still trying to figure out how..

 

[Tickle]

So far I have these new things to check:
-DS Wheel/tire
-driveshaft
-ujoint
-axle(not sure how to safely check, no offense blown, but I can't drive it while on stands)

For those of you suggesting driveshaft or u joint, where should I feel the vibration? My experience tells me that a u joint vibration would be felt in the seat more than the wheel, is this correct?

Would a bad u joint vibrate only at certain speeds, or all the time?

How do I check the driveshaft/ujoint?

 

[CJK440]

-axle(not sure how to safely check, no offense blown, but I can't drive it while on stands)

Sure you can, you just won't be going anywhere.

You put the rear up on sturdy jack stands and "drive" the car up to the same speedometer speed that you noticed the vibe. This isolates just the rear driveline from the front wheels.

If when you do this you still notice the vibe, you can isolate further but pulling the wheels, running lug nuts on to hold the rotors in place and do the same test with no wheels on. This will let you zero in on the components in play.

 

[Blown_By_You]

Sure you can, you just won't be going anywhere.

You put the rear up on sturdy jack stands and "drive" the car up to the same speedometer speed that you noticed the vibe. This isolates just the rear driveline from the front wheels.

If when you do this you still notice the vibe, you can isolate further but pulling the wheels, running lug nuts on to hold the rotors in place and do the same test with no wheels on. This will let you zero in on the components in play.

Precisely how I found I had a bent axle. Nothing dangerous about it

 

[LilBerx]

So far I have these new things to check:
-DS Wheel/tire
-driveshaft
-ujoint
-axle(not sure how to safely check, no offense blown, but I can't drive it while on stands)

For those of you suggesting driveshaft or u joint, where should I feel the vibration? My experience tells me that a u joint vibration would be felt in the seat more than the wheel, is this correct?

Would a bad u joint vibrate only at certain speeds, or all the time?

How do I check the driveshaft/ujoint?

U joints on decel usually.

My car HORRIBLY vibrated above 80, when I was at the track and trapped 100, it was terrifying... I put an aluminum driveshaft in, and vibration is gone till about 120

 

[mysteed]

Sure you can, you just won't be going anywhere.

You put the rear up on sturdy jack stands and "drive" the car up to the same speedometer speed that you noticed the vibe. This isolates just the rear driveline from the front wheels.

If when you do this you still notice the vibe, you can isolate further but pulling the wheels, running lug nuts on to hold the rotors in place and do the same test with no wheels on. This will let you zero in on the components in play.

Precisely how I found I had a bent axle. Nothing dangerous about it

Same here.

 

[SVT CAMR]

Some things to check. Does it get worse when you turn the wheel left or right or does it go away when turning left or right? If so it is your wheels hubs bearings. Had this problem on my Escalade.

MPH related you will also want to check your drive shaft balance.

Did you replace the passanger side inner tie rod? Why not when you did the drivers side. Mat need to look at this as well.

Finally check all 4 tires.

 

[racecougar]

In addition to the things previously mentioned, have the wheels/tires been roadforce balanced or just spun-balanced?

 

[Fox 5.0]

Blown struts could be a cause of this as well correct?

 

[Tickle]

Just spun balanced.

 

[Tickle]

Figured I would update the thread. I had new stock motor mounts installed and it helped the problem a lot, there's still some vibration but not near as much.

Next I am installing new shocks and struts. Bit by bit I'm gonna get this thing to ride smooth.

 

[laddanator]

Figured I would update the thread. I had new stock motor mounts installed and it helped the problem a lot, there's still some vibration but not near as much.

Next I am installing new shocks and struts. Bit by bit I'm gonna get this thing to ride smooth.

Does this vibration occur if your are sitting still and in neutral and you rev the motor?

 

[Tickle]

None at idle in neutral

 

[ImThatGuy]

I would really check the u joints on the driveshaft and replace with FRPP aluminum driveshaft. Just the smallest thing, can have an impact like violent vibrations!