91 Z Vibration

[intimidatorz34]

I am getting a vibration (the entire engine seems to shake) when I start the car, step on the brakes as its coming to a stop, and when it shifts into whatever gear around 55 mph. I would think it to be a lower engine/tranny mount but not sure why the entire front would shake when it is in this gear. (and its not alignment, etc.) Any Ideas? The upper mount is a new (5k miles) polydogbone. And if it was a tranny, I wouldnt think that it would shake when in park. Then again why is it shaking so bad in that certain gear unless its at a certain resonance.

There arent any codes and the timing belt is fine.

[pocket-rocket]

Did it do this before the poly dogbone? If not, the vibrations were always there, you just didn't feel it because the rubber in the stock dogbones absorbed it, and the poly one transmits it to the body.

[intimidatorz34]

Did it do this before the poly dogbone? If not, the vibrations were always there, you just didn't feel it because the rubber in the stock dogbones absorbed it, and the poly one transmits it to the body.

Nope, Ive had the poly for a while.....it is just a recent thing, especially when it shifts into 4th around 55, I feel like im coming in for re-entry.

[pocket-rocket]

What shape are your plugs and wires in?

[intimidatorz34]

What shape are your plugs and wires in?

Plugs, wires, most sensors including knock are all new within the past 7k miles because i took apart the motor for the o ring leak.

[pocket-rocket]

Ah, I just thought of it. Axles. Some vibrate at certain speeds when bad. Sometimes they vibrate more when you are on or off of the gas (when they have tension on them). I would check them out, especially if you think they are original, and have alot of miles on them.

[intimidatorz34]

Ah, I just thought of it. Axles. Some vibrate at certain speeds when bad. Sometimes they vibrate more when you are on or off of the gas (when they have tension on them). I would check them out, especially if you think they are original, and have alot of miles on them.

This wouldnt cause vibration when not at speed and in park. I was messing with it today, and when it idles it shakes pretty bad, but then i can rev the throttle by hand and the engine stops shaking. But this still doesnt solve the shaking at speed. Plus I have noticed a little coolant on the distributor cap, so looks like intake gaskets may be going. (Dont think it is risidual cause I have run the car 200+ miles since I had the thermal switch under the throttle body out.

[pocket-rocket]

Yeah, I know it wouldn't do it in park, you mentioned about it doing it at speed, so I assumed it didn't do it in park.