Vibration is driving me nuts!!!!!!!!!!Any help please

[stephen4785]

I swaped out the intake on my 65 with a weiand excelerator and put on a holley 670 street avenger.Couldnt get the holley tuned right so I put my edelbrock 650 back on.Found out the reason it wasnt running right was because the vacum cap I put on the manifold was split.Now when I take off I get a bad vibration(it feels like it comes from the rear) at about 15-20 then really bad at 50-60.It smooths out at 60mph and doesnt return unless you get down to 50ish again.The manifold gaskets leaked when I first put them on so I removed them and replace them then used a different silicon.I changed out my plugs and it didnt help.Put my car up on the lift at work and check to see whats going on.One u-joint was bad so I replaced both of them.Still didnt help at all.I checked the tranny mount and its still good.The motor mounts are brand new.The weight isnt nocked off of the driveshaft or anything.It only vibrated really bad at 50 when your giving it gas.And when I first take off once its cooled down itll shif itself into 2nd gear(green dot C4).I think do to the vibration untill 20 mphI rotated the rear pinion to see how much play there is and it does have some play in it but it doesnt move up or down at all.I didnt have this problem before I swaped intkaes and carbs.And it did the same vibration with the holley and the edelbrock.

 

[jikelly]

That is really strange. Could it be a fuel/ignition problem. Maybe like somehow one cylinder is not firing. I would check your distributor and maybe just replace the cap a rotor. If you still have points you might check their dwel or gap or whatever they call it.

 

[WORTH]

YOur gonna have to figure out if it's engine or drivetrain, take it for a ride, get it to vibrate, and play with the gas, slip it into neutral, do as many different things as you can to determin where it is, engine or drive.

 

[70XR7ConvertCat]

Three things to check:

1. You threw a wheel weight.
2. Play in the transmission tailshaft?
3. Unbalanced driveshaft.

Steve C.

 

[lauras70mach1]

Is your engine externally balanced? Maybe the hub spun on the harmonic balnacer?

 

[Ozsum2]

With it n Park, rev it up to varied rpms while still in the driveway. This will tell you if it is engine related. If it isn't then it is drive train related and you should begin checking the various components.

 

[stephen4785]

Ill check to see what I can figure out.If its the drivetrain or motor.Ive got a mallory unlite and mallory promaster coil on it.Ill drive it to see if its the motor or not.I think its the drivetrain but Im not sure.

 

[Ozsum2]

Ill check to see what I can figure out.If its the drivetrain or motor.Ive got a mallory unlite and mallory promaster coil on it.Ill drive it to see if its the motor or not.I think its the drivetrain but Im not sure.

If it doesn't do it in the driveway, try to see if you feel it in the steering wheel, or on the seat of your pants. Basically, front or back.

 

[stephen4785]

Well I shifted it in nuetral when it started vibrating and it stoped. I reved it up a litlle bit and when I got to a certain rpm it started shaking. Im thinking its the motor now but I still dont know whats making the vibration.

 

[PONY XPRESS]

Double check: vacuum, timing, firing order, fuel pressure. Check for cracked cap, rotor, other elec leaks.

 

[TOM B]

check the balancer to see if the rubber is torn. dont use the front and rear mainfold seals, instead use a good silicon and put down a 1/4 inch bead.
did you get the distributor and wires back on right.

 

[Ozsum2]

Have someone do the throttle like you did, while you listen at the rear exhaust for a miss. If not, I think it is a motor or tranny mount. These things can be hard to spot with weight on them, but basically you are looking for ANY crack or separation of the rubber.

 

[stephen4785]

well i narrowed it down to the motor because the vibration gotten to where I can hold the throttle a little it does the vibration.

 

[VictorII]

well i narrowed it down to the motor because the vibration gotten to where I can hold the throttle a little it does the vibration.

Last year my dampener cracked at the bolt hole letting it move a little at a time. After a few weeks the key way was hogged out enough that it felt like an out of balance pressure plate. Luckily I had and extra dampener and that took car of it. Drove me freakin' crazy. Your damperener bolt could also be loose. That would let the unit move about as well. You can check the dampener by looking at the timing and looking at the crank pully to see if it is straight when it is running. If eiter is not how you remember from before, check it out. It sounds like rotational vibration. If you are like me, things happen tww or three at a time, and rarely one at a time, like a flat tire or something like that.

 

[stephen4785]

I know what you mean.Now Iv got that vibration,my steering wheel just decided to come off last night,and its getting hard to start then backfired last night.

 

[66SilverStar]

are you sure that you got the right gaskets? or maybe they could be on the heads wrong? also do you have the correct flywheel to match the engine balance?

jimmie