The Dodge Challenger Message Board

I have no idea why but when I hit about 80 MPH in my 73 Rallye the center of the car vibrates like the cars going to fall apart. There is no vibration in the brake or gas pedal or steering wheel, I only feel it where the center console is. There are absolutly no other vibrations until I get to about that speed. I have New Tires and just got everything balanced thinking it might be that. I also checked to see if the drivetrain is twisted or off balance neither one was bad. The only thing I can think of would be the motor mounts it appears that the left side is broken but I was told that wouldnt do it.. Any suggestions???
Norm

Rear Engine/transmission mount is toast. I just replaced mine and it runs SMOOOOOOth.

We had a bad vibration that got a bit better at 45-50mph but then came on again even worse over 65mph. It felt mostly in the centre console area.

The transmission and engine mounts were new.

We had the wheels and prop re-balanced. Small difference but not much.

I had the rear spring arch camber increased to give a bit more height at the rear. That changed the pinion angle a bit and again the vibration got a little better. Only a little though.

The big change came when I removed the crank pulley and cleaned the paint off the crank balancer where the pulley sits. I had brush painted it and wondered if the pulley was not sitting quite flush. I also checked the back of the pulley was flat. This made a huge difference! About 85% of the vibration went 'just like that'.

I then changed to manual steering so the steering pump was removed. This got rid of a bit more vibration.

The only vibration now comes on at speeds over 80mph and gets steadily worse the faster I go.

I have noticed that my worn looking rear drums have some HUGE ballance weights on them. One side much more than the other. Are they on the right sides? Do they need machining true and re-balancing? Time will tell. I will look into this next winter. I can live with it for now.

so dave. is the vibration still in the console area?

No. It is just a general sort of vibration now. the console tends to amplify vibrations I think. Like a sound box.

my 74 was doing the same thing about 55 mph and got worse so I had my tires ballanced. Now the vibrations start at approx. 72 mph. I thought my next thing to check is the driveshaft. How do I know if there are bad or wrong or to many weights on the rear brake drum? Anything else to check also?

I want to know the same thing!

After checking the driveshaft it could be lots of things. Worn bearings in the transmission, a slightly bent con-rod. Badly ballanced engine etc.
Even a bad spark plug!

But if the vibration NEVER happens at the same rpm in any other gear except 'Drive' or 4th or does so at different rpms but the same speed then it has to be something out of balance after the transmission. So it has to be in the driveshaft/axle/wheels(front or rear).

If your car can hit 72 mph in second gear as well as 3rd see if the vibration is any different in either gear.

Lower-price/badly fabricated/retread tires might cause this kind of problems. Another factor is if tires have been sealed with liquid-in-a-bottle.
I do not think these factors cause the problems in your case but I think it´s worth mention.

might as well check in to all of them. I guess it wont hurt anything.

If you got another set of wheels, try them and see if the problems remain. Then you can exclude that factor.

thats what I did first. Thats why I got my tires re-ballanced. It's not as bad but it is still there.

also find out if the vibe is there while engine is out of gear stopped and revved, or while going down the road take it out of gear to see if it goes away i had this problem with mine and it turned out the driveline was out of phase (someone had welded the u-joint back on wrong!)i had it rewelded and balanced and no more bad vibe

well, I took my drive shaft off and went to have it ballanced. I showed it to them and they just laughed. they said someone had made this one fit on the car by cutting and welding. he said the only way he could fix this one is by putting a whole new tube in it. so he did and now with that and new u-joints I have a whole new drive shaft and the vibrations are gone!!

Nice one! It's a good feeling when something goes right isn't it?

heh i thought I was the only one,,,,lol