wierd vibrations under the floor.help me!

hey guys,i need a little help.I have a 50 8ba,c-4 auto trans.All rebuilt and runs like a champ.When i hit the freeway i will do 60,when i back off for whatever reason,i feel a vibration directly under my excelerator pedal,its not really viguorous,but very noticable,until i hit say 55 and it stops,i am not feeling it in the drive shaft just uder the pedal,like a rubbing motion.I dont know what do you guys ...any idea.should i keep driving till i get it checked out?..thanks guys.

 

i've lost a wheel weight on my work truck shakes from 60-65 under or over it's fine,

 

tire needs balanced maybe? My buddy had that problem, one of the motor mounts was bad. When he let off it at highway speeds his pedal would vibrate.

 

The vibration is right under the pedal,i dont know about a wheel weight,because theres no shaking,just rubbing,vibration.

 

could be pinion angle, or a drive shaft balance issue, what happens if you shift to nuetral and coast down from 60. find an open road and try some different things to isolate it, coast in nuetral engine running, coast with engine off. see it it changes. is the exaust hitting the frame or underbody anywhere. ive seen where the driveshaft was made to long and the slip yoke would bottom out on the trans output shaft and cause a vibration. hope this helps.

 

Tires were recently balanced,thanks

 

Check your exhaust , it may be bumping the floor pan just when you are letting off the tork of the motor, just get under there and bump on the pipe youll no if it is .,and if thats the problem put a ruber shim between the floor and pipe. Some times the exhaust is closer than you think . Good luck ... Just trying to help .

 

i would check the engine and trans mounts by jacking each up and looking for the rubber seperating.when you are accelerating the engine torque will try to lift the driver side of the engine up and being that is in close proximity to the brake pedal it could be causing something to come in contact.hopr this helps.

 

thanks guys you all have great ideas and will check each one out,thanks again

 

I had the same problems and it turned out to be a broken motor mount

 

Just had a friend finish a new frame off rebuild in a 36 Ford Sedan. Car is a nice driver but had a vibration from the floor area. We put it on a rack and found that the standard trans was rubbing the floor in one spot. We did a little bending and all is well. It is amazing how much vibration that can come from anything that the motor or trans will touch. It seems to telescope through the whole car.

 

Consider getting the floor balanced.

And have a p***enger move around in the car and see what they feel. The vibration might feel right under the pedal because that's where your foot is.