Miguel Macias

i have a 66 coupe that starts vibrating when i get to 55 mph and let off but i have already balanced the DS and new u joints and a new tranny mount but it still keeps vibrating can you guys help me its a c4 automatic tranny with a inline 6 engine

dawson1112

It only vibrates on the coast side? It runs smooth as long as you on the gas?

You could have a bad rear wheel bearing , or the coast side of the ring&pinion gears are worn. If the vibration sounds like a chuckle it is the rear differential . Have you checked fluid level in the rear end lately

Pay attention to where you feel the vibration coming from, what part of your body feels it most intensly?

Left side / right side? In the seat behind you or the floof under your feet.

Steering wheel seem to vibrate a lot when it occurs , could mean a bad tie rod or ball joint.

rmodel65

did you replace the tailshaft bushing when you got the new driveshaft?

Miguel Macias

no it will vibrate when im on it too but it vibrates more after letting off and i hear it right were the tranny is at

Miguel Macias

rmodel65 no i did not change the bushing

rmodel65

i would definitely take a look at that bushing

Gun Jam

Yes a worn tailshaft busing can cause lots of problems. If its worn so is the slip yoke. You'll have to replace both the yoke and the bushing.

Press up and down on the yoke where it enters the trans how much play do you feel?

-Gun

Miguel Macias

their is only a tiny bit of play

Gun Jam

is it possible that you bent the yoke bearing holders when swapping out the u joint bearings?

When did the car last run right?

What was the last thing you changed on the car before you noticed the vibration?

How long has this vibration been an issue?


-Gun

Miguel Macias

like a month and a half ago i noticed it and last time it ran right was in February 14