vibration

[Bangers77]

Hey guys,

I've been trying to chase down a vibration, it occurs from around 40k's & up. I've replaced the uni's front & rear, I haven't had the tail shaft balanced as yet,

However when up on stands I removed the tail shaft to try & eliminate where it may be, when running through the gears the vibration is still there mainly from around 2nd to 3rd gear. There seems to be a bit of play on the output shaft when I put the yolk into the back of the gearbox???

Any ideas would be greatly appreciated

Cheers Mark

[GEOFF289]

Is the vibration new, i.e. has it just appeared in a previously smooth running car? If so, something has broken or cracked or something to create the vibration

If it's always been there I'd be checking it has the correct balance flexplate or flywheel on it. Engine mounts? Trans mount?

Put up some details of your car - year, engine, trans etc - to make it easier for the knowledgeable people (not me) on here to help you.

[Bangers77]

66 coupe, 289 C4. all stock condition

I've owned the car for 6 mths now & the vibration has always been there, just a matter of going through the process's. Checked all engine mounts & gearbox mounts, seems to be a bit of excess play in the rear gearbox bush in the extension housing.

Uni's have been changed as they were a little worn.
 
I might have to look into replacing this & continue from there.

Mark

[GEOFF289]

I don't know if excessive end play in the output shaft would result in a vibration but I would still be having a look at the flexplate. A 289 should have a 28 ounce one, if someone has put a later 50 ounce one on it it will vibrate.

Just whip the inspection plate off and turn the engine over by hand til you can see the weight and compare it with a google search for the two different plates. The 50 ounce ones have a noticeably larger weight, it's easy to tell.

[GLENN 70]

You have to work out if it's speed related or engine rev related . In park slowly bring the engine revs up and see what happens .  If it's smooth and seems normal try driving at say 60 kph and slip it into neutral till it slows to the speed you say it happens ,try this a few times .

[barnett468]

....also, if the vibration is in the engine portion and is consistent when it occurs, it is a dynamic imbalance . if it oscillates/cycles as in strong weak strong weak etc, it is harmonic.