Hello All,
I've got an '89 S4 with 109k miles.
I recently rebuilt the engine, it was purchased as a non-starter.
In the process of removing the engine for the rebuild I seperated the flexplate from the coupler. I neglected to index the two with marks. I have since
read in the archives, that they are balanced as a unit (together). I can find no reference to this in the WSM.
This brings me to my problem.......
There is a slight vibration between 2k and 3k when reving in neutral.
When under load (on the road) there is a signifigant vibration throughout the
entire car. It increases in amplitude with the load. In other words the harder you accelerate the more profound the vibration is. If you slowly apply throttle
the vibration is barely noticable.
I'm trying to avoid removing the lower bell housing and exhuast etc. to move the coupler "one bolt hole at a time" in rotation to see if that brings equilibrium. Six bolt hole leaves five possibilities. Not so bad I guess.
However, If someone can say these items are not balanced as a unit, I can look elsewhere. Possibly Harmonic balancer.
Should these V8's tach up smooth as silk in park or is there a harmonic to be expected somewher in the rev range.
I suppose I could disconnect the the coupler and see if the vibration exists in the engine only......Oh well.
I am hoping someone has BTDT.
All speculation appreciated.

Coleman

 

Not sure about your 84 MY but on the 78's there are 6 bolts but only three position options. I've moved mine around without indexing with no resulting vibrations. IIRC the flexplate itself is balanced so any position should be OK. Have you checked to make sure the torque tube housing is properly mated to the bellhousing?

Dennis

 

Thanks Dennis,
I'll double check all my mating surfaces for the bolt-up. It's also nice to know
there may be only three possibilities for the coupler to flexplate attachment.

Thanks,
Coleman