Club 80-90 Forums

http://www.van-cafe.com/home/van/page_1 ... shaft.html

simon

looks just like a GKN one which is cheaper and here in the UK

Yes it does and fair bit more expensive...

I have reverted to one of my VW shafts which seems to rattle less than the (perfect jointed) GKN one.

Interesting what you say about 'perfect jointed' shaft there clive.

I used to have zero vibration from my prop shaft, until i got the rear end of it rebuilt.
Since then it has albeit slight, but noticeable vibration at certain speeds.
I guess it could need balancing, given that bits were pulled out of it and pressed back in again.

But i have always found it quite fascinating that in the apparently notchy indexed state the rear joint was in, it was not noticeable in any way other than if you had the prop off of the vehicle!

Yes, lack of concentricity is probably as or more important than the last degree of balance

Clive wrote:The whole drivetrain compliance and alignment is a delicate balancing act in itself !

it was totally digital Alan, can't understand why it was fine before, but now maybe wants unbolting and rotating round in the hope of finding a lesser vibe

Oooh, sorry Aidan, i wasn't pointing any fingers or anything like that.

I just think its pretty interesting really. You would assume that a buggered joint like that would help to cause vibration etc wouldnt you.

However have pondered as to whether the vibration wasnt noticeable before as there was so much slack in the joint that it didnt transmit the vibrations along the shaft?

I guess the best thing would be to try shifting round as you suggest Aidan, and if that dont work send it off to be balanced and see if that made a difference.

Try turning it around completely, fore and aft?

Having read some of the american forums there is a laser tool available from go-westy for alignment of the front and rear boxes, whch includes making both drive flanges parellel to each other. This is done by raising or lowering one end of the box, dont know how it is done. This prop is supposed to eliminate the need to do this.

De-coupling eliminates all the vibe problems, but as the shaft is still going around when decoupled, does that mean that the vibes are not to do with balance, and make it something to do with the power that is being transmitted front to rear.

Just some thoughts..

I personally aligned the gearboxes using a bit of string tied at the front, and stretched out underneath, you cannot lay it adsactly on the case halves, so have to use your eye for the alignment.

Replacing all the rubber washer gearbox mounts, and the engine mounts would probably help too.

The first RX7 had a tunnel connecting front and rear gaerboxes and enclosing the shaft, I remember reading at the time that it was to stop these vibrations and resonances. Not gonna build one of those though!!!