I have just noticed that the splined part of the prop shaft that goes into the gear box is keyed, ie it will go in one of two ways. I rememeber mickyb saying that there is a right way and a wrong way to mount the prop shaft but does this just apply to the stock shaft as its balenced to be mounted one way?

 

When i fit my new single piece shaft can i just mount it either way?

Yes it's just the mounting together of the 2 prop sections not the end that goes in the box ;)

cool, ill just shove it in then! Its the spline on the new single piece that is keyed, where it goes into the gear box. I take it that is to help me align the bolts up to the diff.

Right I have put the new prop on and bolted it up tight, i tightened it like you would a wheel so its on flush and straight. The only worry I have is that the spline doesn't appear to be pushed into the gearbox all the way. When i mounted it i pushed the spline all the way into the gearbox but had to pull it out about 2cm for it to bolt tight onto the diff. Is it normal for the shaft spline not to be pushed in all the way? Is the rear gearbox oil seal still going to seal or am I going to have a huge oil leak when I drive it?!

 

And yes i did remember to put the gearbox oil back in!

bump!

maybe a silly suggestion, swb prop?

nope, was custom made. It is exactly the same length as the stock one i gave them to copy.

nope, was custom made. It is exactly the same length as the stock one i gave them to copy.

more than likely this acts as your sliding yoke now its a one piece,compensates for the diff "tramping" under hard load

Plus the fact that if it was the perfect length you'd never get the rear flanges together LOL

Flange... :D

Flange... :D

 

:rolleyes:

Yeah thats what i meant, had to push it right in the gearbox then pull it out a bit to get it over the, er Flange and bolt it on!

 

Is the rear gearbox seal i can see just a dust cover or something then? mmm Fingers crossed

Don't worry it will seal :)

Right the seal seems to have worked, got no oil leaks.

 

Have got some vibration between 65-70mph tho. Not much but it is noticable. It seems to be getting better but its still there.

 

I had the prop fully rebalenced when it was shortened.

 

Whats the best fix for this, just remounting until I get it right?

Right the seal seems to have worked, got no oil leaks.

 

Have got some vibration between 65-70mph tho. Not much but it is noticable. It seems to be getting better but its still there.

 

Whats the best fix for this?

 

A large jubilee clip

eh?

eh?

Your prop sounds as if its not properly balanced try putting a jubilly clip around it and driving at the same speed then tuning it until you get it right. ;)

ahh good idea, might be worth a try

I had this on another car when I went to a single piece prop.

After researching the subject I found that u/j's like to work in pairs cos they do not transmit a constant angular speed individually.

ie if the front joint bends the prop upwards say 3 degrees, then the rear joint should bend 3 degrees down for the cyclic vibrations to cancel each other out.

 

Now this is just a theory, but it may be that the engine and diff are not at the same angle, so to get the u/j's at similar angles then one bit of the prop may bend at the c/v joint. But if you take the c/v joint bit out then the u/j's must be at similar angles.

 

I checked mine with an accurate plumb bob and found the engine and diff were different angles, by about 2 degrees. I had adjustment built in to the diff as it happens so I altered the angle of the diff, and the vibration dissapeared.

 

Ps, to the engineers out there, I realise this is a simplified version of u/j theory.

mmm ok, anyone know if the diff is adjustable on the z? Ps the prop has no cv joint, just a uj at each end.

Yes but the tt prop you took off had a c/v joint in it, from memory anyway.

I'm not saying this is your problem, only that it may be.

The only way to alter the angle of the diff would be to alter the thicknesses of the front rubber/poly mounts, or get some eccentric rear diff mount bushes, which is what I intend to do with mine if I can't get the engine at the same angle as the diff, as I will be using a one piece on mine shortly.

The thing is there are 2 vibration sources in a prop. One is out of balance and the other is cyclic variations in torque. If you have the 2nd type then no amount of balancing will bring it back.

OK thanks. Its worse when you come off the gas at about 70mph, ie the torque/stress is pushing the other way. I might try the jub clip option first as its easy.

 

Ps I still gotta come and dribble over your v8 at some point!

Dribble, dribble.

Yes, balancing is the first thing to do, to either cure it, or eliminate it.

Altering angles won't be a 5 minute job.

I had 2 poeple try and balance mine before I realised it was an angle problem.

this is one of the reasons i dont see the sense in a one piece prop,the engines rubber mounted and moving around allso the diffs angle is changing a couple off mm,s and without a joint to compansate for the angle changes how can this be good for output bearings on box and diff :confused:

try taking the prop off the diff flange move it round one bolt hole at a time till the vibration goes.a bit of trial and error but it can work.