Prop advice - now stop me if im wrong here......

[TouringMatt]

Just dropped the diff off the car. (doing the subframe bushes)

Now im sure its suppose to disconnect from the prop where i unbolted it, just around the rear beam area.
Now im pretty feckin sure about 3 foot of prop is not suppose to slide out with it.


From what i can see there is a locking nut that attaches the two bits of prop together, looks like i need to drop the complete exhaust off and remove the heatshields to do this great another job

Is alignment of the splines critical? I had marked the diff end of the prop so know roughly what position it came out

Had noticed a clank from the prop when i was under the car some time back, figured it was something worn out...........

Last time i trust someone else to fit something


Some advice would be nice

Matt

[LateM3]

I'm sure the Prop shaft is balanced as a single unit, so should be re-assembled as it came off the car. I believe there is a dimple stamped on either half near the centre joint and should be lined up.

[old_skool]

Is alignment of the splines critical?

I'm sure the splines need to be marked when separating the prop as there is no "master spline". If my thinking is correct in this then the prop will have to be re balanced

I wait (hopefully) to be corrected

Don't know about a dimple. Let me know if you want me to have a look at mine if it helps dude.


Hope it's ok Matt.

[LateM3]

http://www.s14.net/forums/showthread.ph ... &highlight

Courtesy of Demlotcrew, pics on second page, as it says marking before separation doesnt guarantee it was aligned in the first place! Look for the dimples before removal, if obscured by rust, marking it yourself is the next best option.

[tommype30cab]

i did this a little while ago mate. Basicly the person who fitted the prop didnt do up the large nut that connects the 2 halves via the centle spline tight enough. I put mine back togeter and it was aboslutely fine and has been shake free for about 3 months. usually there are no problems but i believe in the odd case it can vibrate. My advice would be to re fit it and hope its ok. If its not then source a second hand prop cos re aligning it with that many splines would be a bit of a pig me thinks. best of luck!

[Brianmoooore]

With an E30 prop, you fit it together so that the U/J yokes on the end of each half are exactly in the same plane as each other. There's only two ways that you can do this, so you have a 50:50 chance of getting it right the first time.

[TouringMatt]

Cheers for the advise guys, i'll let you know how it goes

[TouringMatt]

Ok, got the exhaust and shields off.

Rotated the gearbox side of the prop, found a white tipex dot, matched it up with the one on the diff side of the prop. With the dots lined up the UJ's are slightly out of line, rotate the prop one spline and the alignment of the UJ's are almost spot on.

Are the dots just there to show the correct side and as you said Brian the UJ yokes have to be on the same plane?

Cheers,
Matt

[Brianmoooore]

Personally, all this stuff about dimples on the prop are news to me. May be correct or not, but I always put my own marks on. Same with cambelt timing marks.
Since these marks are in tippex, i would think some one's had it apart before.

[TouringMatt]

Well, more white paint than tippex!

So the UJ's being aligned the the critical part?

[Brianmoooore]

Well, more white paint than tippex!

So the UJ's being aligned the the critical part?

No, splines being mated exactly as they were when BMW balanced the shaft at the factory is the critical part, but, since the shaft was originally assembled with the yokes on each end in the same plane, there are only two ways it can be assembled, and only one of those is right.

[TouringMatt]

Ahh right, 50/50 chance then

Subframe has just touched down, apart from a sticky bowden is been fairly good going - fatal last words........

[Templ8e30]

All e30 prop's i've removed have had 2 white dots to mark the position and almost all of them have had the marks prefectly aligned but have the knuckles slightly out of line

The prop for my 2.7 was like this, tried first time to line up the knuckles rather than the dots and it vibrated like hell. Removed it all and lined the dots up and the vibration disappeared

Would have been a much better idea for BMW to make them with a master spline to avoid all this trial and error

Cheers,

Iain T

[TouringMatt]

All e30 prop's i've removed have had 2 white dots to mark the position and almost all of them have had the marks prefectly aligned but have the knuckles slightly out of line

The prop for my 2.7 was like this, tried first time to line up the knuckles rather than the dots and it vibrated like hell. Removed it all and lined the dots up and the vibration disappeared

Would have been a much better idea for BMW to make them with a master spline to avoid all this trial and error

Cheers,

Iain T

Superb, thanks for replying mate

Matt

[Templ8e30]

Hope you get it right first time buddy

Cheers,

Iain T

[SGP]

Every one I've split had the white dots aswell.I didn't think it was neccessary to remove the diff or propshaft to change the bushings though !

[Brianmoooore]

All e30 prop's i've removed have had 2 white dots to mark the position and almost all of them have had the marks prefectly aligned but have the knuckles slightly out of line

The prop for my 2.7 was like this, tried first time to line up the knuckles rather than the dots and it vibrated like hell. Removed it all and lined the dots up and the vibration disappeared

Would have been a much better idea for BMW to make them with a master spline to avoid all this trial and error

Cheers,

Iain T

Something odd about this.
A U/J working at an angle, unlike a CV joint, does not transmit the motion at a constant angular rate.
The propshaft actually slows down and speeds up slightly as it turns. The second U/J works in the other direction and removes this effect, so that the drive into the diff is smooth again.
It's only a small effect at the angles the U/Js work at, but it would be bad engineering practice to assemble them in any other way than exactly in the same plane, and BMW don't do bad engineering practice - they leave that to the French.
All the half dozen or so E30 props here have their yokes aligned exactly.
I've just given one a polish with a rag, and sure enough, under the grime, are two white dots!

[gareth]

i've never seen white dots on mine but then i've not actively searched for them! i'll remember to look next time i'm under there though

has anyone noticed how much the UJ's wear and get 'set' at one (straight ahead) position?! not much use for anything other than a nicely aligned E30! mine have all had a sweet spot, after that they get noticeably tighter

[Brianmoooore]

i've never seen white dots on mine but then i've not actively searched for them! i'll remember to look next time i'm under there though

Same here, until I checked one today.
That's three things I've learnt about E30s today! (Other two are: "E30 fans can be orange plastic", and " exhaust rocker shaft on a M20 can be removed through the centre grill aperture without moving the engine")

Propshafts with U/Js should never be installed straight to prevent the one spot wear in the joints. Input and output shafts should be parallel but the bit in between should be at a slight angle.
E30 one is designed to be a little bit too much on the straight side, IMHO.

[TouringMatt]

So im okay to line up on the dots with the UJ's slightly out then...............?

I didn't think it was neccessary to remove the diff or propshaft to change the bushings though !

Its not, but im changing the brake lines and sorting a few bits of rust on the tank too

[Brianmoooore]

So im okay to line up on the dots with the UJ's slightly out then...

I would say not. Can't explain Templ8e30's experience though.

[TouringMatt]

OK, props on. Lined it up with the UJ's running true with each other, white dots on the same side.

If there was vibration how bad would it be?
Up to 70 it seems normal, 80 to 100 i get some but i dont know if a, im being over sensitive to everything i hear and feel or b, my wheels are not balanced correctly

Cheers,
Matt