why does my minor vibrate over 45 ?

[1969morris]

Not long had it and love it to bits but am scared to go over 45 cause it starts to vibrate but its not like a wheel balancing type of vibrate it is like something around the back end !! I have checked the diff and it has oil but it was very black so have changed that and is no difference but I did notice there were a couple of bolts missing out the back end of the prop joining to the diff !!! Could that be putting prop out of balance ? I wouldn't have thought so ! Has any body else had this problem?
Thank you in advance.
Stu

[smithskids]

Hi 1969, almost certainly the prop shaft. Should have 4 bolts in it, some have one hole on a different pcd. so you cant put it together wrongly. If it is same pcd move it round 90 degrees at a time and try it. If it is still vibrating get the propshaft balanced. Good luck.

[bmcecosse]

Obviously the missing bolts - fit new ones!!

[1969morris]

That's great news I will have look over the weekend. Was hoping it would be that but it seemed more serious and was dreding some really bad news about it! Thank you for your help . One little question what does PCD mean is it prop shaft drive ?

[bmcecosse]

That would be PSD..... PCD = Pitch Circle Diameter -so eg on a Minor the wheels are held on by studs with PCD = 4". As I remember - the prop shaft bolts are NOT on a PCD.......

[Trickydicky]

PCD= Pitch Circle Diameter. If you measure the holes across the centers this would be your PCD, as roy says the studs on the wheel are 4" as an example

[1969morris]

I get it now thank you I have just been under car and the rear has only 3 bolts and 1 has a different nut and washer on so assume now that this could throw everything out of balance. I hope it does the trick would love to take my minor over 45 without feeling like it will fall apart.
\thanks guys

[bmcecosse]

Don't just fit 'any old' bolt and nut - get the correct ones.......

[1969morris]

That was gonna be my next question about the bolts have looked up the proper ones out of the moss catalogue from david manners morris minor unless you can suggest anywhere better? I did think about just getting some from the local hardware but may not solve the problem.
What do you reakon.

[bmcecosse]

The correct bolts are 'fitted' ie very snug fit to accurately locate the flanges - just buy 4 new ones(and nuts!) - shouldn't break the bank..........

[lambrettalad]

New ones come with self locking nuts and when it's right ,mark the shaft end flanges and the diff and gearbox flanges ,so that if you have to dismantle ,you know how to put them back together

[bmcecosse]

They need to be the special 'low profile' self lock nuts - there is no room for ordinary SL nuts.

[David53]

Agree, get those bolts replaced but can also highly recommend new Uni Joints and balance the propshaft. Did this to mine a few years back and such a huge difference. Car was transformed, no vibrations whatsoever

[philthehill]

The correct bolts with the correct low profile nuts for attaching the prop-shaft to the diff flange are available from Bull Motif Part No: FIX150 @ £0.65.
There is a raised lip on the prop-shaft rear flange which fits inside the recess of the diff flange to locate the prop-shaft flange centrally against the diff flange (see attached pic) . Whilst the bolts clamp the two flanges together they mainly transmit rotational forces i.e. the drive; but they do need to be a good fit in the holes of both flanges because any movement between the two flanges increases the chances of shear.[frame][/frame]