diff to drive shaft angle..

[JaneHibbert]

Hi, in the process of working out what vibrates on my car i have ruled out loads of things, but was wondering if the angle of my drive shaft to diff might be the cause, here are some piccies. It is not a steep angle, but it isn't 'straight on'.[frame][/frame][frame][/frame]

[MarkyB]

It looks OK, you could try moving it round to go in the next set of holes. 180 degrees I think.
What is the nature of the vibration and when does it occur?

[JaneHibbert]

Im not sure what turning it 180 would do, by wrong angle, not flush, i mean the drive shaft meets the diff at an angle, so that their is an angle all the time between the flanges.[frame][/frame]

[JaneHibbert]

should the drive shaft actually hit the diff straight on is what im asking really.

[JaneHibbert]

if so , is it possible to twist the axle so it does meet the prop shaft straight on?

[bmcecosse]

No! The diff must be in a parallel plane to the gearbox - the prop shaft then runs with equal angles at each end.

[JaneHibbert]

umn... NO to which bit

[JaneHibbert]

im thinking you mean no to it needing to be straight on? A the moment the gearbox is 'level' in relation to the car, and so is the back axle / diff, but that means the gearbox is slightly higher than the diff, so this is okay then BMCECOSSE?

[Bazzalucas]

The propshaft can be angled to the diff as long as it is "canceled out" by the angle going into the trans. I.e., both angles must be the same, just, uh, opposite....sorry, it's been a long time since I took Geometry, but in short, yours looks fine. The propshaft vibration can sometimes be improved by rotating it in relation to the diff flange 180 degrees, which is what the other advice was about.

[bmcecosse]

Yes - yours is perfect - although it looks like the prop shaft hasn't seen any grease for a while....does it have grease nipples?

[mike.perry]

The purpose of the universal joint at each end of the propshaft is to allow for it to rotate at an angle to the diff and gearbox.
Causes of vibration could be wear in the UJs, feel for sideways movement in the propshaft, or an out off balance propshaft. Subtitute for another prop, try it on another car or have it rebalanced professionally

[JaneHibbert]

Right, so angles good. Brilliant! Thanks everybody for putting my mind at ease.

Only one of the ujs has a grease nipple, a friend greased that for me as my gun didnt work, but that end you see in the picture doesnt have a nipple. Is there anyway of greasing it without a nipple?

Really i would like both ujs replaced and the prop shaft balanced. anybody know where you can get that done round manchester? Plus, of course, how much that might cost?

[JaneHibbert]

oh, i tried another on my car by the way, that made the vibration worse! Yet, that one worked fine on the car its from? I think a straight balance and new ujs are needed.

[mike.perry]

If there is no grease npple on the UJ then it is supposedly sealed for life, so one less thing to grease

[bmcecosse]

I have to say - it's highly unlikely to be the prop shaft. I won't go as far as saying ' It's 'never' the prop shaft ' But really - if you can't feel any obvious movement - that's not the problem.. It would be worth turning the flange 180 degrees - just to see if it's any better (or worse)......

[JaneHibbert]

Oh, BMCECOSSE, I did do one thing you suggested before, I changed the exhaust from a stainless one to a steel one and that has cut the noise down a lot, not fully, but a lot! thanks

[JaneHibbert]

it's weird though how turning the flange makes a difference

[mike.perry]

I have had two out of balance prop shafts, one on my ex GPO van and one on my Series MM

[kennatt]

what other things have you ruled out? why do believe its the prop,when does it come on ,or is it there all the time.

[Dominic]

The angle of the prop shaft will of course be changing slightly all the time when the car is being driven. As the axle moves vertically when going over bumps or as the car rises or fall in relation to the wheels (think of going over a hump-back bridge when it feels as if you're taking off!) this will be changing the effective difference in height between the output of the gearbox and the input to the diff.
Dom