Front Prop Shaft UJ's

GTSX · Jul 9, 2009

I always thought the yolks on a prop shaft where supposed to be in line however having taken the front prop off my 300TDI to change a UJ I as surprised to see they are a little off set between the diff end and the gearbox end.

Is this normal or has someone been messing about with them in the past.

I did stop and look at a 110 and sure enough rear prop in line as I expected but the front slightly off line.

So should the UJ's on the front prop shaft be at about 45 degree to each other???

Any pictures??

The Mad Hat Man · Jul 9, 2009

offset - NEVER re-align a prop shaft - they are balanced items and should not be altered.

GTSX · Jul 9, 2009

NEVER re-align a prop shaft - they are balanced items and should not be altered

Really! So suppose the sliding joint drops out on the floor by accident - you're saying you need to get it put back together and balanced by an expert or something?

andyb66 · Jul 10, 2009

It doesn't need to be rebalanced by an expert you will soon know when you drive it if the prop is out of balance.

IME some LR front props are 'out of line' from the factory, so there is nothing intrinsically 'wrong' with it.

The Mad Hat Man · Jul 10, 2009

GTSX said:
Really! So suppose the sliding joint drops out on the floor by accident - you're saying you need to get it put back together and balanced by an expert or something?

No - what I am saying is that you arent taking enough care.

Before removing any propshaft you should mark the mating faces at both end of the prop shaft, so that it can be fitted back in the same position and, if you dont takle care removing the complete prop shaft, or your need to split it for some reason, then you need to mark the two halves so that you can re-assemble in exactly the same position. If you dont do that, then it is likely to be unbalanced when you refit, with associated juddering, wearing out of new UJ's and bearing - and yes - you will then need it rebalanced professionally, unless you are extremely lucky.

It is good engineering practise to mark items so that they can be refitted in the same position as when removed.

andyb66 · Jul 10, 2009

You don't need to mark the ends of a prop shaft before removing as long as the two halves of the prop don't come apart then you will be fine. The two ends of the prop shaft are phased with each other to give a constant velocity over the length of the shaft.

I agree it is good practise to mark the position before removal and it certainly can do no harm.

If you are just changing the UJs in a prop then there is not need to split the prop into it's two halves. If you do have to then you will definately need to mark them to make sure that they are back in the right place. However, if you know a little about prop shafts and phasing and sinusoidal velocity curves then you should be able to rephase the shaft on your own.....

.....unless of course I have just been lucky for the last 20 years

No offense intended towards MHM, but I think that our experiences in these matters have been different. I am not calling your practises or experience into question

The Mad Hat Man · Jul 10, 2009

Andy - I agree - yu dont have to mark the ends of a prop - but it can make life a lot easier to refit if you do, especially if the 4 bolts are not on a "square" pitch. It is is just good practice and one that may help. It doesnt take long and occasionally becomes invaluable. The same with any sliding coupling - 2 minutes to mark it - or, possibly, an hour or so of trial and error - it makes sense to me and has become normal practice.

To someone, such as GTSX, who may not come from an engineering background, safe is better than sorry.

andyb66 · Jul 10, 2009

The Mad Hat Man said:
To someone, such as GTSX, who may not come from an engineering background, safe is better than sorry.

(insert shake hands icon here)

Davec · Jul 10, 2009

Normally a propshaft should have the gearbox out put flange and the diff input flange parallel to each other, and the UJs lined up. On coil sprung Land Rovers this isn't the case at the front, the flanges aren't parallel, so the UJs are out of line to compensate, this is correct, although 45º sound a lot.
As others have said, reassemble as it was taken apart.

The Mad Hat Man · Jul 10, 2009

andyb66 said:

is that better?

andyb66 · Jul 10, 2009

The Mad Hat Man said:
is that better?

LOL.

Brilliant

classic kev · Jul 10, 2009

I would have thought there should be aligment marks on the prop shaft; there are marks stamped onto the props on my RRC and the workshop manual shows where the alignment marks should be when you put it back together after overhaul.

GTSX · Jul 10, 2009

OK 45º is a bit of an exaggeration probably 30 something degree. It just seemed odd to be like that and not lined up as I expected.

GTSX · Jul 10, 2009

Anyone got a good clear pic of the front prop shaft they can post up or send me?

Front Prop Shaft UJ's

GTSX

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