I need advice,

If i place the engine with the crank at the same height as the diff center the sump will be too low.
What is the view about engine/crankshaft alignment with the diff, I need to raise my engine about 30mm.
Could I raise the engine and slightly tilt the diff by a few mm to recorrect the alignment, ensuring that both are in a straight line through the crankshaft, this would tilt the engine back about 10mm. I have enough space beneath the bonnet, i want to reduce any strain on the propshaft and i dont want to rely on the UJ on the prop for any misalignment.

Has anybody tried this .

Not sure whether this is what you mean...but....basically any setup you have you need to have the engine, transmission and diff parallel....they don't need to be in line or anything as long as they are parallel...so if you raise the engine and tilt it slightly you need to tilt the diff aswell by the same amount in the same direction....if there's a massive difference in height you'll need a prop with an extra UJ as well.....HTH and I'll try and draw a pic if you don't get what I mean.....Oli.

You need some misalignment with the prop, or it will wear out very rapidly. The roller bearings are designed to do exactly that, rotate in the bearing caps. If everything is in line, the rollers will be static and wear into the cap giving it a profile like an internal spline drive.

Like Oli said, everything does need to be parallel though

Very interesting that,

Wish I'd read that article before welding my diff brackets on

Will check tomorrow and see how far I'm off 3 degrees

See Ya

Rich

Thanks for all the advice. It looks as though I keep the line of the diff and the crank/gearbox primary shaft parallel and the propshaft does not exceed 3 degrees deflection then I should be OK. As the propshaft is approx 800mm long, I should manage to raise the engine enough to solve my problem.

Thanks again.

OH dear never thought of this eitherbut I am confused.
If the axle pinion and crank centre lines have to be parrallel within 3 degrees in a longitudinal plane do they also have to be within 3 degrees when looking from above in a plan veiw?
I am still confused also because if there is a uj at the gearbox and axle end why can't it take up any movemnt required. Also with a live axle linked as per the book that moves up and down the angles will change as will the angle of the prop flange (won't it?).
Like I said Im confused so can anyone explain it in simple terms please.

As an after thought I've welded my axle brackets on so that they are parrallel the the face of the pinion flange does this cause a problem?

[Edited on 25/1/06 by omega 24 v6]

I think with a live axle, the line through the diff drive always remains parralel to the crank/primary shaft.
As the axle rises and lowers the distance between the two lines changes (absorbed by the extention on the prop with the splined sliding section) but always remaines parralel. The UJ will absorb the change but try to keep this within 3 degrees.
If the Diff rotated as the suspension went up and down it would change the line of the diff drive in relation to the crank/primary shaft. this i think should be avoided.

I realise this proabaly makes no sense but i'm trying.

Ok, so on my car where I run the engine and gearbox at a slight angle to the car's centreline (2 degrees ish) and use a sierra diff, my diff is currently mounted pointing straight forwards.

This is not parallel, will ie be a problem??

If so, how do all the westfields which run the factory recommended engine/gearbox alignment angle but which use a live axle get away with it????????

You can't angle the axle to match the gearbox/engine so they cannot be parallel!!!!!!!

quote:

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Originally posted by omega 24 v6
OH dear never thought of this eitherbut I am confused.
If the axle pinion and crank centre lines have to be parrallel within 3 degrees in a longitudinal plane do they also have to be within 3 degrees when looking from above in a plan veiw?
I am still confused also because if there is a uj at the gearbox and axle end why can't it take up any movemnt required. Also with a live axle linked as per the book that moves up and down the angles will change as will the angle of the prop flange (won't it?).
Like I said Im confused so can anyone explain it in simple terms please.

As an after thought I've welded my axle brackets on so that they are parrallel the the face of the pinion flange does this cause a problem?

[Edited on 25/1/06 by omega 24 v6]

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To be honest unless your being really picky or are racing etc I wouldn't worry about it too much....if their not parallel you get more vibration and possibly increased wear rate depending on how bad it is.....for the amount of miles that most of our cars will be doing you'll probably not notice any difference at all! I'd go with what looks easiest (the straightest) and see what happens - if you get any undue movement its not a big job to fit some washers on engine mounts etc or on the diff mounts if your running IRS like me.....chances are you'll never notice! Oli.

It's right that parallel flanges with allow the UJs to compensate for each other's angular non-linearity BUT ONLY if the yokes are lined up right. I wonder if your average propshaft place will do this as a matter of course? I wonder how many get it wrong so the non-linearity is doubled. . . .
I'd have thought more than 3 degrees would be OK if it's lined up right - hope so I have over 10degrees on my front prop!!!
Further observation on the link above - it recommends altering the length of the lower trailing arms to adjust the axle pinion angle - do a lot of that & the geometry errors will be trying very hard to twist the axle under roll . . . . I wouldn't go down that road!
Bob

I was looking at a truck set up today and granted it does have a centre bearing but, from the centre bearing to the axle the prop is lying at an angle og at least 10 degrees. (needs a puzzled smiley here)

My view is I'm not going to worry about it!

In your (live axled) position, I think I would rose joint one end of each of your trailing arms and rubber/poly bush the other end.

That way you can adjust for any inaccuracies, and alter the diff nose height as well, then you can cater for any issues anyway.

The hot rod guys alter the nose of the diff to point down and say it gives better traction off of the line as it's trying to drive itself down onto the tarmac ( even more puzzled by that statement.

Yep, same in grassin on the class 3's............and no I don't really get the physics of it either!!!

seems to work tho!

It's really not the kind of thing to get in a knot about to be honest (as many others are saying also)....My series 3 landy must have well over 3 degrees of ??deflection?? especially with new springs on! It's only really a problem when people sling the axles underneath the spring which changes it by about 7 inches in relation to the engine/transmission.....Don't get the twisting into tarmac bit but hey its probably like everything else when you look in detail - a black art....exhaust header lengths and manifold/gas flow designs spring to mind as other dark areas....to the majority of users if it looks about right its probably near as damn it! Just get them as close to paralel as you can, weld em and forget....all will be fine.....HTH Oli.

If it any help, this setup works just fine
Rescued attachment Prop Angle.jpg

Thanks for all the replys , I think i've learnt that unless the extremes of misalignment are present it should not be a major issue and any misalignment shold be kept to a minimum. Keep the line of diff and crank/primary shaft parallel if possible
As nobody is using prop shafts without UJs (i think) Its not a major problem.

Learnt a few things though, great stuff.