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propshaft misalingment


Mack
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This illustrates it quite nicely:

post-10578-004928700 1294178043_thumb.jpg

Front prop on the top, rear on the bottom. Those ones were for my 200Tdi 90

The basic reasoning behind it is due to the universal joint's transmit motion. They don't transmit it in a smooth way when operating at an angle, they start varying the input and output speed in a sine wave sort of way, in other words it speeds up and slows down as the prop rotates. The amount is does this is proportional to the working angle of the joint.

On the rear axle the line of the diff pinion and the line of the transfer box flange are parallel, they're both parallel to the centre line of the vehicle. This means that the two joints are at opposite angles at all times (if we discount other small factors like axle movement under extreme articulation etc.), and the irregularities in speed mentioned above are also equal and opposite and so balance out.

On the front prop the diff pinion is pointed up slightly (have a look! :P) and so the UJ angles are not equal. This would cause an imbalance, so there is a slight mis-alignment in the yokes to account for it and to minimise any vibrations through the drive-train. To try and level out the peaks of the waves, as it were.

It's more complex than I understand, but that's my basic grasp of the concept! :P

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Front diff pinion flange is not contained in the same vertical plane with the Tbox front output flange ( A bit too the right) . In the 110" Puma the rear shaft are also not in "phase". So still not sure is those are 30 or 45º

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Thank you chaps, very helpful indeed! I understand now. What I'm not sure of now is how they get out of line to begin with. Furthermore, because I've got a bit of noise and vibration from my drivetrain I'm now paranoid that my props need realignment :lol:

down to the gearbox/axle alignment, but initial set up is done at the factory/design stage on purpose to eliminate any vibs from drivetrain.

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