Propshaft Vibrations

[Mick02DEF]

Ok so here is my problem:

A little while ago I replaced my front diff flange and seal in my 02 Defender. However, since then I have been getting intense vibrations between 55 and 65 kp/h. It is only at this speed and only under load (in neutral coasting through these speeds it runs smooth as smooth).

It's definitely in the front prop because I've taken it off and driven around in diff lock and again, it runs perfect. I made sure I phased the shaft properly and even played around with the phasing backwards and forwards.

I have a 2in lift, but I put this in 2 yrs ago and never had a problem before I changed the diff flange. I even took it to some Manual Transmission specialists and they had a look and couldn't work it out either.


Any ideas would be much appreciated.

[Hoges]

Can you /did you check the run-out on the new flange? I'm wondering if it might be a fraction off-centre?

[mox]

Did you phase the shaft properly according to the standard way or 45 degrees out according to what has been used on Defenders by Land Rover since maybe mid 90's. Because the pinion shaft on front diff is angled down while transfer box output remains horizontal, when set up the standard way , the second uni would not cancel out the acceleration and deceleration from the first (Note Hardy Spicer type unis are not constant velocity joints.) Seems sometimes this caused vibration problems at certain speeds. Running the unis out of standard phase seems for some reason to reduce the vibration problem. Maybe changes it to higher frequency which does not resonate further.


Almost certainly extra lift would exacerbate vibration. Have not had it with my '97 build Defender 130 at standard height. When I first noticed front unis were out of phase, thought this was some stupid mistake and changed it to the standard format. Then recently when rear uni failed and was replaced, put it back to 45 degrees out. Wonder if this failure was premature partly because of increased torsional vibration load?

[Mick02DEF]

What do you mean run-out and how would I check it?

[Mick02DEF]

I've had it phased in line, 90, 45, 22.5 and they all fail to remedy the situation. If it is only happening under load, would this mean I should be looking for issues toward the gearbox end?

[Hoges]

What do you mean run-out and how would I check it?

There may be a slight (manufacturing) production difference in the drilling of the bolt holes on the new flange with respect to their distance from the centre axis of rotation.

I'd try firstly undoing the four flange bolts at the front and rotating either the prop shaft or the front wheels so that the diff flange and the prop shaft flange rotate 90 degrees with respect to each other. Re-bolt and mark each flange. Try a test run. If no better move them another 90 degrees so that they're 180 deg from the original, mark the flanges again, re-bolt and test. If it's no better then do the same with the rear flange of the front prop shaft.

I had a periodic vibration in my P38 a couple of years ago. Was definitely front prop shaft related. Front passenger seat would visibly shake! I played with the "settings" as described above: it's not perfect but certainly a lot better than it was.

That's all I can think of at this stage other than you might have an issue with one of your UJs which was not previously apparent...

Hope this helps