My 2003 disco ii with 930000 miles is at it again. It did this a while ago then stopped.
When I reach 25mhp, and up to about 45mph, I get this horrible shake in my drivetrain. It does not go away as I go faster but it does smooth out to a steady vibration. If Im in park and rev up the engine it does not do it, but if I am at 40mph and put it in N to coast it will continue. It can be worse on one leg of a trip than another. I just cannot seem to narrow down the location. No signs of cracking on my propshaft, cv boots are all in tact, no visible crack or leakage from the front diff (but ill be opening that up tonight just to be sure). Im at a loss.
Yes it does still have the Rotoflex propshat in it. I check that everytime I crawl underneath it, and as of now no signs of wear.And when I sy vibrationit makes the change in my cupholder jingle.

 

If it doesn't go away in neutral, I'd probably lean towards wheels or tires and not drivetrain.

 

You think something like them beng out of balance? I have not run over or hit anything. Ill get under it in a few to see if I can find where a weight was lost. It has a mechanical grinding frrl too it though. Im not ruling out your suggestion Ill deff take a look that way. It is still tracking true so they are in alignment. The roads in my area suck though since our highway engineers felt allof our roads needed NASCAR inspired slants for rain drainage.

 

re: highway engineers

And I'll bet a bunch of them came from North Avenue Trade School in Atlanta, you can tell by the old gold and white stripes they paint down the center of the roads...

 

So, has your front drive shaft been rebuilt or replaced yet, when did you last check your rotoflex and when did you last lube your drive shafts 6 fittings?

 

just a thought, feel along your tires for cupping? I had this on my toyota camry certain speeds would cause the car to shake like crazy.. Feel along your tires do you feel large valleys? I would def check into what Mike is saying but also could be something simple like tires.

 

I would think the easiest/quickest thing to do is rotate your tires front to rear,
if the vibration moves from your wheel to your seat or increases the problem is with your tires.
If it does not time to look elsewhere.

 

Mike, I looked at it again last night in an attempt to locate any fittings but found none.

 

As fast as rebuilt/replace I can't say. I bought it at about 60000 miles and have not done it myself.

 

I had the same problem and went crazy looking for a solution. Replaced drive shafts and rotated/balanced tires. In some degree it was always there between 45 - 50 mph.

I recently replaced my wheels and tires and it went away.