I replaced the cardan shaft. Did the DIY (easy).
Made sure to align the marks on flange and shaft to neutralize imbalance as much as possible, etc, etc.
After replacement, went for a drive to see if there is any vibration but did not notice anything (I was not getting on the gas alot though).
A few days later, as I was accelerating, at around 3K rpm, I felt subtle vibraion inside the cabin, kind of as if the chassis started to vibrate slightly (it would go away at higher speed or if I let off the gas).
Did this 4 to 6 times and each time was able to reproduce.

My thinking was - hsit, its the shaft.
That same day, in the evening, tried to verify once more what I felt. Got on straight road, got on the gas (decent amount) and was not able to feel any vibration at all.
One thing I noticed was that before the re-verification, I changed the suspension to low and handling to sport (previous was standard suspension and handling at standard).
Decided to switch back to same settings and still was not able to duplicate any vibration.

Now I am stumped. Trying to figure out what the vibration could have been, and why it is not reproducible again.

Wonder is anyone on here had such experience.

 

Road surface material/construction, possibly?

 

that is what I was thinking too.
When doing repro initially, went over road and felt the vibration, attributed to shaft, then drove on the road during day and noticed funny little ripples, which I can see cause vibration when hard accelerating. Went to different road. Was able to repro only once or twice, once in a turn and another in a straight. Just in case decided to crawl under there again.

I just went under there a day ago and undid the bushing bolts, attempted to reset the natural position, and tightened up.
Been trying to reproduce the vibration but cannot so far. The only adjustment made was at one bolt for about 1mm towards rear of car (I marked the locations before loosening bolts to see).

So far good, I will keep trying to repro for next while and will update. Thanks.

 

Nothing new to report. All good here.

 

I just replaced the cardan shaft on mine today because the rubber around the bearing went this weekend. I noticed on the way home that right at 20 mph I am getting a slight vibration and then it goes away. So I will climb under mine and see if I can reset everything better. Hopefully it's just barely off my marks.

 

did you replace the flex disc too? If not, inspect, as failing shaft likely creates cracks in it, necessitating replacement.

 

yes I replaced the flex disc also.

 

I just replaced mine today with the replacement part purchased from www.coloradodriveshaft.com and it works perfectly. The owner told me his will last about as long as the OEM one and is balanced perfectly. I would agree at least with the balance.