strange vibration

[shortstack]

Please help....I have a 98 Tourer with 26,000 miles.  When I release the throttle in 3-5 gear and just before the power breaks away there is a pretty strong vibration or "grinding" sound coming from the motor.  it's been happening for about a month or so. Doesn't seem to be effecting the power or anything else. Just my own concern.  Thanks!!!

[Chrisj CMA]

Could be the U-joint or drive shaft splines that go into the pinion cup.  Sounds transfer quickly so its hard to tell where they are coming from, but it sounds like a U-joint to me......easy to check and not too expensive to replace.

[Zorba]

Next time you release it "pull in the clutch" and see if it does it ?
And at what speed are you talking ?

[Ricky-D]

Look hard at the universal joint! If it were to let go, there is a possibility of greater damage than just the universal.  Under strain the universal will run true, but at a mid-point where strain is relieved you will then get a vibration from unbalance in the universal that is being allowed to run in an untrue condition.  This is mainly caused from the universal having to rely on two splines for alignment. The spring help a lot but there is still the engineered sloppiness from the splines.

[shortstack]

Thanks for the help so far guys.....very helpful!!  the sound is happening at speeds from 40mph and up.  I really only notice it right when the throttle is releasing power. 

[Disco]

I have seen final drive problems happen much sooner than u-joint failures.  One local guy changed his at 100,000 mainly because he was replacing a rear tire and was already in there.  It was tired, but could have gone farther.