High speed vibration...any chance its the diff?

diplomaticm3 · Post by **diplomaticm3** » 12 Oct 2020, 12:00

Hi folks...I recently re-installed a new(ish) angle gear and rebuilt driveshaft on my 2000 v70r. The AWD system works great except for a high speed vibration.

I've got new wheels with 65.1mm hub's, new tires, balanced and everything. I have new brakes (rotors/pads) within the last 9 months. The vibration really only coincides with getting AWD back in action.

Is there any chance this vibration has something to do with the rear diff? It's not a huge vibration but noticeable in your seat at 65mph+.

Thanks in advance

Post by **Clemens** » 12 Oct 2020, 13:12

An uneducated guess: a bad prop shaft bearing or missing driveshaft balancing weights.

diplomaticm3 · Post by **diplomaticm3** » 12 Oct 2020, 13:58

Could be...the (brand new rebuilt) prop shaft was making contact with the exhaust. Only for a few days before I maneuverered the exhaust pipe. It looks like I scraped some paint but nothing huge.

Could that really be causing the vibration?

Post by **scot850** » 12 Oct 2020, 14:29

It may not be anything new or re-built that is causing the problems.

There is a bush at the front of the viscous coupling housing under the car that can wear and cause vibration when driving. The other suspect is the VC unit front bearing or the VC unit itself.

The fact that the vibration was not there prior to re-installing the angle gear and prop-shaft may point to the above.

If we look at the re-built parts, who re-built the prop-shaft? Colorado Driveshaft? It could be the shaft is out of balance or an issue with the center support bearing.

Angle gear could also be an issue.

Problem with the system is it is hard to diagnose until you have all that parts. When the prop-shaft is out the rear section of the system is not loaded with any power so although it may ave an issue it may not show up until you load it up with power.

Neil.