Greetings, I have noticed a vibration develop and increasingly get worse. It is most noticable when i am accelerating. It is like a frequency vibrations, it slowly builds up, then back down the back up, like a wave. it feels like it is coming from the rear end. any ideas what could cause this. thank you

 

is there anything i should notice on the u joints or just replace them?

 

Its probably U-joint especially if it was fine a while ago.

You can press up/ down / left /right on the drive shaft near the Ujoints and see if they wiggle at all when you press on the driveshaft...If they do you'll know they are bad.

If replacing them dont help and tire balance dont help...it could be a bent axle.
I had a bent axle but it didnt generate a pulse. Start at the Ujoints and go from there.

-Gun

 

As previously states...U joints.

 

Check all the things previously mentioned PLUS:

o Look at the driveshaft closely for any dents or signs of it being bent.
o Check your motor mounts and more importantly the transmission mount to make sure it's not going metal to metal. This will not CREATE a vibration, but it will greatly amplify a vibration that with good motor mounts may very well be no trouble at all.

 

That's a pretty vague description. What speed does it come in at and go away at? As everyone else has said....U-joints. They will vibrate like clock work though. They come in right at 35 and usually smooth back out around 40. To check them, I would take the tension off the driveshaft. Park on level ground or even take the rear wheels off the ground. I would twist the driveshaft, not push it up and down...and look for play.