vibration under freeway acceleration

[mkcman17]

car runs and drives smoothly, esp when just coasting, but there is a perceptible rumble from the back half of the car when accelerating in top gear. if i let off the gas it rides smooth as hell, but even some pedal gives the back end the shakes - just a little. i'm wondering if it's the diff...i put mobil1 synth LS in it a couple months back without friction modifier, but the bottle said it contained them.

any other ideas?

[ak-]

Worn out guibo and or center support bearing. When one fails, the other follows suit quickly.
Worst case could be the drive-shaft.

[mkcman17]

mmmmm guibo looked good when i replaced the tranny 3 mos ago. not sure about the csb though. i DO remember that my tranny mounts aren't exactly solid...

[ak-]

A bad CSB can fuxor your guibo quickly.
I guess it could be tranny mounts as well, but you said you are smooth unless on a good acceleration.

[dkbmxer002]

did the fluid look fine when you changed the fluid? did everything else look good? no shavings or anything?

[mkcman17]

more like ANY acceleration. it's just audible/feelable enough to be perceptible. not a clunking or anything severe, just kind of a low buzzing.

edit: no shavings in the fluid, no noises from the diff either under everyday driving.

another note, when i'm reversing and let in the clutch before i'm stopped/engage while rolling there IS an awful thunk.

[dkbmxer002]

my rear end made a buzzing sound that almost sounded like i had a small zip tie attached to my driveshaft and only did it under load. it got worse and worse till it gave out. but it was only less than an hour of noise before it went. (i was on a road trip heading home)

[mkcman17]

csb's are pretty cheap, so it's probably smart to replace it in the next few weeks anyways. abby, i'll have you take my car for a spin next time i see you.

[ak-]

Alrighty.