[ogrebro]

Had 411 gears put in my 9" rear end. I now have a noise, a rumble and vibration, not under power or completely off the gas pedal. The noise is in the neutral spot when not accelerating or decelerating. I don't remember having this noise before I changed the gears. I suppose there is a possibility that it is a u-joint or an out of balance drive line. I tend to think it is in the rear end, because the drive line and u-joints are new as of approx 3200 miles ago.

Any ideas on what and how to check this?

Many thanks!!!
Bill

[The Flyin Wop]

Having worked on Ford rear for many moons,usually if a "rumble" type noise means soimething is loose or has a crack in it making something move like a cracked carrier support cap.It could be possibly a pinion nut was not properly tighted down,caps,too much backlash or not enough.
A whine woulf indicate a bearing.Did the use the same bearings? Maybe they tighted the pinion down to tight.
That's a guideline,without bein there to hear it,could be anything Dude
Paisano

[cobalt327]

Originally Posted by ogrebro

Had 411 gears put in my 9" rear end. I now have a noise, a rumble and vibration, not under power or completely off the gas pedal. The noise is in the neutral spot when not accelerating or decelerating. I don't remember having this noise before I changed the gears. I suppose there is a possibility that it is a u-joint or an out of balance drive line. I tend to think it is in the rear end, because the drive line and u-joints are new as of approx 3200 miles ago.

Any ideas on what and how to check this?

Many thanks!!!
Bill

The driving condition you are hearing the noise (the neutral spot when not accelerating or decelerating) is called "float". It sounds like a pinion bearing preload problem to me.

You can check the driveshaft phasing to be sure they didn't put it on wrong.

[ogrebro]

Finally figured this out. My pinion angle was too severe about 6 degrees out. Put a 4 degree wedge to tip the pinion up. Still had the noise and rumble but only about 30% of original. Rear u joint was bad. Only about 2k miles but at the severe angle it apparently ate the thing. New u joint and it's nice and quiet.
Thanks for the help!!
Bill