[G.R.]

I had a bad ring gear in my SPF--car always had a bit of vibration, since new.
In May it began to make noise(only around 1200mi on it)--whine and squeal, when downshifting and/or rolling out, vibration seemed to worsen--eventually it started to make noise/vibration under acceleration also--my mechanic checked everything and eventually we pulled the rearend--this was unfortunantely just a bad "from the factory" rearend--the ring gear looked like it had been run through a grinder and after a dye test was done there were 3 hairline cracks in the gear--
Had the Diff completeley rebuilt--and from the very first day I picked it back up it has been as tight and quite with no vibration or noise--even under hard acceleration/deceleration

FWIW