Originally posted by roger blose
I have a '96 4.6l T-Bird with 120k that has developed a groaning vibration in the drive train at between 30 and 50 mph. I replaced the differential bushing and it made a slight improvement. I am thinking u-joints or tranny outputshaft bushing may be shot. The car is fine at highway speeds and I do not want to begin replacing more parts without cause. I also get a clunk on coast down, downshifts which is coming from the tranny tail / floor area. Anyone had a simular situation and possible fix?
you've EXACTLY described the symptoms I'm having with my 97 bird (4.6L, 93k miles)
I have both things you've described:
1) groaning vibration, goes away after 50-55 mph. this seems to have "speed-pockets" when it comes on: first betw.30-35 mph, then at 45 mph, then slowly fades with incresed speed. I feel it in the st.wheel, and on the whole frame of the car,too.
2) clunks on downshifts/when letting ff gas sometimes from the tranny-tunnel/ under the floor where the tranny is...exactly:
just like you, i replaced the IRS oem diff-bushings TODAY, the vibe is that I felt in the seat/floor is gone, but the groaning noise is there, although less intense. the ride feels a lot smoother and tighter;
and the clunk is very soft now, not so loud; improved, but still there a bit.
next step for me is: U-joints
then: tranny mount/motor mounts(they're not totally gone, but not in best shape either, and this "groaning" type of noise/vibe can very well come from engine/tranny mounts being bad, IMO. )
However, as we both can see, the IRS diff-bushings also contribute(d) to this...
with new u-joints(IF they're bad), tranny/engine mounts(the BIGGEST contributor, I think) this should be gone...hopefully.
what are your planned modes of attack against this "groaning" ?