240 wagon loud rear vibration at speed

'93 245, loud buzzing/vibration sound, louder with more speed, seems to come from rear. Even louder coasting in neutral or clutch pedal depressed, or just letting off the gas pedal. I just had a good trans/diff shop install (new) TrueTrac and new 4.10 gears, bearings, etc. Noise was the same before this. T5 (Ford) "rebuilt trans" that good trans shop had to rebuild. Clutch and TO bearing are new (2000 miles).

What to check?
-diff - done
-tire balance - done
-alinement - done
-U joints - done (new)

I'm thinking:

- rims are 17" from S60, requiring chunky 2" spacers. Balance wheels WITH spacers on?
-Mustang drive shaft - have specialty shop make sure it's straight and balanced?

What else?

Maybe the parts for the parking brake fell apart and are rattling inside the rotor?

How's the pinion angle?

Are your wheel spacers hub centric ?

Two piece drive shaft or one piece drive shaft? If two piece make sure the two shafts are phased properly.

James M said:

How's the pinion angle?

Click to expand...

^^ This. Mustang drive shaft implies to me that you have a one piece drive line. That takes some work to get the angles correct.