Driveline roar on decel (long)

[climo]

I just developed a loud noise coming from the rear driveline when I decel. If I go over 45 in 4th gear and let off the throttle (normal cruising range) I get a nasty roar sound out of the driveline area. If I apply slight throttle it goes away. Let off and you get noise. Third is the same way. Really annoying.

Now here are some things I've done before this started. 1. Driveshaft was completely rebuilt due to a bad trans yoke needle bearing. ---> I drove it around a few days waiting on my engine mounts. No driveline noise or vibration present.

2. I replaced the engine mounts because they were over due. Factory nissan. ---> Now I get the decel roar out of the driveline. Only when I let off the throttle.

So, now I think out of balance driveshaft some how. I drive back to the shop and take the manager for a ride. He agrees and rebalances it. Even shows me to verify. They re-install it and I go home. Still no change, roars on decel.

Sorry for the long post. It's hard to describe. Anyone have any ideas? I checked the diff and it seems ok. Trans output shaft seems tight. It just started once I replaced the two items.

I forgot one item. My engine has a numbing vibration starting at 3k and up. With the old engine mounts the vibe was tranmitted to the cabin where you could feel it. Now with the new mounts it smoother in the cabin but now I think the vibe is being transmitted to the driveshaft instead of being absorbed by the chassis. I'm tempted to re-install the old mounts to see. Ideas?

[NISTECH]

check your trans mount and diff mounts. sounds like one of them is worn out.

[climo]

I should of added that the trans mount has been changed with the nismo transmission mount. The only other one is the diff bushings but they seem ok. When I grab the diff and shake it it doesn't move. Maybe their too rigid?

Can the diff bushings be replaced easily or does it require removing it from the vehicle?

[Nathan]

When my car did something similar, the front diff bushings had ripped TOTALLY out and the driveshaft/diff nose was rubbing the rear sway bar on decel. It was nasty I tell ya.

[climo]

Nathan, how did you fix the problem? Did you install new diff bushings? If so how tough was it to replace them? Mine look ok but I'm not sure.