Quoting a couple things from earlier in the thread...
Originally Posted by Kaos22B
For clarification, the stock mount will "work". As in the car will drive. The issue I found was that when getting into first or reverse I had lots of shuddering and clunking from the rear diff. Initially I thought it was my clutch but after narrowing the clunk down to the diff, I looked up the part number, saw it was different and ordered/installed it. In the short trip from one shop to the body shop for other work, I had no clunks. I will do more testing after the car returns.
Originally Posted by NSFW
I used the R160 mount. You can tell because unlike the diff itself, the crossmember looks exactly as dirty as the stuff around it:
I had some klunks when turning sharp corners and accelerating, but those went away when I added LSD juice to the Extra-S in the diff. I still get some klunks when drag racing but not as much. So I wonder if switching mounts would get rid of the last of my klunks.
The first time I launched, I was sure I'd blown an axle or three. Vrooom-screeech-BAM-BAM-BAM-BAM-BAM! By the time "holy shit was that an axle?" went through my mind, I was in 2nd gear and still pulling hard, so I kept going. I asked my girlfriend to watch for wheel-hop and she said there was none, so I figure it's the diff banging into something. Or maybe the transmission itself, but it sounds like it's coming from the back of the car.
Originally Posted by Scooby2.5
Mine looked just exactly like this and it was a new one for a spec B.
Spec B rear diff mount part number is
A couple months ago I started getting clunk noises every time I started from a stop.
Based on the posts above, I ordered the spec B rear diff mount, and I put it in last weekend, and it fixed the clunk noises. I gave it a couple of hard
launches this evening and those were clunk free as well. EDIT: The clunks came back after a a while. I'm not sure exactly where they're coming from.
Huge thanks to Citka for all the help with the installation, by the way!
The stock diff bracket just barely contacts the underside of the diff, basically right in the center, between those two bolts that come out on the bottom. The spec B mount has a slightly wider and deeper notch around the 'spine' on the underside of the differential, so there is no contact, and no noise. I think that when I first installed the R160 bracket, the fit was tight enough that nothing moved around except when launching hard. But after enough of that abuse, some play developed, and every time the diff moved it would clunk.
Bracket flex might have been a factor as well, as the R180 mount seems quite a bit stiffer around those two bolts on the underside - it's very stout piece of metal.
I'm going to update the first post to point to this one, since between the three of us we've now got confirmed documentation about which part to use, and why.