Ok.

check your gear teeth. I have found a little piece of metal stuck in the gears that I needed to pick out with a tooth-pick. I have found this more then once through the years of building Associated gear diffs. Its the first thing I check when building a new diff.

It’s more then an extra hole look at the pic the arm has one big oval hole in it for an insert with a hole in it so to change shock position u change the insert. This means more shock angle possibilities and a stronger arm and it will cost less for them to update the arm with new shock locations. Prett6 trick little idea there

I have about 5 days at the track with my new b6d. I couple weeks a go I had asked, about front arms being tight and are not freely moving. The consensus was to let them break in. One arm feels good and did the day I built the kit. The other arm however is still just as tight as before. Without the brace everything moves freely, so I assume it doesn't have anything to do with the pins or holes. I tried a new arm from a spare I ordered and it's also tight. I got my calipers out and it looks like the bulkhead with brace is .2mm bigger than the opening of the arm. 19.7mm bulkhead with brace and 19.4mm-19.5mm opening in arm. Brace is 1.5mm and bulkhead 18.2mm. Where do I go from here? Does anyone have this issue or measurements for comparison? Are there more precision parts/upgrades? I run 17.5 stock class.

Thats a good thought, thanks. To be honest Im not impressed as I was with my B64. I think Ive also got a bent chasis. With the shocks adjusted equally for droop, Ive got about 7mm more droop on one side at the front and the same on the opposite rear corner.

It's a buggy not a touring car. Take off a little bit till it moves freely and live with it. A little tolerance is needed anyway.

Arm reamer should do the trick

Are you spinning the motor by chance when checking the diff? Maybe just feeling motor cog..
Another test, take diff case out of car, just feel diff then. Perhaps you are crushing the diff case with overtightened screws

Going to run my b6 carpet car next week on high bite clay. I bought the ball diff and willget that swapped out. Trying to decide what else to change? Anyone happen to have (or see) a setup sheet for the carpet car (gullwing arms) on dirt? Wondering about different spring cups and all that?

Lots of guys run gullwing on dirt. I think you'll find most of the pro setups call for that.

I'd guess the biggest changes will be ride height and roll center.

I run my B6 on high bite clay (running slicks). Im running Yokomo green performer spring front (YOKRP-083G) and green rear (YOKYAS-1050) with RCSS 3x1.4+1.0 pistons front and rear with 30wt oil front and rear and its pretty dialed. Any setup you can find from this year SDRC Top Gun shootout will get you started in the right direction since that track was super high bite.

Does Associated use metric or standard hardware?

Metric hardware

I run gullwing on carpet, clay, and dirt. It just suits my driving style. Different springs of course, the looser the surface the lighter the oil and springs to get traction. I would just ask the local fast guy what that person is running to take out a lot of guess work and experimentation.... you can save more money doing that.

Wouldn’t you want to stay with the gear diff on high bite clay?