The engines back out sooner than I had hoped..
Fortunately with the front end already off it took <2 hours to get it out. Love how easy the E46 is.
Split the gearbox in search of the leak from the bellhousing and as suspected it was the input shaft seal. I replaced it while the box was out the first time since it was weeping but it was leaking a lot of fluid now and the seal wasn't happy. Couldn't see anything wrong with it, so I tried my luck and tapped it in a bit further. No luck. Had to bite the bullet and remove it and get another one ordered. $60 seal, ouch. I could see the slightest imperfection on the lip of the seal once it was out but have a hard time imagining that was causing the drip, hopefully the next one has no issue otherwise I'm out of ideas. Took a bunch of photos but lost them somehow so here it is removed.
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In the meantime I've reassembled the rear end. subframe and arms in with all new bushings, ball joints, and bearings, 330 diff, 330 rear brakes, new brake lines all round.
330 cluster rings and manual cluster panel panel added. Technically since this is a coupe it should probably have the grey dial faces but I actually prefer the look of the black ones.
The smoke tester arrived, it works good. No complaints except for the smell of the smoke, and it gets everywhere, on your clothes hair, skin etc. I tested with the motor removed and just plugged the purge valve and sucking jet pump but it revealed absolutely zero vacuum leaks. The thing is air tight. Pretty much only leaves a brake booster vacuum leak, bad MAF sensor, or bad O2 sensors, as my rough idle issue. I will have a look at the fuel trims once the motor is back in the car and see what the next step is. Tempted to just order a MAF regardless since it's nice to just rule it out and have a fresh one, I already have O2 sensors on order but they're not due until the end of march.