I think it was only plastic on 06-07 h3's, 08 and later got metal forks I believe.
Not true. I have seen several 08 (including mine) with plastic shift forks. In fact...I cannot find ANY proof that GM ever offered a metal fork for the BW3393/3394. All GM forks I have been able to find are plastic. The aluminum replacement fork that so many refer to is aftermarket (made by Dorman), and I suspect many cases have been rebuilt at the dealer using the Dorman fork. Perhaps the factory eventually started outsourcing the Dorman fork at the assembly plant? Whatever the case...the alum. fork is clearly a better piece, regardless of where it comes from. The case in the photos already has an aluminum fork but, for $20...I would replace it due to the wear on the shift pin (look closely at the fork photo).
MORE INFO:
*Early cases had the fill plug located too low, and this causes an oil starvation problem. So if you have an early case...fill it from the speed sensor hole.
*The Alpha cases are slightly different for the exhaust routing...but it is very minor and has no effect on internals.
*Later cases have the internal snubber added to control chain-slap. This snubber likes to get loose, flop around inside, and cause havoc on the internals. (The one pictured here is an early case and does not have the snubber).
*Even though there are many different part numbers...all H3 t-cases interchange with all H3's. This includes 4:1/2:1 versions, V8's/L5's, and sticks/automatics. However, I do not know if the gearsets can be swapped between the 3393 (2:1) and the 3394 (4:1). I would think this is possible but, you must use all the matching ratio's parts. I doubt if the cases themselves are any different between the two versions.
*Download the GM rebuild instructions from Schwarttzy...very helpful.
*Definitely install a new chain and a metal shift fork. The chain is directional, and must be installed in the correct direction.
*Pay close attention to the planetary gears when you re-assemble it. They must indexed to the proper location, or the case will bind in 4HI-Street. There are marks on the planetary gears that must be aligned with marks on the sun-gear (look closely at the planetary photo)
*Lastly...the BW3393/3394 case is magnesium (not aluminum). It is very soft and reacts with dissimilar metals, so use sealant on the case bolts, speed sensor, and encoder motor where they come into contact with the case. This will prevent them from corroding and fusing themselves to the case. Go easy on torquing the bolts of the case-halves...they're easy to strip...15 ft-lbs is plenty.
