Ok.. a friend of mine just had a SC IV installed by a very good transmission guy locally. The tranny guy had one questoion about the Allison internals that he could not figure out, so I told him I would post the question here and see if we could get him an answer.

What is the hole for in the C1/C2 housing (I think I got that right :))

He was saying that he thought this hole would cause pressure loss.

Thanks
Lynn

Never seen one before i guess oil hole. dave

http://www.atsdiesel.com/PDF/TriplePack_ver.2.0_A6-med.pdf

step 26

That hole is for bleed off pressure. The trans guy is correct in as that it will lose pressure, but incorrect in stating that it could be a problem. We want to dump fluid at certain times.
mike

Not being an expert I'd have to say that the hole's there for a reason. I'd also have to believe that Transgo would have (or perhps they already have) handled the hole issue in there Shift Kit.