help needed with 904

Ok new day. really would love to know what I'm fixing? Thinking out loud here: why is this transmission that was rebuilt lose reverse? This very well could be just a bad lip seal on the reverse servo, and why some replace that servo with a billet unit. (sometimes the OE servo cracks or flips sideways making reverse go away)
Why is the oil so dark? Why is it That the reverse 4th clutch packs (have not pulled them apart yet though) okay and the one/two clutch packs are all dried out and burnt looking? The direct clutch pack drives almost everything in the trans, and is the one that usually burns up. AND the fluid burns from the heat of the clutch pack slipping. Why is it when I put air to the apply reverse it didn't make a clicking sound just more of a wishing through sound? Again, probably a bad seal on the reverse servo piston.(they also crack and allow fluid through instead of holding the band tight like it should.) And for some reason when I pulled the pump off the front it seems like there wasn't a gasket there like there should be? There should be a gasket, and it's dark like the pump casting, so you may have just missed seeing it. Now I start to wonder if the person who rebuilt this last time miss something? Like is something just messed up in the valve body also to make this other stuff happen? Or is the pump bad and not giving it enough fluid?
It's possible, but very unlikely that the VB caused this.
The pump is pretty easy to see damage on, so a visual inspection usually points out any pump issue's.
That is also why they put pressure test ports all over the outside of the trans, so a person can verify pressures to each function of the trans.
Some rebuild a trans and forget to blow out their cooler lines so it get's contaminated again right away.

Remember the motor was all plugged up and he was having major overheating problems. Just wanted to make sure that I don't go through all this just to have the same problem LOL