Hey everyone, kind of a long post. But, I've searched for an explanation but haven't been able to find an answer. I recently got a 2007 P71 current miles are 146,348. While driving I lost over drive. I dropped the pan, than the valve body and found the servo and a full unbroken snap ring sitting on top. Thought it was strange so I inspected the snap ring groove and it appeared to be fine. While the valve body was out, I thoroughly cleaned it, installed new check balls and verified that all valves were moving and free. I got the OD band pushed up, and installed servo and new snap ring, making sure the band and servo had engaged. Reinstalled valve body and torqued it all down. Installed new filter and oil, and out for a test drive I went. Same issue, no overdrive. Thinking I didn't do something correctly I tore everything back apart, servo and band are still seated correctly, reinstalled everything and same thing. I'm thinking there's more wrong then just the servo, and I may need a rebuild. But before I go that route I wanted to see if anyone had any suggestions.

When you reinstalled the servo piston, did you make sure the pin was properly engaged into the o/d band?

I apologize for the late reply. As far as I could tell the O/D servo did engage the band correctly. I pushed the band up as far as it would go and held it there and installed the servo. Checked through the peep hole and saw the band hadn't fallen back down.

You said you cleaned the valve body. Are you sure there were no pieces of the broken snap ring in the OD valve? That would prevent the valve from opening the circuit. No movement of the OD piston.
Does it not try to engage the OD at all, or does it shift into OD and slip?

Yeah, I took the valve body apart and cleaned it really well. The snap ring was not broken at all. I know I've seen where people that they weren't but it was just the end piece that had broken off etc. I moved each valve with with pick and they seemed to move easily. I did drive it last night and as it went into OD, it went to neutral like it has been doing. I decided to Rev it up to see what it would do and it did slam into OD sped up and then kicked back into what felt like neutral. No OD flashing lights so at this point I'm certain it'll need a rebuild.