A4LD, lost overdrive today

[Eddie94]

Was driving home on my lunch today and it thumped out of gear while I was in Overdrive, and now will not engage at all while the shifter is in the O slot, engine revs and I hear a whirling noise. Upon moving the shifter to the D, 2, or 1 from the O slot the transmission still doesn't engage, but after shifting to park, I can then shift straight to D, bypassing Overdrive, and it drives fine through the first three gears.

I've spent most of my spare time today since I lost it searching these forums, and from what I've gleaned it could be:

1) overdrive band
2) vacuum modulator, or the line running to it
3) valve body
...4) governor?

(fluid and filter were changed out a couple months ago; couple thousand miles have been driven since service with no issue, double checked fluid level and its tip-top)

I understand most things automotive, but transmissions are my Achilles' heel, so I want to check and make sure I'm not bumbling down any wrong tracks, and not missing any important ones. Is there one of these that is most likely? Do I have the 1-2-3-4 order of likeliness down right?

Here is a picture of my pride and joy, to tug at the heartstrings ><

 

[Gadget X]

I'm not sure why it wouldn't go into gear from park to OD setting, but I do know that the 3-4 shift and the tcc lockup are controlled by solenoids on the front passenger side of the valve body, that you have to drop the valve body to replace. There's also a possibility that the z-link could be bent or otherwise misaligned. Sounds like you're having issues similar to mine at the moment, I just haven't had the time to do anything about mine yet. Must be something in the air! Good luck with it!

 

[BrooklynBay]

Connect a 0 - 300 PSI test gauge to the port on the rear driver's side of the transmission, and check the pressure in each gear range. You might have a misadjusted shift cable or a bent Z link as previously stated.