Have a look at the application chart in the post below. If you have a 722.3 / 722.5 trans, might be losing the K2.

722.3 elements and relation


Loss of governor pressure will cause uncommanded down shifts. This was common on GM TH 350 / 400 trans due to governor bore wear. I'm not sure if this is possible on your trans.

There may be a similar problem like this guy.

E320 Downshifting unexpectedly