I replaced it with a used one. I got lucky up here, it showed up on Craigslist a few days after mine died.
I still have the transmission that died. I removed the bell housing and found damage behind the front pump, three distorted Philips head screws (2 in the pan); the splines on the front planetary were stripped.
Link to new thread with the pictures of damage-
722.117 Failure mode
The pan was surprisingly clean, I theorize a PO had some work done on it, but the Philips screws had NOT been installed with Loctite. I do not know if they were part of the failure or the splines in the planetary would have stripped or not.
I am going to replace the front planetary along with the damaged parts with good used parts. It's somewhere on the "long list"! The bell housing gasket along with the front pump seal should be replaced at the same time.
I have a recent quote from some Mercedes dismantlers in Glendale, Oregon at $100 for the entire bell housing assembly; I am not certain whether this includes the front planetary set but it would certainly cost a lot less to ship the parts rather than a whole transmission.
I will go out and pull that bell housing again and take pics of the damage I found inside.
If you drain the fluid and the pan is full of wear debris it will probably need more than what I have mentioned. But since these transmissions are no longer being made, consider the repair!
Once again, if this is the front planetary, it should be repairable; if so, ordering just the parts needed would be cheaper than shipping an entire transmission.
In my case I was fortunate to find an intact replacement, drove to their shop, threw the replacement in the trunk, went home and installed it.
And YES you should wear PPE when checking for pressure- face shield, gloves- crack the line just enough to see if it will spray. Dripping doesn't count.
Cheers,
snapped_bolt