W115 Starts in Drive. Normal?
 

Normally, that would be a big, fat "no!". But given the ability to push/tow start these old automatic Benzes I have to ask.

It wasn't referenced in the owner's manual but I discovered by accident that mine does, indeed, start in gear.

$150+ for a new one if mine's busted or has been bypassed.

That'll still be a no - your neutral safety starter switch thing should stop the starter from turning unless someone has hot wired it for you.

The being able to tow start these cars is all about the secondary pump that is fitted to these transmissions which lots of other automatic transmissions don't have. The secondary pump runs off a cam system on the output shaft (of the transmission) and is therefore always connected to the rear wheels - turn the rear wheels to build up enough pressure => brake bands and clutches engage according to position of gear selector - you then have a chance of cranking the engine over via the fluid coupling / torque converter.

Thanks for the explanation. Good thing our man Phil is able to do a lot better than $150 (~$83ish from Peach Parts).

My only concern now is to figure out what needs undone and hope they didn't butcher the wiring harness in the process.

I would check that first. If it still starts with the connection removed on the transmission I'd be highly suspicious of a custom wiring job...