Torque converter drain plug stripped!
 

Why in God's name did they make that thing a tiny little 5mm allen screw?! Anyway, I'm going to try the hammer and chisel method next, but wanted to ask a question first. I PM'd someone about this who thought the plug thread might be a reverse thread. Can anyone verify whether or not the thread is reversed? I was trying to get it off counter-clockwise as though it was a normal thread.

Another question: If I decide to blow off the TC draining, is it okay if I mix standard Dex/Merc V fluid with a synthetic fluid like Mobil 1. I think the fluid I have in there now is Valvoline Max Life, which is compatible with Dex/Merc V. And the fluid I bought to refill with is Mobil 1 synthetic.

The fluids are compatible.

The plug is a normal right-hand thread.

CAVEAT - I've done this successfully on GM, Mopar and Toyota transmissions. I don't know if it works on MB transmissions.

If you can't get the TC plug out or if there is a risk of not being able to get it back in place, flush the fluid with the engine idling. Disconnect the transmission cooler return line at the radiator, start the engine, pour fresh fluid through the dipstick tube as dirty fluid is purged from the cooler line. Keep going until clean fluid comes through. Do this after replacing the filter.

Sixto
87 300D

Thanks for the ideas. I just installed the new filter and put the pan back on. I'm going to take a break from this for a while and mull it over. My filter was crusted with crap, the pan had sludge and lots of particles, the fluid was dark and murky. Not good. I'd really like to get that nasty fluid out of the torque converter. I may go so far as to drill out the screw and replace it with one that has a hex head instead of that ridiculous 5mm allen head.

I've had great luck using left hand drill bits. The damaged item using comes out before I get a hole big enough to insert an extractor.

A RH bit may just make it tighter or drop it on the other side.

Is there room to try one of those external type Ez-outs? I believe at leat 2 Members have said the used them on Allen Head bolts.
I bought a set but have not had a chance to try them on anything yet.

I stripped a drain plug on the transmission pan of our project SD, so I grabbed the edges with vice grips and turned, broke it loose easily. Not sure if that tool would fit into the space by the torque converter....

You can try a Torx bit on the drain plug. Get a set so you can try different sizes. Get a new drain plug first and then have a go at it.