Stripped the hex fill plug.
 

Tried to replace my my 6MT gearbox fluid today.
I only had to remove the 3rd belly pan only to get access to the gearbox.
Tried to remove fill plug but stripped out the hole.

Fill plug is in a tight location, on the passenger side with the frame blocking access.
I could barely just get a ratchet head up in there.

I'll have to take it to a shop and have them remove it.
I figure they could try to use a chisel method or a weld nut method.
Both will be hard, since there is very little clearance on the side of the gearbox.

At least you had the foresight of loosening the fill plug BEFORE removing the drain plug. Could have been a worse day than it was...

Stripped the hex fill plug.
 

It's a fairly large hex correct? I would try to find a torx that needs to be pounded in (since likely no room to swing, prob need to use a lever to press it to in.

Work it around in circles (eg push at 12,3.6.9.12 o'clock). This method often works. You are basically broaching a star shaped hole.

Ideally you would cut a concave dent at the end of the torx to help pull the chips into the center.

Best if you can start with one size and bump up to another. Eg T43 then T45.

For a normal hex bolt I do the same idea but I use spline hex sockets.

I don't think that will ever happen again.
100% of threads and videos include this tip like it's biblical advice.

8mm

I actually thought you said drain plug. 8mm will be easier to find a torx that will broach it's way in. You probably don't have room to drill for a screw extractor.

- BEST is to abandon the project bc your X3 has low miles.
I also know a lot of BMW owners with MT > 200K miles on stock fluid.
Leave the stock fluid alone.
At time of clutch job, deal with this issue later.

- Most people who strip this fill plug bc:
1. The hex key or socket is not fully inserted, either from dirt inside the recess area.
2. The area is not heated beforehand. Remember that over time, salt etc. collects there causing corrosion. I always heat that are a bit, maybe 30-45 sec of propane torch.
3. Another trick is to tighten it a bit (yes tighten it), then loosen it right away.
Somehow the force of tightening "breaks" the bind, then once you loosen it it is easy.


Below is a video on a VW Passat with stripped fill plug, it is a NASTY job.
So again, abandon the job and walk away.
Don't let your ego dictate the solution lol...


https://www.youtube.com/watch?v=gUlUY0xmuqA

No way room for an extractor.
Photo is deceptive, since you can't see the depth.
Entire gearbox is housed in a cavity on the passenger side.

Good advice cn90.
I already gave up.
I will call a few shops this week and see if anyone wants to take a look.
I want to change the fluid, but will let a pro handle it.

Not even an option on the X3.
Fill plug is next to a frame rail thingy.
At best, maybe they weld a hex socket in there.
No way extractor.