What tool for this upper transmission plug?

Brookshire my · 09-09-2025, 03:11 PM

The upper plug on my transmission has this 6 sided plug like it fits a very large allen wrench but it has a round protrusion in the center. What do I need to loosen this up?
Is this a normal plug or something someone cobbled up?

Dave at Pelican Parts · Dave at Pelican Parts's Garage

What is that red seal? Is this a 914 transmission or something that's been swapped in? The angle looks unfamiliar to me.

The stock fastener takes a 17mm Allen (hex) key. Sometimes that gets made with a 17mm bolt and one or two nuts, all tightened up on each other as much as possible. You can get the Allen wrench in various places as well; aircooled VWs used them as well as old Porsches.

Whatever is there in the middle looks like a nut epoxied onto a bolt or a stud; the one on the right just looks mangled.

--DD

Magyar Kiwi · 09-10-2025, 02:43 AM

Hi
I think the red is the edge of a mirror, giving a second view.
That looks rather strange; like someone drilled a hole in the middle of the damaged factory plug and then hammered some sort of plug into the drilled hole?
Presumably after they put some oil in.
Cheers

GregAmy · 09-10-2025, 04:19 AM

A mirror! Of course. I had the same question as Dave...that makes sense.

Man, that thing is borked the eff up. Someone didn't use the right Allen tool and muffed that, then maybe drilled and tapped a bolt into the center? That thing must be seized nice.

And is that some kind of sealant around the stock plug? Below is generally what the plug is supposed to look like, with the obvious hex head for removal.

I'd probably attack that as a broken bolt. Drain the transaxle completely then see if you can get some vicegrips around the edges to get it out. Heat would help a lot. If that fails then a drill/easy out would be the next step (with lots of heat). Failing that, a full drill-out with a very large bit (and heat) and chip away at it.

This is one of those jobs that you're going to simply hate yourself while dealing with it. but when it's done...oh so nice.

We wish you the best, man. Get this done with patience, beer...and heat.

BTW, you can find positive-hex-head plugs to replace these, ones that you'd use a combo wrench to get them off instead of an Allen wench. I installed those on my race car because I'm required to use safety wire on them. I don't recall where I got it but I think it was on late-60s/early-70s 911s? There's also magnetic versions for the drain plug (though most of your regular transaxle wear will be non-ferrous).

Brookshire my · 09-10-2025, 05:21 AM

I wonder if the round protrusion could be where someone drilled into the center of the plug to tap in a magnet and did not get it in far enough to stick out the other side. Or maybe what is left of a snapped off easy out? One way or another it has to come out so I can add fluid.

GregAmy · 12:44 PM

Should be easy to see if that's a magnet with a steel bolt...if it is you might try LIGHTLY tapping it in to see if an 17mm (or even an 18 hammered on) Allen head tool can get an internal grip on it.

I actually thought of a better early-adopter idea if that doesn't work: heat and a chisel and hammer around the edges of the flange of that plug. Be careful not to hit the case itself. (EDIT: actually, after thinking about it a bit more, that would be my first try)

And another top tip: never remove the drain plug until you've verified you can get the fill plug out...short term you might be able to get a fitting in the bottom to pump the necessary minimum quantity (plus some) from under there then quickly install the drain plug.

Plays with cars · Plays with cars's Garage

+1 on Greg's recommendations. I would definitely to at it with a chisel to try and unscrew it. There looks to be sufficient protrusion to get a bite on it.

930cabman · 09-17-2025, 11:05 AM

would DAPO be appropriate here?

looks as though the drain plug was fit here, inside out

How many "mechanics" has this car seen?

Brookshire my · 09-17-2025, 02:16 PM

This morning I finally had a chance to crawl under the 914 and clean the inner part of the plug out and found the center protrusion is actually the head of a tiny rubber plug. Apparently past (lazy) owners decided that rather than fix the plug with a new one it was easier to force transmission fluid thru the tiny hole, I assume with a giant syringe. Must take a long time to fill. I’ll get after a repair when the weather cools down. Here on the Texas Gulf Coast it’s still 95f+ every day. This area leaks a lot and I don’t want to burn anything out. Especially leaks at the rear which I assume is the housing for the tachometer assembly. A proper allen head tool just spins in the opening of the plug.