M47 5-speed

The plug rounded off when I used a socket. So I ground it down a bit, hammered on an old smaller socket, and it rounded off again.
Tried grinding it to fit a smaller spanner - the spanner broke.
Ground it down further to get two good flats and applied a wrench. The stump snapped off flush with the casing.

The plug seems to be made of extremely hard steel, the most resistant to grinding of anything I have ever encountered. So it is not going to drill out easily, and certainly not in situ.

Is there another way to drain the oil, apart from syphoning with a tube through the filler plug hole, which would be unsatisfactory as leaving most of the debris which is the whole point of draining ?

I tried removing one of the lowest bolts holding the rear cover, hoping it might access the inside, but it doesn't. If I loosen all of the cover bolts, would the cover prise open enough to drain the oil?

Yesterday I gave it one last despairing tap with a small chisel and it suddenly turned as easily as anything. Now it is finger tight, so obviously was not cross-threaded as I had supposed. I'm amazed.

The replacement plug has a cone-shaped seating but no washer. Is that right?

No.

The M47 plug should not be tapered. I was just looking at one and it is definitely the same diameter throughout. This was from my '89 wagon.

There is a copper gasket which, I was surprised to notice, is the same as for the engine oil plug . At least that's what my receipt for these parts from 2005 indicates. I checked and the oil pan gasket fits the gearbox plug, albeit slightly loose. I remember it as being a closer fit. But apparently it is not.

Plug # is 1381498-3 and gasket is 11998-2.
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'80 DL 2 door, '89 DL Wagon

While browsing a chain auto parts store (Advance) for a downpipe test bung plug, I found a rack of plugs (Dorman brand) in blister packs with gaskets and crush rings. Many are in metric sizes, and it looked like quite a variety was carried. I found my M12 plug there too, for the head pipe that came without one.
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Art Benstein near Baltimore

The dead batteries were given out free of charge.

It's a good practice to use a new "crush" washer when re-installing drain plugs. The washer crushes under mild torque and provides a good seal. It also helps prevent over torquing the drain plug, which can lead to RNS (rounded-nut syndrome). My indie mechanic includes crush washers when I buy Mann filters from him. They are also available from many auto parts stores, made of aluminum or copper. The counter guy often gives them away rather than look up SKU #s. I'm guessing the drain plug washers are 18mm.

Chris in NE FL, '94 945 w/164K

I had this issue with the fill plug on an M47 - someone torqued it down because they forgot the copper washer. I also ground the head multiple times until nothing was left. I decided to drive it like that until I could find time to pull the transmission. A couple months later I noticed AFT seeping arount the plug stub threads. I was then able to remove it by rotating it out with a cold chisel.

2 new plugs and copper washers from the dealer and all was well.

The question remains, have you removed the fill plug yet?

You may be faced with the same problem there.

I removed the plugs from the M47 in my wagon by starting them with a chisel. But since I was replacing a clutch, after I discovered they were reluctant to turn, I waited until I had the gearbox out so I could get a good whack at them. You probably won't be able to use this method unless you have the car on a lift. And even then it may be futile. There just isn't enough room to get the chisel at the proper angle.

Had 'em both out again last year and they were no problem that time thanks to anti-sieze compound.
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'80 DL 2 door, '89 DL Wagon

I would use what I call a gear oil sucker to get all the oil out through the fill hole, and fill it up with synthetic gear lube. What I call a gear oil sucker is about the same size as a grease gun. The have a handle to pull a piston up the bore, and a clear plastic tube to insert in the fill hole.

If I decided the get the drain plug out, I'd pull the transmission. I would lay it on it's side, drain plug up. Then I'd find a nut with 7/8" (same as 22mm), and weld through the center of the nut to the damaged drain plug. I'd have my ground clamp on the outside of the nut. After my weld was complete I'd try removing the plug. If it was still stuck I'd hold my welding ground firmly against the bottom of the transmission case adjacent to the drain hole, and do a little welding to the inside of the nut. The welding current flowing through the threads would blow any corrosion out.
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john

I'm amused reading the resourcefulness of you guys on this forum. I don't mean this in a demeaning manner but a compliment to shade tree mechanics across the nation. fat cat

You might try grinding a flat spot into the flush piece and using a screwdriver, but I doubt that is going to work if a pipe wrench broke off.

I suggest heat.

There's an article around here, or on turbobricks about using a big nut (several of them) and a wire-feed welder to build up material, then weld that material to a nut so you can put a wrench on it. The heat should break a lot of chemical bonds and will deform the threads to make them easier to remove - hopefully.

If you weld on the car, unplug your ECU's!

Uh.... now that I think about it though, that article was about removing bolts from the head - aluminum won't weld to steel, but steel will weld to other iron-based alloys at least somewhat. My parents mechanic was able to weld a bolt onto a stripped head. I think both the pan and bolt were steel and the results were all right. Just don't heat the bolt past cherry red when welding.

Good Luck!

You'll want to do more than unplug the ECU. If you weld to the transmission drain plug, the grounding electrode must be adjacent to the broken drain plug being welded. If this isn't done, the electric current can flow through ball and roller bearings as well as bushings. They'll be toast if that happens.

With the welding ground in the right place, I wouldn't bother to unplug the ECU and EZK, but it can't hurt.
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john

John,


Did you know that the magnetic component of the welding current can radiate past the ground electrode and through the ferrous structures? With some sensitive semiconductors, this can be enough to destroy the delicate junctions. The magnetic field can induce high local voltages in the lengthy harness, just like a radio antenna. You and I know what is at the other end of that long and many conductored harness :)


Goatman

Yes, I know that.

The amazing thing is the repairs body shops make without disconnecting things. I'm sure they must toast a component sometime, but you sure don't hear about it much.

On the other hand, I sure toasted the transistors in a Dana Perfect Cruise Control while testing the vacuum pump and vent solenoid one day. I forgot to disconnect the plug in at the cruise control electronic box when I applied voltage to the vacuum pump and then the vent solenoid. I tried to bu the two bad transistors, but it turned out Dana buys enough transistors to get their own part numbers on them, and there was no cross reference.
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john

:-O Thank you! I didn't think about that at all! Easy way to ruin a transmission in a hurry. What about clamping it to the fill bolt?

-William
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1990 740 Turbo, on its way to stock specs, maybe beyond

Clamping the ground to the fill bolt is probably okay. The current shouldn't flow through bearings there.

Like I wrote in another response to this thread, consider pulling the transmission.
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john

I keep seeing posts like this and wondering.
Are later model drain plugs a different design, do they just tighten them too tight,
or what?
I never had problems like that on the oldtimers!

I've had trouble with some of the later transmission drain plugs, too. The late drain plugs have a reduced size hex head, 13mm instead of 22mm, on the same size plug. The problem is worse with the cast aluminum case transmissions where evidently there is a little dissimilar metal corrosion. You must be careful not to tighten the 13mm head drain plugs very tight, or they won't want to come back out in a few years.

When removing one of these drain plugs, you must start out with the correct size (13mm)six point box end wrench. Even six point sockets have a little tendency to tip off the head of the drain plug. Once the 13mm hex head is damaged, you've got big trouble.
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john

I had this happen on a not-Volvo and decided I had to get it out for worry that it would come out on it's own, probably miles from home.

It was hard steel but not as bad as you describe. I drilled, drained, heated, removed the shell. Did a little damage but it resealed OK.

But: Mine was just frozen and stripped, not broken off flush.
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240s: 2 drivers and some parts cars

If you crack lose all teh bolts on teh rear housing, There is a Square hole behind teh housing that will let oil drain BUT it is not the lowest pint in the trani so your hopes of getting any metal particles to drain are no better the siphoning out the Fill. Not to mention , I bet it messes up the gasket.
My housing gasket was trashed when I took the back end off to replace the Shifter Rod seal
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'75 Jeep CJ5 345Hp ChevyPwrd, two motorcycles, '85 Pickup: The '89 Volvo is the newest vehicle I own. it wasn't Volvos safety , it was Longevity that sold me http://home.lyse.net/brox/TonyPage4.html

Many thanks for that information. It's as I half-guessed, it's not the lowest point therefore doesn't actually offer a solution.

So it looks like syphoning or a suction device.


I think the reason later plugs seize is partly the heads are smaller, so you can't apply as much force, but also they have a flange like a kind of one-piece washer, and this too creates friction and a place where corrosion can bind.
I've had problems elsewhere removing bolts that have this feature. Older designs using traditional separate washers were much better.

I put a little anti-seize compound on the threads, and a little more on the flange.
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john

After reading all this and seeing what seems to be very helpful answers, I thought I'd just put in my 2 cents-if all else fails-drill a 1/2" hole into the drain plug-pack it with a few ounces of C4 and give it a "shock". (How do you set off C4 anyway?) That drain plug will never bother you again.

C-4 takes either blasting caps or electrical current. I don't know which :D
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1990 740 Turbo, on its way to stock specs, maybe beyond