Diff drain plug - help needed

[s class]

Well I need more than help, I need a miracle......

On pompy's 450SE, he asked that 'while I was at it', please could we change the diff oil. 

I know that these diff drain plugs can be very difficult to open - its a 14mm in-hex plug, and quite shallow at that.  I had no joy with a long pipe extension on my breaker bar - in fact I could see that I was starting to round out the plug.  I decided that an impact wrench might be the go. I bought a serious air powered one capable of 315Nm, and still, I have had no joy.  I tried applying a pre-load torque with a breaker bar and pipe in combination with the impact wrench, and the inevitable happened - the plug is beautifully rounded out. 

I guess I could drill it and take it out in pieces, but I think I would then need to open the back of the diff to ensure I'd got all the shavings out.

Help!

[koan]

I've tried to get a couple out, no joy.

I ended up taking off the rear mount and back cover. You can then inspect the works, and go to town on the plug if you wish.

koan

[s class]

Its just frustrating when a 1 hour job becomes a 1 - 2 day exercise.  At least I'm not the only one that's struggled with these.

[TJ 450]

Autsch!

I never took my drain plug out, for that very reason. I drained it by removing the rear cover, when I felt I was just going to round it out, just like Koan did.

The rear cover can be removed without too much difficulty.

Tim

[s class]

I managed to open the fill plug without too much misery, so yes, I could just open the back plate to get the oil out.  However, the drain plug looks so nasty now I feel obligated to remedy the situation. 

[SELfor50]

I've done a couple of these now, and it seems - luckily, they've all been fine.  Maybe just an extension breaker bar and they come good.

It's a shyte situation - you could try and remedy, but may end up having to swapout the whole diff housing then?!

I reckon drain it from the back and leave as is.  Then wait for a cheap diff to come up or even a wreck to salvage one.


The first diff swap I did, the drain plug was fine.  But when we swapped out the 450 for a 280 diff, the 280 diff didn't have a crush nut on the front of the diff... so reverse away from the hoist 15-20mtrs.. and pinion nut etc falls inside diff.. locks up and took about 2hours to get the car back to the hoist to swap back.  Totally f*$ked when a simple job takes days to remedy.   

[WGB]

I still have this old tool which was part of my 220S Ponton's toolkit (which I kept after I sold it in 1974).



It fits perfectly and has the correct angle to clear everything but from memory it still needed a hammer or a pipe extension to undo my drain plug nut.

The diff appears wet due to being sprayed with degreaser.

It is not hard to remove the the rear diff housing or else if the filler plug removes more easily use a suction device.

Bill

[s class]

Thanks Bill.

I think part of my problem is not having a hoist.  I'm working with the car on jack stands, and then there really isn't much room to operate with a pipe extention on a breaker bar - the available space is jut enough to take up the slack and bow the pipe...

[KenM]

Obviously this is of little comfort now, but we get blanking plugs similar to this that need to be removed on large air con compressors, which are big lumps of cast iron and the plugs often just have a 1/2" square drive female port. A decent blast with the oxy torch around the plug is necessary to expand the casting otherwise you're guaranteed of shearing your 1/2" drive ratchet or extension, there's just not enough area to transfer enough torque to the plug to move it otherwise.
Sorry I've got no tips to help the current situation though.

Ken

[David]

The only solution now is hamer and chissel on the collar. Try a fairly sharp chissel to make the initial notch, if possible at 6, 9, 12 and 3 o'clock. Then a not so sharp chissel, sharp solid raps with the hammer. The impact normally does the trick. The heating up with a torch may also help to break the bind. Follow that up with penetration oil. Then the chissel. Best of luck.

[s class]

The plug is out.

I dropped the diff off the chassis, and opened the back.  Good news is its in pristine order inside. 

I drilled through the plug, and enlarged to about 12mm.  I used a grinding stone on a dremel to slowly work the hole up towards the threads.  When I had just just touched the threads, the plug fractionally collapsed in on itself, and I could use the chisel trick to drive it anticlockwise with not too much trouble.

I collect the new plug from the main dealer tomorrow - they're not expensie - like about $2.50. 

[pompy]

S class, how much is that perished rubber you were talking about...?

[TJ 450]

Nice work... Fortunately, removal of the rear cover isn't too bad. Removing the whole unit is a different story.

Tim

[s class]

pompy, I'll show you the existing one tomorrow and give you prices.

Thanks

[s class]

The new diff drain plug I picked up from the dealer was pre-coated with loctite.........



Diff back plate after cleaning :