Final drive drain plugs warn smooth... how to drain fluid?

[Old D5 New Owner]

Hello everyone,

I have a new to me but extremely old 1967 Cat D5, and the final drive oil in in real need of changing. However, when I went to drain the oil today I found out why it hasn't been changed. The drive casing has literally warn down over the years so much that the plug is basically smooth with the case. One side I would say there is 3/16" of the square inset fitting of the drain plug so I may be able to get that one out, but the other side is completely smooth, the entire case has warn down to the level of the bottom of the square fitting in the drain plug such that the plug is basically a smooth circle on the surface of the bottom of the drive case. Anyone know if the oil can substantially be removed via vacuum? Or should I try to weld a nut on the the cap to remove it? I would normally do something like that, but given its an oil filled chamber above the plug, and the fact that I have no idea ho thin it is at this point given the decades of wear, not sure I want to go that route if its possible to remove the oil by suction somehow, and if it is, any recs on an inexpensive pump that would remove old 80w-90 (guy that had it put that in instead of SAE 50, so figure I will stick with that.

Thanks everyone, I know I will have a ton of more questions on this thing. I have the service manual, though it isn't very detailed so leaves a lot to be desired, and this machine is new to me, but I have had an absolute blast using to mow down cedar in the 10 hours I've used it so far on my land in central Texas.

 

[lantraxco]

I'm sure you'll get lots of answers, but me I would throw a drain pan under it and drill the plugs with an angle head drill. Let it drain overnight then drill it out a couple sizes larger and use a big mother spiral easy out to remove the plugs. Skid plate welded under there with an oversize hole to protect the plug might be in order too.

 

[grandpa]

They'll come out, just clean them enought to get your breaker bar in the square hole and unscrew them. They are worn as bad as any I have ever seen.

 

[Junkyard]

There should be a lot of meat left on those plugs. Kinda like an iceberg lol. See if you can get your hands on a couple new ones before you go crazy trying to get those out. Gear oil generally doesn’t vacuum worth a flip in my experience. You could use a pump of some sort to get it out. I used a two chambered waste oil pump when I’d service the D11 but it had a dedicated tube down into the pan.

I betcha an air hammer with a reasonably sharp chisel will turn them if the breaker bar won’t. You wouldn’t need to weld an entire nut. Just a piece of flat bar or something to give you a good surface to smack with a hammer.

 

[Old D5 New Owner]

I'm sure you'll get lots of answers, but me I would throw a drain pan under it and drill the plugs with an angle head drill. Let it drain overnight then drill it out a couple sizes larger and use a big mother spiral easy out to remove the plugs. Skid plate welded under there with an oversize hole to protect the plug might be in order too.

I will try less invasive methods first, but this seems like an excellent fall back in case nothing else works. I think the one with a little meat on it may come out, assuming I can clean up the edges and get it to turn, but the other one seems like a lost cause. I was about to start hammering it with a chisel but was a little gun shy not knowing how much steel I have left there and didn't want to punch a hole in it! Though I guess if it was that thin, the next rock strike would take care of that for me... so maybe ill just go for it. Just didn't want to grenade the thing just after buying it, as once a final goes, the whole thing is scrap metal, so trying to be careful with it.... thanks!

 

[Old D5 New Owner]

They'll come out, just clean them enought to get your breaker bar in the square hole and unscrew them. They are worn as bad as any I have ever seen.

one of them I agree, but I didn't have any space in there to work to clean up the edges to fir the square head in there, nor enough to pound it in, goin to try and dig a hole and park on edge to give me some more room to work tools under there and see where it goes tomorrow. thanks.

 

[Delmer]

Just weld the nut onto them, you're not going to reuse those plugs are you? They'll turn out with a small pliers after they've cooled. They'll most likely be a pipe thread or standard plug thread that's easy enough to find. If you're worried about it exploding, fill the compartment to the top with oil, then leave the filler hole open.

You could try a chisel to clean those holes up if you want, I'd bet it would work, but not worth it to me. Did you use a good pick or tiny chisel to see if they're really worn that shallow, or if the hole is packed full of hard dirt.

Nothing wrong with sucking it out either, but that would just bother me, plus you want a magnet on the plug if at all possible.

 

[Old D5 New Owner]

There should be a lot of meat left on those plugs. Kinda like an iceberg lol. See if you can get your hands on a couple new ones before you go crazy trying to get those out. Gear oil generally doesn’t vacuum worth a flip in my experience. You could use a pump of some sort to get it out. I used a two chambered waste oil pump when I’d service the D11 but it had a dedicated tube down into the pan.

I betcha an air hammer with a reasonably sharp chisel will turn them if the breaker bar won’t. You wouldn’t need to weld an entire nut. Just a piece of flat bar or something to give you a good surface to smack with a hammer.

I hope there is still plenty of meat, just didn't know what the plug looked like originally to gauge how much depth is left, but I agree Im going to try and find new ones, but if it do that I will have an exposed plug at the lowest point of the tractor, which will just be begging to be hit off and cause a much bigger problem with the threads, so going to try and salvage these first, but agree having extras on hand may prove critical, the ill have to sort out some kind of guard as you suggest. thanks.

 

[DB2]

Good advice about getting new plugs first. Before attempting to un turn I would give them a good rap with a large hammer. May want to weld a ring on the bottom of the case to provide some protection for the new plugs. Keep us posted as to what works.

Thanks

 

[Bill Edwards]

I'd like to fit new plugs there, or do a decent job of welding a nut on for future removal.
I'd weld a little something onto the case so the new or repaired plug is protected from wear/rocks.

 

[alrman]

When you fit the new plugs, they will be sitting proud of the housing & will be getting hit by rocks & dirt - which has the ability to loosen the drain plug.
More than once I have crawled under a dozer to find them missing ... (some operators really have no sight or sense of smell)
As mentioned by others , a very good idea to weld some plate, ring or bars around that area to protect the plug.

 

[donkey doctor]

If you can figure out how to suck the oil out without messing with the plugs I'd leave well enough alone. It's not like you're going to change the oil every couple of weeks. Check out the "Suck bucket' back in some old posts it might be just the thing. Maybe someone can find the post on how to make one. I took a quick look but didn't find the original post. It was a pretty simple rig as I recall. Once it oils changed it's good for quite some time I expect and anyway by then you already know how to get the oil out. You know the old saying
"Keep fooling with it till it breaks" I would weld some protection around both of the old plugs tho. D.D.

 

[Delmer]

I present, the Willie59 Suck Bucket,

https://www.heavyequipmentforums.com/threads/the-suck-bucket.20354/page-8#post-735287

 

[Nige]

I'd be interested to hear Willie's comments on how it sucks heavy grade gear oil.

Oh, and BTW to the OP. Gear oil is not recommended in that compartment because it has been known to take out the silicone rubber in the rings of the Duo-Cone seals. Believe it or not but an SAE50 TO-4 oil is in much the same viscosity range as an 80W-90 gear oil despite the apparent number difference because they're measured using two different scales.

 

[Delmer]

the problem with the suck bucket will be limited suction, like 2-3' of water head usually. Coupled with cold oil, a few feet of small diameter tubing, it will be slow.

Get a gallon pickle jar, punch two holes in the lid, stick in your hoses, then stick a piece of metal tube inside the tube to hold the tube tight, attach to a real vacuum pump (or refrigerator compressor, or air compressor intake) and you'll be able to boil water on a warm day.

 

[John C.]

I've taken out a dozen or so of those from D3 to D9G. The were all 1/2" or 3/8" pipe plugs. All the methods mentioned above for removing that one will work. I usually heated the plug with a welding torch tip to red hot, let it cool and used a small cape chisel to work the plug till loose enough to grab with a pair of pliers. The wear on the case was usually caused by the guard that is supposed to be bolted under the final case being worn or gone. I had a 9G one time that the case was worn thin. I pad welded the cases with the oil out and then dropped some hard face on top of that. Use some teflon tape when you install the new plugs. You can get the plugs and the tape at any hardware store.

 

[DB2]

I thought those plugs were much larger with a copper gasket.

 

[Nige]

I thought those plugs were much larger with a copper gasket.

I think that's the newer generation of FD plugs. The older ones were a tapered pipe thread.

 

[DMiller]

Get the old plugs out, I used to weld a Large Nut on them and allow to cool then Ratchet NO IMPACTS to remove them. Get the housing drained get some sch 80 pipe cut offs at least a half inch larger radius and weld around the outside of the circle as a plug protector.

 

[sled dog]

If you can get the holes cleaned up enough to drive a breaker bar in, put a small hydraulic jack against the bar to hold it up in the hole. A few hundred pounds of pressure, not a ton, and turn it out. The jack and pressure will keep it from trying to walk out of the hole. Once it's loose it should turn easy. It's not like its rusted in...