RDU oil leak...

[ppagan2012]

After only five months of replacing the RDU, this happens. A loose axle and oil leak..

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[paneubert]

Is that a crack around the plug in the first photo?

 

[ppagan2012]

Is that a crack around the plug in the first photo?

I honestly hadn't seen that part. I'll take a look at it tomorrow. Thanks for the observation.

 

[Tbone289]

Yeah, the possibility of that being a crack is concerning. It looks like the leak is definitely from the CV axle seal, however.

 

[A.Bursell]

Is that a crack around the plug in the first photo?

At first I thought it was just a casting line, but when I clicked and enlarged the photo it does have the appearance of a crack. Still hard to tell from the photo. But I also noticed it looks like the fill plug there is not threaded in very far and appears to have teflon tape coming off of it. Teflon tape is not called for there, and it if were to have been cross threaded or maybe even had too much of that tape put on, and someone just rammed it home -- I could see it causing a crack.

The drain plug looks the same way. I'd have to look at mine again, but I feel certain it goes in further -- or again it has a bunch of teflon tape on it keeping it from being installed correctly.

Investigate for sure. Possibly shoddy workmanship.

 

[Vmontello]

Is that a crack around the plug in the first photo?

Also if you look at that crack, the smaller part of the crack seems to have little bubbles in it, kind of like there was a small weld made there to fix it. Does anyone else see that? Or am I tripping?

 

[ppagan2012]

I just cleaned the area and everything seems to be fine. But it is very strange that the axle came off. I already have an appointment at the dealer next Monday for service.

 

[Toddman45]

It's not Teflon tape. That's thread sealant, mostly found on OEM plugs of this type for rearends, ptu, and transmission drain and fill plugs.

 

[Carlitos_92]

Yep, thread sealer. Some of the drain/fill plugs have it from the factory. It seems to usually be plugs without flanges for o-rings or gaskets.

I just did my PTU last weekend but ran out of time before I could get to the RDU, so I don't currently have any photos - but things look off with both those plugs. Here is a great write-up with links to YT videos and elsewhere where you may get some comparisons:

https://www.mavericktruckclub.com/f...-transfer-unit-rdu-rear-drive-unit-oil.44242/

 

[CajunMick]

One thing about those pipe plugs, they normally NPT, tapered pipe threads. And as such the taper is to be considered when tightening them up. Known to crack bosses where the female opening is, when tightening them up too tight.

Also the thread pitch or peak is squared off. So when mated up together, there is a groove which allows a gap, and fluid to weep thru. So that’s why NPT type threads need a sealant or tape to fill the gap, to contain that seepage.

there is a thread class called NPTF, where the thread pitch, end is pointy, and when mated to like kind female, designed to crush at their ends meet, leaving no gap, forming an effective seal. This is typically used in hydraulic circuits. A NPTF can never be mated to NPT types. one will find the number of turns is but couple threads, if at all. Also the male NPTF fitting is usually manufactured of soft material, like aluminum so the mating male n female threads do crush. These type fittings are used just once, then thrown away.

Also, regarding thread sealants, need to read fine prints on their use. Fluid compatibility issue might compromise the effective sealing of the sealant.

Years ago, there was a sealant called John Crane, in paste form. Best stuff ever used in NPT.

 

[Carlitos_92]

Also, regarding thread sealants, need to read fine prints on their use. Fluid compatibility issue might compromise the effective sealing of the sealant.

Years ago, there was a sealant called John Crane, in paste form. Best stuff ever used in NPT.

Permatex 59214 is a good one. Goes to 500F and is hydrocarbon-resistant.

 

[A.Bursell]

It's not Teflon tape. That's thread sealant, mostly found on OEM plugs of this type for rearends, ptu, and transmission drain and fill plugs.

Yep, thread sealer. Some of the drain/fill plugs have it from the factory. It seems to usually be plugs without flanges for o-rings or gaskets.

The plugs come with sealant on them from Ford and the service manual calls for replacing the drain plug every time. I've done mine on this truck (and plenty of other similar) and it doesn't have the "peeling off" look that the OP's does, it looks like teflon tape added to me. I could be wrong but that's why I say that. Nothing should be added, it's not needed.

 

[Carlitos_92]

The plugs come with sealant on them from Ford and the service manual calls for replacing the drain plug every time. I've done mine on this truck (and plenty of other similar) and it doesn't have the "peeling off" look that the OP's does, it looks like teflon tape added to me. I could be wrong but that's why I say that. Nothing should be added, it's not needed.

I guess we aren't looking at the same image. In OP's second set it is clearly a granular paste to my eye.

Anyway, "nothing should be added" to replacement plugs precisely because the OEM plugs come with that sealant already applied. But I'm not replacing drain plugs on Ford's schedule. Hence, I clean the old plugs, apply more sealant, and call it done.

What they did to the plugs on OP's replacement RDU is anyone's guess.

 

[A.Bursell]

I guess we aren't looking at the same image. In OP's second set it is clearly a granular paste to my eye.

First image posted. 6:00-9:00 on the fill plug.

 

[Carlitos_92]

First image posted. 6:00-9:00 on the fill plug.

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