Teflon tape on differential drain plug

[matthewr87]

So, I've changed the diff fluid every year for the last four years on my 2016 GT350. My experience is that:

There is no drain plug on a GT350 diff - the drain plug hole is where Ford put the outlet line for the diff cooler system. The easiest way to drain the diff is by removing the snap ring on the lower pump line fitting and pulling the lower hose off. Don't bother with taking the fitting out of the diff (the service manual shows this, but It's not necessary).

The fill plug works just fine without any additional treatment. It has no tendency to leak because it's not submerged in oil like a drain plug would be. Take it out, fill the diff, put it back in and tighten it up. Personally, I WOULD NEVER use teflon tape on a steel plug going into aluminum. Teflon lowers the friction and you could crack the expensive and hard to replace housing if you snug it up too much. Besides, there's no benefit.

Thanks for this!

The lower pump line fitting you speak of is the one that comes out of the "drain plug"? Or is it further along the way?

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[JAJ]

Thanks for this!

The lower pump line fitting you speak of is the one that comes out of the "drain plug"? Or is it further along the way?

Yes, it's the one that comes out of the bottom hole that would have a drain plug in it if you didn't have a diff cooler. If you look at the cooler fittings from below, you'll see what looks like a wire snap-ring on it. That's what it actually is. The fittings are a (fairly tight) slip-fit with an o-ring seal . The snap ring keeps them from coming apart when you're driving. To drain the diff, remove the ring and pull the hose fitting directly away from the diff.

 

[matthewr87]

So I managed to come across a video of a guy doing the fluid change as described above. Figured I would link it here for posterity:

 

[Jaymar]

I know I'm a bit late to the party but I'd vote no to teflon tape. Teflon tape is meant to seal a tapered thread fitting and take up the gaps in that thread as well. In this kind of fitting it is the threads that are making the seal. A drain plug seats a taper at the bottom of the plug into a tapered hole and seats with the pressure applied by tightening the threads. Two completely different sealing methods and adding teflon onto a traditional plug type only increases the seat pressure possibly leading to premature failure of the sealing surface. It probably won't be an issue if you don't go gorilla tight on the plug but there are no real advantages gained by using it. The most important thing to do would be to make sure both sealing surfaces are clear of debris that may affect their ability to seal.

Now if you had the diff cooler and there were NPT threads in the fittings that would be where you would need teflon tape.

 

[JAJ]

So I managed to come across a video of a guy doing the fluid change as described above. Figured I would link it here for posterity:

Videos like that are a real problem for GT350 owners. Whoever serviced the diff last didn't do it right, and the guy making the video didn't do it right either.

THE CORRECT FILL LEVEL FOR A GT 350 IS 9 mm BELOW THE FILL PLUG HOLE.

A brilliant video explaining how to do it wrong. Fantastic. What'll they think of next.

 

[Tomster]

It may have been mentioned, but they recommend using a thread sealer on the threads. Probably any sealer would work, but for warranty purposes, I always use what is spelled out in the maintenence procedure.

Keep in mind that there is no pressure on the fluid and it is supposed to be above the fill line. I dont think a sealer is really that important

 

[matthewr87]

Videos like that are a real problem for GT350 owners. Whoever serviced the diff last didn't do it right, and the guy making the video didn't do it right either.

THE CORRECT FILL LEVEL FOR A GT 350 IS 9 mm BELOW THE FILL PLUG HOLE.

A brilliant video explaining how to do it wrong. Fantastic. What'll they think of next.

Yeah I suppose I should have mentioned this bit. I just haven't seen a video before which demonstrates the method of just removing the clip.

 

[matthewr87]

It may have been mentioned, but they recommend using a thread sealer on the threads. Probably any sealer would work, but for warranty purposes, I always use what is spelled out in the maintenence procedure.

Keep in mind that there is no pressure on the fluid and it is supposed to be above the fill line. I dont think a sealer is really that important

Do you now which thread sealer is mentioned in the procedure? I have the PDF for the diff oil change (from what I think is the shop manual) and I didn't see a thread sealer there. Thanks!

 

[Tomster]

Do you now which thread sealer is mentioned in the procedure? I have the PDF for the diff oil change (from what I think is the shop manual) and I didn't see a thread sealer there. Thanks!

I'll find it and post it here when I get home tomorrow

 

[matthewr87]

I'll find it and post it here when I get home tomorrow

Thank you sir!

 

[NoXiDe]

So I managed to come across a video of a guy doing the fluid change as described above. Figured I would link it here for posterity:

That’s AB he’s a great guy. He’s a tech at Ford as well. Just a super cool dude.

 

[JAJ]

That’s AB he’s a great guy. He’s a tech at Ford as well. Just a super cool dude.

Then he should have read the service manual for the GT350 before he made the video.

 

[JAJ]

Do you now which thread sealer is mentioned in the procedure? I have the PDF for the diff oil change (from what I think is the shop manual) and I didn't see a thread sealer there. Thanks!

The 2016 version of the Service Manual I have doesn't indicate a sealer either. Apparently it's not required. Well, maybe you need it if you overfill the diff. But, if you follow the manual for this specific vehicle (and not some random S550 that's not a GT350), it seems that you don't need a sealer.

 

[Tomster]

Thank you sir!

Ford TA-24-B
It is spec'd for the fill plug for the GT350 transmission, but it is not for the differential. Like I said, there is no pressure on the fluid and the fluid is supposed to be filled to 9mm below the fill hole, so I see no reason to need this. If you still want to use a thread sealer on the fill hole plug and wanted to keep it "Ford", TA-24-B is what I would use.

I dont think I use anything on that plug.

 

[vinniechin]

If you use teflon tape, you should use the yellow tape as the white will just likely disintegrate because of the oil. The yellow is for cast iron pipes (et.al.) and caustic substances like oiis/gas.

I have used teflon tape and sealant on my Jeep differentials with no adverse affects.

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