Adding a drain plug to your transfer case PTU

eskimo0101

Member
:
2012 Mazda CX-9 Touring AWD
Thanks to member @Avidien we have a thoroughly documented procedure for using a pump to suction out the PTU oil and refill it:
http://www.mazdas247.com/forum/show...-9-transfer-case-gear-oil-(photos)&highlight=
This is a great help but it falls short on a few levels.

1. You're not getting all the fluid out because the suction line can't reach the very bottom. If your fluid has turned to sludge like most have by 20-30k miles you're not getting much fluid out at all.
2. Without a drain plug it's not at all convenient or recommended to try flushing the sludge out using kerosene or some other solvent.
3. Any metal shaving in the PTU will likely remain there.
4. It's a huge PITA dealing with the pump and lines full of horrible smelling gear oil.

Everyone agrees that the ideal solution for our PTU issues would have been if Ford included a drain plug from the factory so fluid changes would be a standard easy to do procedure like pretty much every other vehicle on the road. The users on the Ford Edge forum have taken that theory to heart and come up with a nice DIY for adding the plug yourself. You can find the thread here:
http://www.fordedgeforum.com/topic/10914-ptu-leak-failures

Their user threeputtpar did an amazing job documenting adding the drain plug but instead of requiring everyone here to sign up there to see the pictures I'm going to copy/paste his work here.

Copy/paste of his post below:

Here's the list of tools and parts I needed/used:

3/8"-18 NPT hex head pipe plug from Grainger ($3)
NPT tap and die set with 3/8"-18 from Harbor Freight ($12 with coupon)
5/16" drill bit for pilot hole and 9/16" bit for final hole
Cordless drill
16mm socket with 3" extension and long handle ratchet
8MM hex head bit and 6" extension
Center punch and hammer
New fluid and fluid pump

Here's the start of the pilot hole:
1_pilot_zpsazf63nn6.jpg


And were getting part way into the case:
2_pilot2_zps7bum1cyl.jpg


The pilot hole has broken through:
3_oildraining_zpslcw15psf.jpg


I didn't get any pics of the final hole size drilled or the tapping of it as I was concentrated on not breaking off the tap in the case, so here's the final product:
4_drain_zpszvfbsgbc.jpg



He did add that he recommended using a hammer drill, but I'm not a fan of that suggestion. Hammer drills are for drilling concrete/brick, not metal. Drilling metal you should be using sharp bits, slow speeds and proper drilling oil. The other thing I'll add is to use lots of heavy grease on your tap and clean it often during the tapping process. That will capture the metal shavings so they don't end up in the PTU. When you're done I would suggest dumping some lighter oil, like 5w30 through the PTU to help flush out any shavings that might have found their way inside. I'm going to order the parts for this procedure and do it later this spring.
 
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Great post eskimo, thanks for taking the time for copy and paste for us so we don't need to sign up at the other forum.

This is a "blueprint" for Ford / Mazda recalls, they should be doing this; not us, it would be so easy for them to recall and drill a hole then thread tap and plug it.

I noticed the original poster didn't mention anything about the orange thread rubber sealant or the VC-3 in Avidien's post.
I would think metal on metal with no sealant would leak no ? Also by drilling a hole at the bottom, it now introduces a potential leak path that wasn't there before. Especially in winter, when the coefficient of thermal expansion is different between the plug threads and the case, the oil is bound to leak now that the hole is vertical whereas the fill hole is horizontal on the sidewall and never leaks. I think the correct plug would be a bolt head plug with a hidden rubber O-ring under the bolt head like our engine oil plug like this: http://www.mcmaster.com/#sealing-bolts/=11nydk3 The bolt head will actually prevent driving the plug too deep. The plug he's using is a fill plug set screw type.

I understand his logic, he probably thought for the drain plug , use the same size as the fill plug, BUT there's nothing that says it has to be same. IN FACT, most mfg make it dummy proof and don't make it the same so there's no chance to get them mixed up.

One important thing, original poster didn't mention was when changing oil ALWAYS remove the fill plug first, otherwise, if it gets seized by vacuum when the drain plug is removed first and the case is drained, there's no way to refill the transfer case, and it's up the creek without a paddle.

Again, this is a great post, but it's a balance of pros and cons :

pros: easy oil maintenance, completely remove any sludge/metal particles.
cons: leaking plug, crack case when drilling, seized fill plug, overtightening drain plug...


oh, after thinking some more, one thing I notice is the plug tapered ?? or is the thread tap tapered ??
if not wouldn't the 3/8" NPT plug go right thru the new hole if it's overtightened ? in other words what's stopping the new plug from going all the way into the case ? and what if the new threads gets stripped ? I guess it all depends on how thick the bottom transfer case is right ? if there's not much "meat" there you may only get 3 to 4 threads whereas for the fill hole Ford casted "more metal" around the fill plug exterior to thicken up the material and get more threads.
 
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I would think metal on metal with no sealant would leak no ? Also by drilling a hole at the bottom, it now introduces a potential leak path that wasn't there before. Especially in winter, when the coefficient of thermal expansion is different between the plug threads and the case, the oil is bound to leak now that the hole is vertical whereas the fill hole is horizontal on the sidewall and never leaks. I think the correct plug would be a bolt head plug with a hidden rubber O-ring under the bolt head like our engine oil plug like this: http://www.mcmaster.com/#sealing-bolts/=11nydk3 The bolt head will actually prevent driving the plug too deep. The plug he's using is a fill plug set screw type.

I understand his logic, he probably thought for the drain plug , use the same size as the fill plug, BUT there's nothing that says it has to be same. IN FACT, most mfg make it dummy proof and don't make it the same so there's no chance to get them mixed up.

One important thing, original poster didn't mention was when changing oil ALWAYS remove the fill plug first, otherwise, if it gets seized by vacuum when the drain plug is removed first and the case is drained, there's no way to refill the transfer case, and it's up the creek without a paddle.

Again, this is a great post, but it's a balance of pros and cons :

pros: easy oil maintenance, completely remove any sludge/metal particles.
cons: leaking plug, crack case when drilling, seized fill plug, overtightening drain plug...


oh, after thinking some more, one thing I notice is the plug tapered ?? or is the thread tap tapered ??
if not wouldn't the 3/8" NPT plug go right thru the new hole if it's overtightened ? in other words what's stopping the new plug from going all the way into the case ? and what if the new threads gets stripped ? I guess it all depends on how thick the bottom transfer case is right ? if there's not much "meat" there you may only get 3 to 4 threads whereas for the fill hole Ford casted "more metal" around the fill plug exterior to thicken up the material and get more threads.
NPT stands for National Pipe Thread, it's the standard plumbing pipe fitting thread. plugs are in fact tapered and don't require any sealant.

this is a very sound mod; transmissions and axles used to always have a drain like this, its isn't a problem.
 
NPT stands for National Pipe Thread, it's the standard plumbing pipe fitting thread. plugs are in fact tapered and don't require any sealant.

this is a very sound mod; transmissions and axles used to always have a drain like this, its isn't a problem.


gotcha, thanks for clarifying, I'll have to take it to my local auto shop for this, I trust my guy to do it right, I'd probably mess it up.
 
That's nice! One thing I would change is using a Fumoto drain valve. This way you wouldn't have to worry about threads later on. Definately not knocking the job though.
 
One little disclaimer here though... warranty. My CX9 is a CPO so I'll probably deal with the PITA method of pumping out and refilling until the CPO powertrain warranty is up. If it fails under warranty I could certainly see Mazda claiming it failed because the plug was added.

I would definitely NOT go with a drain valve. First, they're designed for far thinner motor oil not the heavy gear oil. Second, it's an NPT tapered plug that seals because of the taper and the fumoto valve is designed to replace an oil drain plug which seals with a gasket.
 
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Thanks to member @Avidien we have a thoroughly documented procedure for using a pump to suction out the PTU oil and refill it:
http://www.mazdas247.com/forum/show...-9-transfer-case-gear-oil-(photos)&highlight=
This is a great help but it falls short on a few levels.

1. You're not getting all the fluid out because the suction line can't reach the very bottom. If your fluid has turned to sludge like most have by 20-30k miles you're not getting much fluid out at all.
2. Without a drain plug it's not at all convenient or recommended to try flushing the sludge out using kerosene or some other solvent.
3. Any metal shaving in the PTU will likely remain there.
4. It's a huge PITA dealing with the pump and lines full of horrible smelling gear oil.

Everyone agrees that the ideal solution for our PTU issues would have been if Ford included a drain plug from the factory so fluid changes would be a standard easy to do procedure like pretty much every other vehicle on the road. The users on the Ford Edge forum have taken that theory to heart and come up with a nice DIY for adding the plug yourself. You can find the thread here:
http://www.fordedgeforum.com/topic/10914-ptu-leak-failures

Their user threeputtpar did an amazing job documenting adding the drain plug but instead of requiring everyone here to sign up there to see the pictures I'm going to copy/paste his work here.

Copy/paste of his post below:

Here's the list of tools and parts I needed/used:

3/8"-18 NPT hex head pipe plug from Grainger ($3)
NPT tap and die set with 3/8"-18 from Harbor Freight ($12 with coupon)
5/16" drill bit for pilot hole and 9/16" bit for final hole
Cordless drill
16mm socket with 3" extension and long handle ratchet
8MM hex head bit and 6" extension
Center punch and hammer
New fluid and fluid pump

Here's the start of the pilot hole:
1_pilot_zpsazf63nn6.jpg


And were getting part way into the case:
2_pilot2_zps7bum1cyl.jpg


The pilot hole has broken through:
3_oildraining_zpslcw15psf.jpg


I didn't get any pics of the final hole size drilled or the tapping of it as I was concentrated on not breaking off the tap in the case, so here's the final product:
4_drain_zpszvfbsgbc.jpg



He did add that he recommended using a hammer drill, but I'm not a fan of that suggestion. Hammer drills are for drilling concrete/brick, not metal. Drilling metal you should be using sharp bits, slow speeds and proper drilling oil. The other thing I'll add is to use lots of heavy grease on your tap and clean it often during the tapping process. That will capture the metal shavings so they don't end up in the PTU. When you're done I would suggest dumping some lighter oil, like 5w30 through the PTU to help flush out any shavings that might have found their way inside. I'm going to order the parts for this procedure and do it later this spring.

I just did this to my wife's 2011 CX9. It was super easy. Used a cordless drill for the hole. No problems at all, put the hole in exact location as the pics shown here. Glad to have an easier way to drain it TBH.

Edit: BTW the thickness of the metal is pretty substantial here. Mine showed about 3/8" of an inch thick, so plenty thick to hold threads for a plug with no worries of cracking. It was much thicker than I had expected it to be.
 
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Can anyone repost the pics above? Specifically the drill location for the drain plug?
 
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