PTU Build Thread

[Ecoboost_xsport]

So, this is my attempt at doing what little we can to improve the PTU with what is currently available. I’d also like to make it a resource for those of you looking for detailed photos of the latest version of our PTUs (which has the cooler). I’ve completely torn down the PTU, and sourced all brand-new seals for it. I will keep the photos at max resolution so apologies for their size, but some may find it helpful.

In this photo, looks like the vehicle is beginning to experience some of those dreaded PTU failure symptoms. Last time I was underneath the truck, I saw quite a bit of oil covering the body of the PTU, and soaking the portion of the exhaust that sits underneath it. It hasn’t failed, in that I don’t have any drive-ability issues yet, but it is coming I’m sure. I will say, that I have NOT been proactive with changing of the fluid. Not because I’m lazy but because I was not aware of the PTU issues until very recently. Call it my ignorance on it, but regardless, I’m glad I caught it when I did. It’s a 2015 with just a hair over 30K miles on it. I don’t drive it much, believe it or not, this is pretty much my dedicated project car.



Anyway, being the consummate prepper that I am, and wanting to keep downtime to a minimum, I went and purchased a brand new one before I am even taking the old one out.

Ford Part Number: DG1Z-7251-F

My punch list for things I want to accomplish with this:

• Change drain plug to bottom of case in order to ensure complete drainage of fluid when performing oil changes.

• Extend hose from vent to top of engine bay to facilitate future oil changes and fills.

• Send all gears and cast components to receive WPC treatment (WPC Treatment).

• Send all gears, cast components, bearings and case to receive cryogenic treatment (Nitrofreeze).

• If possible, research possible higher quality bearings to replace existing ones.

• Apply gold metallic radiant heat reflection material to outside of case.

Now I want to say, I truly believe if you have an older SHO/Flex/XSport that doesn’t have this cooler, you COULD make this version with the cooler work. It would take some effort, but I am certain it could be accomplished. You’d have to buy the hose:

Ford Part Number: BB5Z-8A519-G



Then run your lines through an aftermarket pump and heat exchanger of some sort. It would be a pretty trick setup if done right.

And for those of you wanting to do just that and get REALLY fancy by using the included temperature probe to wire up to the pump or some sort of temp gauge, I think I did some of the legwork for you on giving you some data on the output of that probe and how it correlates to temperature. I figured since I have it off and I have the tools to do this, I’d pass this onto you guys. What I did was use two of my Fluke meters, using one that has temp reading capability with a probe end right next to the actual probe itself, and use the other meter to read the resistance output of the probe at various temperatures. I created those various temps using ice water then boiled water. Dipping the end of the probe into the liquids and taking temp recordings at various intervals. Here is a simple spreadsheet showing the results. This may help those interested in the scaling of this particular temp sending unit:



As I disassembled it, here is what the cooler actually looks like. It isn’t very complex, I wonder if there is any way to improve it:







So, before I started complete disassembly, I ordered a replacement for every single seal, gasket or one-time-use part as I wasn’t sure how much I would destroy trying to take them apart. Below is a list of all the Ford Part Numbers you will need as far as seals or seal kits go:

• 7T4Z-7086-A (Qty: 1)

• 7E5Z-7H469-C (Qty: 2)

• DB5Z-7275-E (Qty: 1)

• GB5Z-7275-A (Qty: 1)

• 7T4Z-7R284-A (Qty: 1)

This does NOT include replacement of the cooler medium. The edges of it are rubber, but it was in good shape and I couldn’t find the part number anyway.

Here’s a bag of all the old seals after being removed. The stuff in this bag will be thrown away, but not until it’s all done, LOL:

 

[Ecoboost_xsport]

When you take it apart, make sure you have some sort of catch for the oil that will come out, as it comes filled from Ford. I have a large oil drip cookie sheet that I was working on. Worked great! BTW, I forgot how much I hate the smell of gear oil…

When you finally get it apart, you will find it somewhat difficult to remove the gears from the side of the case. In order to remove them, you will have to basically destroy the white end seal/plastic cover that is pressed onto the end of one of the gears. Make sure you get a new one, but once you do, don’t be afraid to just break it, it’s hard plastic. Once it is off, the gears will all come out one after the other.





I just used an air impact to remove the nut off the end of the pinion gear. That nut will be replaced and is included in the new parts kits. Be advised, many of the seals will have to be destroyed when removing them.

I decided to remove all the seals as I wasn’t sure if my disassembly would damage them at all and, more importantly, they may not survive the cryo process. So, when I send all the parts to cryo, they will be disassembled bare metal.













As for the bearings. My goal is to try and source some higher quality ones, if they exist. I imagine Ford made some specifications for bearings they needed, then sent out the contract for the lowest bidder to meet those specs. Most of the bearings are Iljin, whom I’ve never heard of, but looks to be a Korean company. I’ve found some in-depth documentation on some of their bearings but so far, nothing about the ones within the PTU specifically. I’m hoping to find some equivalent or better versions via Timkin or Torrington, maybe some SKFs. I removed as many of the bearings as I could:



The only one I cannot remove was the one behind the pinion gear head. It sits in a recessed pocket and no puller can get behind it without destroying the bearing cage. Even though I will begin the process of looking for better grade bearings, I didn’t want to risk destroying this one as it may end up being a unicorn bearing and not easily sourced/replaced.

ASSISTANCE FROM FORUM MEMBERS: If anybody has an old PTU that they replaced laying around and can take it apart and either send me the pinion gear with the bearing on it or feels like removing it (even if it’s destroyed) and tell me what the part number is, I can better research it. For some reason, of all the bearings in this PTU, the parts numbers are not showing on the visible end. I think they are on the backside.



ASSISTANCE FROM FORUM MEMBERS: Although I have some good resources for locating bearings, I am always open to “crowd-sourcing” this task. If any of you guys have a good bearing “guy”, here are some of the bearing numbers:













Anyway, here are all the parts I’ll be sending to WPC:



I spoke with one of their reps regarding having parts with bearings still pressed onto shafts. Their response was, although they recommend removal of all roller/ball bearings, they CAN still apply the WPC treatment, but it is absolutely imperative that a very extensive and thorough cleaning job be accomplished on the bearing prior to installation. They do ultrasonic cleaning, so it should be pretty good, but I also have a high-quality industrial grade parts washer I will put all the parts through as well once they come back.

The cryo treatment will be performed after the WPC treatment and I will include every metal component I can for that one. It will be sent over un-assembled except I will re-press all the bearings back onto their respective location. I use a bearing heater prior to pressing them on (it gets pretty damn hot) and don’t want that to cancel out any gain provided by the cryo treatment in doing so. I will do final assembly and seal installation after it all comes back home. There is no case gasket but looks like they used something similar to Yamabond, which I’ve used successfully to seal Harley Davidson Twin Cam cases. It should work fine in this instance as well. Then fill it with some Amsoil Severe Gear Oil:

 

[Ecoboost_xsport]

And finally, the piece-de-resistance, the reflective material.



My heart tells me this is snake oil, but my brain tells me that the logic behind it is sound. I figured, what the ****, what harm can it do. It really only works to reflect radiant heat, so not sure how effective it is in the real world, especially where I will be putting it. Anyway, just doing every small thing possible to keep this thing cool, which is really the true killer of this thing.

I know it’s been said that regular oil changes can keep this thing alive, but figured I’d try a few additional steps.

So, right now, I’m getting ready to pack the parts up for the WPC treatment. As I proceed with the PTU build, I’ll post updates…

Thanks!

UPDATE 01: Internals back from WPC. Now to press the bearings back on and off to cryo...



UPDATE 02: I know the idea of using a small reservoir was being thrown around and that gave me an idea. I had this thing laying around and it was originally going to be used for my meth tank to be filled remotely. I got it from ProMeth. I've since gone to a different meth tank and never used this but it looks perfect for what will be done:



I am also about to extend that vent hose, but...PLOT TWIST...will NOT be connecting it to the reservoir. I'm just going to extend it up higher, just to be higher, LOL. But what I WILL be doing is....drilling for another hose fitting. After reading about how long it can take to get the fluid down the vent hose. I figured the air is just fighting you, but if there was another line..it would be WAY easier. Not only that, but the hose fitting at the bottom of that reservoir allows for a slightly larger hose to be used. I'm going with 1/2" on it. with a 1/2" hose barb fitting.

This photo shows me mocking up where it will go, but that isn't the actual fitting I will use, the actual one will be smaller and stainless...



See...plenty of room inside the PTU for it:


Anyway, should facilitate fluid changes more easy. I'll update when I get closer.

To Be Continued...

 

[Jbeck]

The cooler....how much clearance do you have on the exterior side opposite the PTU?

Bearing...try looking at Timken LM503349A/ LM503349A-LM....Bore45.99mm, OD 74.98mm, T-Size 18.0mm

 

[Ecoboost_xsport]

The cooler....how much clearance do you have on the exterior side opposite the PTU?

When it comes back from the shop, I'll get under it and measure. It's getting some work done so it's not accessible at the moment.

 

[4sfed]

Great stuff! Good luck with the build!

Question though on the reflect a gold....does it hold excess heat in the object you're trying to protect? I ask because a quick read of the description says it's insulated. Wouldn't that hold the heat already within the ptu, not letting it escape as quickly as it might have normally?

Sent from my Pixel 4 XL using Tapatalk

 

[Jbeck]

When it comes back from the shop, I'll get under it and measure. It's getting some work done so it's not accessible at the moment.

If you have clearance then I might have an idea to make that cooler more efficient. do you have access to a machine shop?

 

[Ecoboost_xsport]

Great stuff! Good luck with the build!

Question though on the reflect a gold....does it hold excess heat in the object you're trying to protect? I ask because a quick read of the description says it's insulated. Wouldn't that hold the heat already within the ptu, not letting it escape as quickly as it might have normally?

Sent from my Pixel 4 XL using Tapatalk

Yes, it insulates, I think the biggest source of heat against the oil inside the PTU however is the catalyst that is very close to it. If anything, I could find some non-insulating reflective material...

 

[Ecoboost_xsport]

If you have clearance then I might have an idea to make that cooler more efficient. do you have access to a machine shop?

Yessir I do have access to a machine shop. I work in one, LOL.

 

[jman1200]

 

[Jbeck]

Yessir I do have access to a machine shop. I work in one, LOL.

Great! well from one machinist to another.. you should understand where Im going on this...IF you have the room, mill you a finned heat-sink to mount on the side of the cooler to draw the excess heat out to ambient airflow to dissipate. You can use a couple nearby bolts to secure it as long as it makes contact with the cooler outside surface, use thermal heat paste to ensure a quick and controlled heat transfer from PTU to the heat sink and it should dramatically reduce the internal temps of the oil....you could go a step farther and drill and tap the exterior cover to include a temp sensor to read PTU temp on dash too...

 

[Ecoboost_xsport]

Great! well from one machinist to another.. you should understand where Im going on this...IF you have the room, mill you a finned heat-sink to mount on the side of the cooler to draw the excess heat out to ambient airflow to dissipate. You can use a couple nearby bolts to secure it as long as it makes contact with the cooler outside surface, use thermal heat paste to ensure a quick and controlled heat transfer from PTU to the heat sink and it should dramatically reduce the internal temps of the oil....you could go a step farther and drill and tap the exterior cover to include a temp sensor to read PTU temp on dash too...

Yeah, I was looking at how much material that cooler body has on it and was entertaining the idea of machining that itself. Not sure its feasible though. Its possible to do your idea as well. As for PTU temp, it's already being monitored via the PCM as it has a temp sending unit. It's one of the gauges I have displayed on my torque app.


Edit: well the body of the cooler is irregular and curved so would be difficult to simply machine a flat surface...BUT...follow me here. It's easy to create a 3D scan of the cooler cover and have one 3D printed to use as a mold for an aftermarket one or use the scan data as data for a CNC machined one that can have cooling fins incorporated...this is something I may actually entertain. Need to find a good CNC shop that can map the existing cover and create a finned one...hmmmm.

 

[Jbeck]

Yeah, I was looking at how much material that cooler body has on it and was entertaining the idea of machining that itself. Not sure its feasible though. Its possible to do your idea as well. As for PTU temp, it's already being monitored via the PCM as it has a temp sending unit. It's one of the gauges I have displayed on my torque app.


Edit: well the body of the cooler is irregular and curved so would be difficult to simply machine a flat surface...BUT...follow me here. It's easy to create a 3D scan of the cooler cover and have one 3D printed to use as a mold for an aftermarket one or use the scan data as data for a CNC machined one that can have cooling find incorporated...this is something I may actually entertain. Need to find a good CNC shop that can map the existing cover and create a finned one...hmmmm.

I think you are onto something there.....I myself would just machine from square or rectangle billet and once all the fins are there and you like it just shape the profiles on a simple band-saw then clean up with a hand-file...it would achieve same result in half the time and no programming

 

[Ecoboost_xsport]

I think you are onto something there.....I myself would just machine from square or rectangle billet and once all the fins are there and you like it just shape the profiles on a simple band-saw then clean up with a hand-file...it would achieve same result in half the time and no programming

Only reason I'm leaning toward the CNC route....its repeatable and could end up being a product offered here and I like the idea of the cover itself integrating fins over having a piece bolted to the cover. It wou6make it that much more efficient. But cost may end up being prohibitive, so yours is an option that is very viable.

 

[Jbeck]

Only reason I'm leaning toward the CNC route....its repeatable and could end up being a product offered here and I like the idea of the cover itself integrating fins over having a piece bolted to the cover. It wou6make it that much more efficient. But cost may end up being prohibitive, so yours is an option that is very viable.

and you are thinking long term and that is good but slow down just a tad and make a prototype to modify and massage however you need to first, then once it is proven you have a working prototype that can be manufactured from there....just my $.02

I agree totally on having a finned cover...that would be the ultimate goal IF it was just as efficient or more as the bolt on type...that can only be determined by monitoring the temps under load as you will already be doing. I think if there is room in there for this type of work to be done and it produces satisfactory results then you are providing a very needed resource to the Gen 4 community and if I can help in any way let me know...I am down

 

[SM105K]

Something to think about. I hope this isn't all in vain brother. PTU's have not exhibited failures because they are physically broken by high HP or TQ. Matt from Gearhead as posted about a billet case, but the internals are more then enough...with proper lubrication.

PTU! Understanding why it fails and ways to prevent failure.

Yes that thing. Here is a very good explanation by a member on here named Mr.HighCaliber.


"PTU's don't fail at least not from a power handling perspective. These only fail from lack of maintenance. Spun bearings and galling of the gears from lack of lubrication.

High Heat dries up the lighter oil molecules in the ****, which causes more heat due to lack of lubrication (thermal runaway) which leads to the remaining gear oil turning to thick black paste which clogs up the vent tube in the ptu which cause pressure buildup in the ptu which forces the remaining, non-congealed fluid out past the shaft seals. Now the only left is a thick paste thats easily flung off of the gears, sticking only to the case. After this chain of events, the bearings run dry and begin to fail, next are the gears. Tolerances widen or things begin to sieze. Bearing and gear noise are usually the first signs of mechanical failure.

But the PTU internals are stout. The weakest part of our powertrain is the RDU Atc coupler. (The electronic coupler in the rear differential). At least in terms of tq capacity and power handling."

 

[6500rpm]

Imho, from what I've seen on failed units they all show excessive heating of the gear oil, or leaking at the seal between the transaxle and PTU. At best, it's only designed to hold 17oz of gear ****, so there's very little fluid for heat dissipation.
Make it easy to change the fluid on a regular basis would be a priority. A second, probably easiest fix that everyone seems to ignore would be ducting to move air across the PTU/converter and get rid of the heat. Unless you're putting massive amounts of torque through the unit, I think bearing/gear failure is just an after effect due to lack of lubrication. I deal with OEM stuff, not modified, and the failures were fairly common a few years ago on bone stock power trains.

 

[Ecoboost_xsport]

Something to think about. I hope this isn't all in vain brother. PTU's have not exhibited failures because they are physically broken by high HP or TQ. Matt from Gearhead as posted about a billet case, but the internals are more then enough...with proper lubrication.

PTU! Understanding why it fails and ways to prevent failure.

Yes that thing. Here is a very good explanation by a member on here named Mr.HighCaliber.


"PTU's don't fail at least not from a power handling perspective. These only fail from lack of maintenance. Spun bearings and galling of the gears from lack of lubrication.

High Heat dries up the lighter oil molecules in the ****, which causes more heat due to lack of lubrication (thermal runaway) which leads to the remaining gear oil turning to thick black paste which clogs up the vent tube in the ptu which cause pressure buildup in the ptu which forces the remaining, non-congealed fluid out past the shaft seals. Now the only left is a thick paste thats easily flung off of the gears, sticking only to the case. After this chain of events, the bearings run dry and begin to fail, next are the gears. Tolerances widen or things begin to sieze. Bearing and gear noise are usually the first signs of mechanical failure.

But the PTU internals are stout. The weakest part of our powertrain is the RDU Atc coupler. (The electronic coupler in the rear differential). At least in terms of tq capacity and power handling."

Imho, from what I've seen on failed units they all show excessive heating of the gear oil, or leaking at the seal between the transaxle and PTU. At best, it's only designed to hold 17oz of gear ****, so there's very little fluid for heat dissipation.
Make it easy to change the fluid on a regular basis would be a priority. A second, probably easiest fix that everyone seems to ignore would be ducting to move air across the PTU/converter and get rid of the heat. Unless you're putting massive amounts of torque through the unit, I think bearing/gear failure is just an after effect due to lack of lubrication. I deal with OEM stuff, not modified, and the failures were fairly common a few years ago on bone stock power trains.

I agree with all of this. Heat is the number one killer here. I would LOVE to find a way to increase the oil capacity, that would help here tremendously. It may very well be all in vain, but since I'm in it and it's opened, why not just make it stronger anyway? If we can keep that thing cooler, I am open to any solution, however minor. The problem with the heat issue is that, once that oil gets past it's designed temps, its never truly the same. Kinda like hard-boiling an egg, once it's boiled, that egg-white will always be white, never going back to its original state, regardless of what temperature it cools back down to. If the temp can be kept to a minimum, it will help to extend the life of it and all the internals. And yes, frequent oil changes are critical. Keep in mind, my vehicle is quite a bit heavier and thus, sees some additional stresses trying to move this thing down the road. I'm looking for every small bit of improvement that aggregates into a better performing piece.

And if it all is for naught, well, then I have some cool internal parts with a fancy cooler cover. It wouldn't be the last part on the vehicle that is ends up being more for "show" and less for "go", LOL. But I also tend to over-engineer things, my brain works that way, so...

As for ducting, I don't know if the SHO has that same "squirrel catcher" that the XSport has that brings cool air to the rear catalyst, but I've already experimented with some cardboard cutout of something that is larger and brings air to more places near the firewall ti include the PTU. Still in design (i.e., cardboard) phase, LOL.

 

[Jbeck]

I agree with all of this. Heat is the number one killer here. I would LOVE to find a way to increase the oil capacity, that would help here tremendously. It may very well be all in vain, but since I'm in it and it's opened, why not just make it stronger anyway? If we can keep that thing cooler, I am open to any solution, however minor. The problem with the heat issue is that, once that oil gets past it's designed temps, its never truly the same. Kinda like hard-boiling an egg, once it's boiled, that egg-white will always be white, never going back to its original state, regardless of what temperature it cools back down to. If the temp can be kept to a minimum, it will help to extend the life of it and all the internals. And yes, frequent oil changes are critical. Keep in mind, my vehicle is quite a bit heavier and thus, sees some additional stresses trying to move this thing down the road. I'm looking for every small bit of improvement that aggregates into a better performing piece.

And if it all is for naught, well, then I have some cool internal parts with a fancy cooler cover. It wouldn't be the last part on the vehicle that is ends up being more for "show" and less for "go", LOL. But I also tend to over-engineer things, my brain works that way, so...

As for ducting, I don't know if the SHO has that same "squirrel catcher" that the XSport has that brings cool air to the rear catalyst, but I've already experimented with some cardboard cutout of something that is larger and brings air to more places near the firewall ti include the PTU. Still in design (i.e., cardboard) phase, LOL.

Electric oil pump and remote reservoir would certainly aid in that solution....Earl's makes a really good electric oil pump.

 

[SM105K]

I agree and there is a correlation between PP and no PP PTU failure rates as well. Cooling is 100% needed and I am glad you went into detail about that.

It is a poor design in fluid capacity for sure, how they are a damn strong little unit when not compromised by heat. We can all agree, the SHO and Xsport should have been rear wheel drive with the ability to transfer power to the front via transfer case.