Rear FX4 Differential Fluid

[MaverickTopGun]

I suspect a simple RTV would suffice here? Or just use a PTFE like Teflon paste? Of course, less is better either way.

I've used RTV & Teflon Tape (not paste) over the years. I didn't know Teflon Paste existed. This does look decent: https://www.napaonline.com/en/p/PTX7651187
Any would work. With a new plug, none needed, although I'd probably still use a small amount.

If smearing something on those threads, got to keep the RTV or paste thread sealer near the outside, first 4 threads only, to keep any bits from floating around inside the clutch packs later.

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[dalola]

Now that we know what we're dealing with, I'll just use a dab of liquid gasket & reuse the plugs. Most folks will probably just screw the plugs back in as-is....and will likely be fine for a couple R&R's.

I'm sure it was cost-down to machine the parts for thread seal vs. a finished seat with a crush washer.

 

[Rivers90]

Does having the Tremor change any of these?

Also if anyone is interested here is the fluid specs and oil change procedure for the PTU. I can post the procedure for the rear diff as well if anyone is interested. Just let me know.

1. Remove the filling ptu plug.

Is the water cooled PTU in the Tremor using the same oil as the air cooled one in the FX4?
And does the dual clutch rear differential in the Tremor use the same oil as the FX4 one?
Are there any other differences between them in the change procedure?

Thank you this post has been very helpful.

 

[Rivers90]

Thanks for sharing! Getting this done ASAP. I'm at just under 12k.

I saw a post where someone used Amsoil 75w-140 for the PTU. Here:

https://www.mavericktruckclub.com/f...-ptu-fluid-service-done-results-photos.19246/

Not too sure about that. Seems like everyone else is saying 75w-85 and using the MC stuff... But damn it's pricey. I'd much rather go Amsoil for that price. They have a 75w-90. Thoughts?

Quick search showed me .5qt for the PTU and 1.4qt for the rear dif?

I think this comes from people with the bronco sport using 75w-140. Not that makes it right for both trucks. Looking at the awd escapes the type of oil may have changed over the years leading to confusion. Ford maybe going to thinner oil to get better MPG.

 

[Rivers90]

Amsoil has a 75w-90 but they add friction modifiers (not sure if that is applicable in this situation or not). The other poster I quoted using 75w-140 doesn't seem to be correct. XY-75W85-QL does specify for limited slip applications you need to add XL-3 (friction modifier). I just can't find any info stating if the PTU or rear dif needs it.

The PTU and rear diff both have clutches with friction plates of some kind so requiring a friction modifier would not be a surprise. But it would be good to find out for sure first.

I am no where near 30k miles but I may change the PTU and rear diff oil early just to do lots of photos and post a how-to. like I did with the engine oil

 

[bgn]

Kind of like what I did with my previous Honda's transmission fluid, I plan to run nothing but the OEM fluids through the PTU and RDU, and also using new caps or whatever they're called instead of RTV. I run my vehicle decently hard and may as well spend a few more bucks. I'll still be saving thousands doing my own maintenance over the life of the vehicle anyway.

 

[Montana]

The PTU and rear diff both have clutches with friction plates of some kind so requiring a friction modifier would not be a surprise. But it would be good to find out for sure first.

I am no where near 30k miles but I may change the PTU and rear diff oil early just to do lots of photos and post a how-to. like I did with the engine oil

No need for a friction modifier in either the PTU or the RDU. Just use the specified MC fluids.

*Edit, for the non tremor models at least. I'd be impressed if it's any different for the Tremor though. Then again... Here we are having torque to yield discussions over drain plug bolts...

 

[bbhaag]

Does having the Tremor change any of these?

Is the water cooled PTU in the Tremor using the same oil as the air cooled one in the FX4?
And does the dual clutch rear differential in the Tremor use the same oil as the FX4 one?
Are there any other differences between them in the change procedure?

Thank you this post has been very helpful.

I only have access to a 22MY service manual so there is no information in it regarding the Tremor package.

As far as the FX4 package is concerned the service manual did not state any differences in oil for it vs non FX4 trim levels. IE 4K tow or just standard AWD with no other options. Again this is for 22MY vehicles.

 

[Montana]

I picked up the drain plug bolts today. There is definitely a pre applied thread locker, but also, they are likely TTY.

Best of both worlds smh.

Looks like I'll be buying extras to have on hand for the 30/60k changes.

 

[Montana]

Did both the PTU and the RDU today. No issues. Pretty straight forward.

Thanks to everyone in this thread for the info!

 

[Rivers90]

Also if anyone is interested here is the fluid specs and oil change procedure for the PTU. I can post the procedure for the rear diff as well if anyone is interested. Just let me know.

1. Remove the filling ptu plug.

It says replace the drain plug gasket. Do we have a part number or link to this gasket?

 

[Montana]

It says replace the drain plug gasket. Do we have a part number or link to this gasket?

It's not necessary. Same as replacing the RDU plugs. The PTU uses a rubber gasket and can be re-used same as an oil pan drain plug that uses them. You just can't over torque it. Mine stopped 1mm beyond the factory markings.

I'll stop by the services window on my way home tomorrow and ask about a part number though. I usually don't re-use rubber gasket drain plugs more than a couple times, maybe 3 or 4 max depending on their quality. And I can't find any info on those plugs at all.

I confirmed today the RDU is not a TTY bolt - they just mention to replace it because they pre-apply a dry thread locker. I tested it after draining and it had plenty of seal left. I went ahead and used the new ones I bought but I won't buy them next time. Totally unnecessary. You can just apply your own thread locker. It looks like they use Loctite 542 or a similar brown sealant for metal pipes. If you are worried about thread locker mixing in, you could just as easily use a thin layer of thread tape. They really don't thread in that far at all to get to torque spec. I think it was only 30 ft/lbs - which is essentially good-n-tight if you don't have a torque wrench. You can feel how tight it is when you are removing them for the first time - not very tight at all.

Also, I accidently bought 2 quarts for the rear dif because my math was wrong. 1.6 pints (what the manual specifies) comes out to just under 1 quart. I read it as 1.6 quarts lol. I even used some to help flush out the older fluid at the bottom with the drain plug off and still had excess when filling.

Anyways... my PTU fluid was pretty gross. The rear dif fluid though - disgusting. Maybe the worst I have ever seen on a new vehicle. Literal thickness gunk built up around the magnet, so I'm going to do it again in another 5k, then every 20-30k. I don't have the luxury of having an open drain pan and I use the same one for everything, but some of that crap even stuck to the outside of the drain pan. I always spray it off with brake clean but that has been by far the worst I have seen. And this is coming from someone who did a gear swap on a Tacoma about 2 years ago. Even at 500 and 1k on the new gears it was not that bad. So I'm not sure wth they are doing but it almost looks like there and excess amount of white lithium used in the assembly process.

 

[Hardening2753]

I'm going to do the initial fluid change at 10k to check the condition. I've been doing a lot of towing. Then at the regular 30k intervals.

I plan on doing the same

 

[Hardening2753]

It's not necessary. Same as replacing the RDU plugs. The PTU uses a rubber gasket and can be re-used same as an oil pan drain plug that uses them. You just can't over torque it. Mine stopped 1mm beyond the factory markings.

I'll stop by the services window on my way home tomorrow and ask about a part number though. I usually don't re-use rubber gasket drain plugs more than a couple times, maybe 3 or 4 max depending on their quality. And I can't find any info on those plugs at all.

I confirmed today the RDU is not a TTY bolt - they just mention to replace it because they pre-apply a dry thread locker. I tested it after draining and it had plenty of seal left. I went ahead and used the new ones I bought but I won't buy them next time. Totally unnecessary. You can just apply your own thread locker. It looks like they use Loctite 542 or a similar brown sealant for metal pipes. If you are worried about thread locker mixing in, you could just as easily use a thin layer of thread tape. They really don't thread in that far at all to get to torque spec. I think it was only 30 ft/lbs - which is essentially good-n-tight if you don't have a torque wrench. You can feel how tight it is when you are removing them for the first time - not very tight at all.

Also, I accidently bought 2 quarts for the rear dif because my math was wrong. 1.6 pints (what the manual specifies) comes out to just under 1 quart. I read it as 1.6 quarts lol. I even used some to help flush out the older fluid at the bottom with the drain plug off and still had excess when filling.

Anyways... my PTU fluid was pretty gross. The rear dif fluid though - disgusting. Maybe the worst I have ever seen on a new vehicle. Literal thickness gunk built up around the magnet, so I'm going to do it again in another 5k, then every 20-30k. I don't have the luxury of having an open drain pan and I use the same one for everything, but some of that crap even stuck to the outside of the drain pan. I always spray it off with brake clean but that has been by far the worst I have seen. And this is coming from someone who did a gear swap on a Tacoma about 2 years ago. Even at 500 and 1k on the new gears it was not that bad. So I'm not sure wth they are doing but it almost looks like there and excess amount of white lithium used in the assembly process.

Did you replace it with motorcraft or go with aftermarket that satisfies OEM needs

 

[Hardening2753]

Yea I'll speak for everyone when I say

Thank you!

Really no reason to not do both at the same time. I had seen people post the how to's on other threads but no pics. This makes it a lot easier.

Also, in case anyone is curious, it's about $100 for the fluids I went through RockAuto. Locally, like everything else, they wanted almost $20 more each. Hell naw. But hey... $100 every couple years or 30k at most - not a bad investment.

It is a shame how expensive OEM brand fluids are

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