Transmission fluid question for the experts

[Mox4615]

Been putting it off but finally had some time today to do some fluid changes, changed out RDU, PTU and did a drain and fill on the trans.

RDU and PTU were pretty easily done but I had a little bit of a head scratcher when it come to the trans fluid. Granted this is the first time I’ve done this so my first thought was to remove the leveling plug before the drain plug just in case I wasn’t able to get it off after draining initially. So I cracked the leveling plug and went to remove it and fluid shot everywhere. When I finally stopped I opened the drain plug and let the rest out. Got out a little less than 4qrts. I looked at some videos and wasn’t really into having to take about the air box etc so I decided to fill through the fill port. Long story short when I was pumping fluid back in I was only able to get about 3 1/4 qrts back in until it started coming back out. So my question is it looks like they overfilled slightly from the factory? Or am I missing something?

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[Tbone289]

It needs to be running and up to temperature when you check the level so that fluid is being pumped through the system. It's easier to fill from the vent on top.

Remove the vent, fill with the proper amount, replace the vent, drive until up to temperature (180-200 degrees). While running and sitting level, check the fluid level at the levelling hole.

 

[bgn]

@Tbone289 has the correct procedure. These transmissions are not great, so it's important to make sure you use the right fluid, amount, and procedure.

Transmission fluid temp needs to be between 185-200 F. It can be monitored via Forscan.

 

[dalola]

If everything is at proper levels, you should get ~4.5 qts out on a D&R, and, as mentioned, capacity is checked running, and at NOT.

 

[matmondro]

All of the above. Plus, removing the airbox takes less than 5 minutes.

 

[CajunMick]

Please put that dipstick back!

 

[YV1227]

Got a question here, the removing of the airbox does not apply to the 2025 up right?, the breather you guys are talking about is the hook shape plastic hose attached to a screw on to of the transmission right?, I see it every time I open the hood.
What is the capacity according to the manufacturer? was thinking of doing a preventive change at 10K, just fill it at the recommended capacity and forget about it. The RDU, and PTU will do at next change coming up at 5K

 

[FHFR3Maverick]

Don't forget to pull out the vent restricter when doing the refill or it will take forever... ask me how I know!

 

[Tbone289]

Don't forget to pull out the vent restricter when doing the refill or it will take forever... ask me how I know!

Yes, remove the vent tube by the clamp at the base, don't just pull the cap off the vent tube.

 

[topsin34]

Would love to see a video of your efforts. It may help others. Hope all goes well.

 

[dalola]

Got a question here, the removing of the airbox does not apply to the 2025 up right?, the breather you guys are talking about is the hook shape plastic hose attached to a screw on to of the transmission right?, I see it every time I open the hood.
What is the capacity according to the manufacturer? was thinking of doing a preventive change at 10K, just fill it at the recommended capacity and forget about it. The RDU, and PTU will do at next change coming up at 5K

Correct, the '25/26 EB's are packaged completely different. The breather may be different too, on the pre-'25's, it's right on top of the transmission, not a tube, just a rubber vent, and once removed, ATF is refilled here.

If you are doing a D&R, measure how much ATF comes out, and put that much back in, should be right around 4.5 qts. Make sure you use the proper ULV ATF.

 

[Mox4615]

Thanks for the tips guys. I ended up getting close to 5 in there after I had it running and up to temp, starting trickling out around that point. First time doing it so I’ll know what to expect next go round. Just glad I was at least able to get the same amount back in as what come out.

Looked pretty dark and had some sediment in the bottom but glad it’s done. Heard some stories of PTUs being underfilled but looked like mine was pretty close to what I put back in. RDU is super easy on these trucks.

 

[matmondro]

For those asking, this is what the vent looks like, it's location, and the built in restrictor. It would take an eternity to fill without removing the entire tube.

 

[LPAHL]

Has anyone done a 25 transmission yet? I just did my rdu and ptu. Looking down the road. It seems to me it might be more straightforward with the engine bay redesign/refresh. They all share the same 8 speed transmission so it shouldn't be too different should it?

 

[matmondro]

Has anyone done a 25 transmission yet? I just did my rdu and ptu. Looking down the road. It seems to me it might be more straightforward with the engine bay redesign/refresh. They all share the same 8 speed transmission so it shouldn't be too different should it?

I don't own a 2025+ but I can tell just looking at pictures of the engine bay, it will be a whole lot easier. No airbox removal required. The transmission vent is easily visible and reachable, and on the 2025+ models has a metal tube running straight up out of the top of it. It's just in front of the battery, next to the transmission support mount.

The process for changing/filling/leveling the fluid on a 2025+ is exactly the same as previous models.

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