Rear Differential Unit (RDU) Fluid Change

[69cuda340s]

Drained and refilled RDU fluid due to the '21s vent tube issue where water dirt can get in. 23k miles. Fluid was not low and not very dirty either. Drain plug had magnet.

Had a hard time getting fill plug out with exhaust pipe in the way. Used 3/8 ratchet with bendable head which was able to reach up in there

Used fluid pump to get gear oil back in. Teflon tape on plugs. Do not over tighten because plug holes are tapered and you could crack housing like I did on my old F150 transfer case.

Other then fill plug remove replace challenges not hard at all. Make sure you turn plugs in with fingers to get started to avoid cross threading.

Eye balled up vent tube in wheel well. Its up there behind felt liner. Mine is straight up early design. Plan to come back and add a loop down to mimic the '22 redesign. Will post up later.

 

[69cuda340s]

Up on lift

 

[Black Horse]

Did 1 quart fill it all the way?

 

[69cuda340s]

Did 1 quart fill it all the way?

Yes it takes a little less then 1 quart.

 

[Fordfan]

Drained and refilled RDU fluid due to the '21s vent tube issue where water dirt can get in. 23k miles. Fluid was not low and not very dirty either. Drain plug had magnet.

Had a hard time getting fill plug out with exhaust pipe in the way. Used 3/8 ratchet with bendable head which was able to reach up in there

Used fluid pump to get gear oil back in. Teflon tape on plugs. Do not over tighten because plug holes are tapered and you could crack housing like I did on my old F150 transfer case.

Other then fill plug remove replace challenges not hard at all. Make sure you turn plugs in with fingers to get started to avoid cross threading.

Eye balled up vent tube in wheel well. Its up there behind felt liner. Mine is straight up early design. Plan to come back and add a loop down to mimic the '22 redesign. Will post up later.

did you add friction modifier as well?..........gotta do this next weekend too

 

[nch5013]

I did mine a few weeks ago after a binding sensation at low turning speed - I worried rear diff. Diff fluid looked great. I went ahead and changed the PTU fluid also - which was murky. The sound/sensation went away when I was done. So I am ASSUMING it was my PTU causing it, but can't be for certain.

Both drain and fill the same way - just different fluid requirements. Both easy - if you do one, I recommend doing both.

 

[69cuda340s]

did you add friction modifier as well?..........gotta do this next weekend too

I bought gear oil with friction modifier already in it

 

[69cuda340s]

Both drain and fill the same way - just different fluid requirements. Both easy - if you do one, I recommend doing both.

I have Badlands with factory towing package and looks like PTU and trans fluid are integrated together share same fluid via lines that connect PTU and trans.

 

[nch5013]

I have Badlands with factory towing package and looks like PTU and trans fluid are integrated together share same fluid via lines that connect PTU and trans.

Interesting. I have a BB and this was not the case. That doesn't seem right, but I'm not looking at your undercarriage... I have the tow as well. I'm sure it's covered somewhere on here. Hell I youtubed mine.

 

[69cuda340s]

Interesting. I have a BB and this was not the case. That doesn't seem right, but I'm not looking at your undercarriage... I have the tow as well. I'm sure it's covered somewhere on here. Hell I youtubed mine.

PTU on Badlands is cooled where as 3 cylinder its not. So they aren't the same.

 

[WildFord]

I dropped the car off for recall service and dealer quoted me $$$ for a 20,000 miles differential oil change. I was thinking maybe I can find another shop to get that done. Not sure if anyone has paid for the RDU fluid change.

so the only challenge is to get the fill plug off? did you have to remove some other parts to access it? all I need is the bendable head ratchet?

you put back in "gear oil"? I did a search on the manual did not find the spec for the required oil.

thank you for all the great info!

 

[69cuda340s]

I dropped the car off for recall service and dealer quoted me $$$ for a 20,000 miles differential oil change. I was thinking maybe I can find another shop to get that done. Not sure if anyone has paid for the RDU fluid change.

so the only challenge is to get the fill plug off? did you have to remove some other parts to access it? all I need is the bendable head ratchet?

you put back in "gear oil"? I did a search on the manual did not find the spec for the required oil.

thank you for all the great info!

To remove the fill plug I used the flexible head ratchet alone and no other parts were removed.

The Ford RDU gear oil part number: XY-75W-QL, Disconnect Rear Drive Unit Fluid, as specified by the official Ford gear oil reference here:

https://www.fcsdchemicalsandlubricants.com/resources/quickreferencecharts

I put Valvoline 75-90 with limited slip additive in mine. That is not the recommended fluid but that is what I put in mine:

 

[mirada]

I dropped the car off for recall service and dealer quoted me $$$ for a 20,000 miles differential oil change. I was thinking maybe I can find another shop to get that done. Not sure if anyone has paid for the RDU fluid change.

so the only challenge is to get the fill plug off? did you have to remove some other parts to access it? all I need is the bendable head ratchet?

you put back in "gear oil"? I did a search on the manual did not find the spec for the required oil.

thank you for all the great info!

 

[mirada]

I didn’t have a ratchet with a bendable head so I undid the muffler at the back ( removed bolts that screwed the hanger brackets into the frame). Was worth the extra 5 minutes to me as I was able to remove with a normal 3/8 ratchet end and screw the plug back in rather easily. Just supported the muffler a bit so that no damage occurred further up. Silver greased the bolts that go back into the frame as a precaution.

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