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Check your fluids on new Superduty

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Old May 11, 2026 | 08:42 PM
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Check your fluids on new Superduty

Just took delivery of a '26 F-250 7.3 in Ruby Red. I have seen other posts about confirming fluid levels, especially on differentials on new trucks. I confirmed engine oil level immediately. After a weekend trip for mothers day, finally got a chance to check things this morning, and I'm glad I did. I added an entire quart to the rear diff before any dribbled out the fill hole. Checked the transfer case, and added 1/4 quart to it to get the same result. Do your due diligence , and don't expect the factory/dealer to cover all the bases. Stay safe out there.
 
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Old May 11, 2026 | 11:27 PM
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Is filling to the bottom of the hole what is recommended for Ford axles currently? I ask because I have read that for Dana axles it is 0.24–0.55 in (6–14 mm) below the bottom of the fill hole. This was in Ford workshop documentation.
 
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Old May 12, 2026 | 05:50 AM
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Originally Posted by Stiletto364
Is filling to the bottom of the hole what is recommended for Ford axles currently? I ask because I have read that for Dana axles it is 0.24–0.55 in (6–14 mm) below the bottom of the fill hole. This was in Ford workshop documentation.
I don't believe so, I believe it is a certain distance below the fill hole for everything. What that dimension is varies and I don't know what they are offhand.

Adding fluid til it dribbles back out is no longer proper procedure though, that much I DO know. At least, according to most OEMs' manuals.
 
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Old May 12, 2026 | 06:25 AM
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There's normally a safe zone... usually 1/4" below the hole to completely full and dribbling out, which, while there is no actually measurement given in the 2023 service manual, is exactly what every differential fluid picture in the service manual shows. The AAM on my old Ram was the same.
 
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Old May 12, 2026 | 06:54 AM
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If the OP managed to add an entire quart to the rear diff then it was low.
 
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Old May 12, 2026 | 06:57 PM
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Could not touch any fluid with my pinky . It took an entire squeeze bag quart to bring it to proper level.
 
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Old May 12, 2026 | 06:59 PM
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While we're at it...anybody know the proper ATF level on the ridiculous little plastic dipstick , that's inches away from the hellfire of the catalytic converter ?
 
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Old May 12, 2026 | 07:13 PM
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If you have the 10R100, that's just a cap on the passenger side. The full level is on the driver side at the rear of the trans like a diff. It should dribble out when hot, approx 205 degrees
 
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Old May 12, 2026 | 07:15 PM
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Originally Posted by SMSTX
If you have the 10R100, that's just a cap on the passenger side. The full level is on the driver side at the rear of the trans like a diff. It should dribble out when hot, approx 205 degrees
That's great to know ! Thanks for the info !
 
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Old May 13, 2026 | 05:06 PM
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I was called a dealer hater, told on the forum the dealer knows more than me and as well as the engineers when I pointed this out
I was just trying to save someone from a differential, tcase or engine replacement. ....whatever, Haters going to hate. For anyone to call me out on telling people to check fluids just shows how ignorant they are.
 
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Old May 14, 2026 | 11:15 AM
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I have the 2023-2024 workshop manual. These photos show the Dana M300, but it shows the same procedure for the Dana M275 and M315 axles. For the Ford 11.6 the manual advises the filler hole is mounted too low to add the proper amount of oil so it must be added through the actuator hole for the Electronic Locking Differential.
 
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Old May 14, 2026 | 11:30 AM
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Originally Posted by RadRick


I have the 2023-2024 workshop manual. These photos show the Dana M300, but it shows the same procedure for the Dana M275 and M315 axles. For the Ford 11.6 the manual advises the filler hole is mounted too low to add the proper amount of oil so it must be added through the actuator hole for the Electronic Locking Differential.
My 23 service manual states that this is only for trucks built up to 18 Jan 2023.

Differential Fluid Level Check - Vehicles Built Up To: 18-January-2023
Check
NOTE: The fill hole on the 11.6" is to low for the capacity level needed at this time. To add the correct
amount of differential fluid it is necessary to remove the differential housing cover and drain the fluid. Then
add fluid through the ELD connector adaptor hole.
 
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Old May 14, 2026 | 12:14 PM
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That makes sense kry226, I took delivery of my ordered 2024 in December 2023. I was able to add 4.5 quarts using the filler hole when I changed it.

My transfer case took about 12 ounces to bring it up to the filler hole when \I brought it home, the engine and axles were good.

 

Last edited by RadRick; May 14, 2026 at 12:15 PM. Reason: clarification
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Old May 14, 2026 | 01:23 PM
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Originally Posted by travlnman
Could not touch any fluid with my pinky . It took an entire squeeze bag quart to bring it to proper level.
No wonder why these rear ends are burning up. One would think that Fords quality department would have resolved this issue by now.
 
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Old May 14, 2026 | 01:25 PM
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Originally Posted by RadRick
That makes sense kry226, I took delivery of my ordered 2024 in December 2023. I was able to add 4.5 quarts using the filler hole when I changed it.

My transfer case took about 12 ounces to bring it up to the filler hole when \I brought it home, the engine and axles were good.

This is a big swing and a miss by Fords engineering and quality departments. Cmon Farley this is getting ridiculous.
 
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