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OH MAN THANKS for this thread.

Low is an understatement as my front took a full quart of this stuff. The magnet in the fill plug was dry also.

View attachment 917085

Then in the rear I added a little over 1/2 quart of Mobile 1 synthetic limited slip and still could not feel or find the fluid level. Opened up another bottle of the Valvoline in the picture and took another 1/2 bottle of it to get this fluid level.
View attachment 917086

Easy plug to open as it just takes a 3/8ths ratchet. Neither of mine were tight. Of note is my rear plug magnet had some "swarf" stuck on it. With the level so low I found that hard to understand. There is no drain plug on either differential so don't waste your time looking. No sign of leaks. That tells me I just drove and towed 22,000 miles with low differential fluid in my 2019 Cummins 2500.

Another crazy thing is these plugs are in the lower half of the differential. Don't know what they hold but was quite surprised they both took as much as they did. Check yours now and thank the OP for this thread.

View attachment 917087
Just wondering why dslbrnr and you are using 2 different viscosity weights of gear oil.
OH MAN THANKS for this thread.

Low is an understatement as my front took a full quart of this stuff. The magnet in the fill plug was dry also.

View attachment 917085

Then in the rear I added a little over 1/2 quart of Mobile 1 synthetic limited slip and still could not feel or find the fluid level. Opened up another bottle of the Valvoline in the picture and took another 1/2 bottle of it to get this fluid level.
View attachment 917086

Easy plug to open as it just takes a 3/8ths ratchet. Neither of mine were tight. Of note is my rear plug magnet had some "swarf" stuck on it. With the level so low I found that hard to understand. There is no drain plug on either differential so don't waste your time looking. No sign of leaks. That tells me I just drove and towed 22,000 miles with low differential fluid in my 2019 Cummins 2500.

Another crazy thing is these plugs are in the lower half of the differential. Don't know what they hold but was quite surprised they both took as much as they did. Check yours now and thank the OP for this thread.

View attachment 917087
Just noticed you and dslbrnr are using 2 different weights of gear oil, 75-90 and 75-140. Haven't looked up the OEM requirement just wondering
 

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Probably for the same reason I do. The rear diff gets to work hard in my case, but the front one lives a relatively sheltered life.
 

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Stick the tip of your pinky finger in the hole up to the 1st joint then bend it downward, if you just feel the fluid it is about 1" below the hole.
Or mark a zip tie, hold your mark at the bottom of the fill hole. When you see fluid on the bottom of zip tie, all good. (Fill, then check...repeat)
 
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2021 Ram 2500 Big Horn w/6.7 SO & 68RFE, CCSB, Granite Crystal Metallic
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When I read this thread and took my new truck in last week to get inspected, had them check the differentials. Fluid levels were fine thankfully.
 

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2021 Ram 2500 Tradesman Cummins I-6
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YUPPERS! Gotta love the forums.

Brand new 2021 2500 Cummins with 500 miles on it, crawled under for a look see. I could not touch the gear lube, front and back. I had some 80-90w GL5 with the limited slip stuff, about a quart and a half. That got the front and rear diff up to the 1/4 inch below the plug.

I find that very strange to be so low. And how critical is "1/4 in below the plug" anyway?

And I still got gear lube on my face and in my hair.....Nothing smells quite like it.
 

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Discussion Starter · #48 ·
Welcome to the low level club!!
 
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Discussion Starter · #49 ·
I believe anywhere from 1/4” to 1/2” below is what the manual specifies if I remember correctly.
I think most fill until it runs out the hole and never have an issue
 
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I believe anywhere from 1/4” to 1/2” below is what the manual specifies if I remember correctly.
I think most fill until it runs out the hole and never have an issue
Oh I agree completely. Seems kind of fussy.
 

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I fill it to the hole on my AAM diffs. No problems yet. I also have a leaking front seal on my rear 11.5. No drops, only cake, but the fluid is lower but still higher than the line when I get to changing it yearly. So it’s a win.

Also, I heard that the “other” MFG using the same AAM diffs calls for it filled to the hole. I can’t confirm that. But it’s interesting.
 

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Sourdo, you'll get a pass this time, since you're a newbie, but it is not acceptable to use the owners manual as a source for information. Using Google is also not a good way.

What do you think these forums are for?!? Here we can get truth over facts, as it's been said, and lots of opinions to override any facts.
 

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Sourdo, you'll get a pass this time, since you're a newbie, but it is not acceptable to use the owners manual as a source for information. Using Google is also not a good way.

What do you think these forums are for?!? Here we can get truth over facts, as it's been said, and lots of opinions to override any facts.
Did you miss your morning coffee or something? Sit on a stick?

The question was "where is this in the manual?"

And who anointed you the King of this forum anyway? I may be new on this forum, but I am not new to forums, nor diesel powered machines.
 

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Good for you!
 

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I fill it to the hole on my AAM diffs. No problems yet. I also have a leaking front seal on my rear 11.5. No drops, only cake, but the fluid is lower but still higher than the line when I get to changing it yearly. So it’s a win.

Also, I heard that the “other” MFG using the same AAM diffs calls for it filled to the hole. I can’t confirm that. But it’s interesting.
exactly, and what do you suppose will happen a few years from now when the truck gets older and you take it a lube place, they will fill it till it comes out the plug hole. And everything will be fine.
 

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exactly, and what do you suppose will happen a few years from now when the truck gets older and you take it a lube place, they will fill it till it comes out the plug hole. And everything will be fine.
You're assuming that the lube place will remember to A) Put fluid back in, B) Replace the plug.
 

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Take it to a lube place!!! Please!!!

at a point in life when I need quick lube services, I’m not driving a truck that needs it diff fluid changed at anything less than 100k
 

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After a month and 600 miles of easy driving, I decided to check my rear axle today. It had been sitting for 24 hours. The fluid was 1 and 1/4 inches below the bottom of the fill hole. Great job by my dealership. NOT. I am pissed. No wonder I would rather do my maintenance myself.
 
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