Whats in your differential?

[Matt400]

Well with all the talk about the rear diffs on the new trucks being low I just had to take a look for myself and guess what- mine was 3 pints low :--) Now I suppose that DC put the fill whole in the wrong location making it now 3 pints over full or the factory machine is short changing the diffs. For now I will run it up to the fill hole.



So whats in your differential?

 

[4xquadrod]

oil level

I believe there was a fairly extensive thread on this once, it was said that the oil level should be about 3/4 of an inch below the filler hole.



It should be in a manual some where. I've heard if you over fill them they can foam up inside?

 

[Matt400]

Re: oil level

Originally posted by 4xquadrod

I believe there was a fairly extensive thread on this once, it was said that the oil level should be about 3/4 of an inch below the filler hole.



It should be in a manual some where. I've heard if you over fill them they can foam up inside?

That is interesting info, I have been searching my DC Shop Manual on that and have not found the fill procedure listed. I did note the capacity of the 2500 rear diff of 4. 75 pints and the 3500 of 7. 65 pints, I found it odd that the 1500 diff is listed as 4. 9 pints.



Am I correct in assuming the 1500 is the 9 ¼ and the 2500 is the 10 ½ and the 3500 is the 11 ½ inch ring gears?

Another interesting bit of info in the DC manual is that the “Trac-Loc” requires limited slip additive where the “Trac-Rite” does not.

The Trac-Loc (limited slip) diff is only listed for the 9 ¼ rear where the Trac-Rite (limited slip) diff is what they have for the 10 ½ and 11 ½ diffs.

I read this as no 2500 or 3500’s with limited slip options don’t need the special additive, just 75W-90 Full Synthetic.

 

[Steve M]

Mine has Valvoline Synthetic up to the fill hole.

 

[Pit Bull]

Guys here are 6 threads that will answer your question on differential fluid and your new type of rearend. Good luck



https://www.turbodieselregister.com...d=389321&sortby=lastpost&sortorder=descending

 

[Matt400]

Originally posted by Pit Bull

Good luck



https://www.turbodieselregister.com...d=389321&sortby=lastpost&sortorder=descending

Good luck is right! That thread is sure confusing. Lets see…we have the owners manual that states ¼” plus or minus ¼” of the fill whole meaning up to the fill whole is full and ¼” below is ok. That info I just read from my owners manual.



Next we have the AAM dealer fax that says ¾” plus or minus ¼” of the fill whole so ½” down is full and 1” down is ok.



Next we have PBeaudoin who spoke to an engineer at American and was told filling to the bottom of the whole is ok, thus confirming the owners manual but contradicting the Fax they sent out the DC Dealers regarding this issue.



Then there is jlevesque who spoke to a DC tech line and was given the same info AAM sent out in their fax.



So from what I gathered from all this mess is nothing except that I will most likely run it at ¼” down where it will satisfy my DC owners manual minimum and still put it at ¼” overfull according to AAM. What the heck!

 

[Matt400]

My personal thought is that AAM goofed on where the fill was located, pretty silly with all this +/- stuff and having to measure down to the oil.

I would rather just change out the cover with a fill that is where it belongs.

If they built one then that would be an admission of guilt so I won't hold my breath.