Changed fluid in rear diff today. I thought all 05´ and up had AAM 11.5 rear axle. Mine only took 3.5 qts of fluid to get it to the fill line on diff cover. In the book it says AAM 10.5 fluid level should be 3/4in below fill hole and 1/4in below on the 11.5. The mark on my cover is 3/4in below the fill hole. Thought most people were saying they put 4 - 4.5 qts in their rear diff. Axle tube OD appears to be 3.75in. So did i somehow get a AAM 10.5 or maybe the wrong cover from a 10.5??

 

I think the 11.5 eventually ended up also being 3/4" below the fill hole, or at least that was what a memo my dealer showed me indicated...

 

Would 3in lift in front change angle of rear diff so that less fluid reads higher on the rear cover? Could that be why it only took 3.5 qts to fill to line on cover? Wondering if i should fill up to bottom of fill hole to compensate.Heard that these AAM are pretty sensative to overfilling though, and underfilling for that matter...

Anyone else with lift up front have any thoughts?

 

I would not guess. I would suggest you try to find a perfectly level place to park and then remeasure the fluid level.

My driveway is inclined and the street in front of my house is curved across it's width. So I used the flat warehouse floor at work (checked with a beam level) to park on and check and fill all my fluids to correct levels. I then went home and marked and chocked a point in my driveway and rechecked all the levels and marked those points so I can check my fluids at home. I painted a place on the driveway to place the chock so I always park in the same place when checking.

 

What does the spec sheet in your glovebox say about the axle in your truck?

 

How did you drain out the old fluid? Did you suck it out of take off the diff cover and completely drain it? And I don't think the bolt holes from the 10.5 match the 11.5..

 

Exactly. The sticker in the glovebox will tell you. I think after '03, all the 2500 Diesels have the 11.5.

 

Will check glovebox sticker when i get home. Bolt pattern and shape of my diff cover matches pictures of aftermarket ones for the 11.5, so i wonder if there were different covers from the factory for the 11.5 with different fill hole/ fluid level marks.

Now I'm more concerned about the amount of fluid in the diff. On level ground, wouldn't a 3in lift up front be like parking on a slope with front 3in higher? Therefore giving an artificially high reading on diff cover fill line, with less volume of fluid actually in the diff??? Think I'm going to jack rear axle up 3in to return it to factory geometry and check the fluid level then.

 

I think your sweating it too much. I am positive you have an 11.5, and most put in just under 4 quarts. I put right about 4 quarts, but I didn't realize I was parked nose down. It the lift has put your rear at an angle, that will cause your issue.

 

I ignore what the manual said and just fill up to the hole.

MikeyB

 

X2........

 

Does anyone else have an 11.5 with the fill mark on the cover 3/4in below the fill hole? I just wonder with that mark if my fill hole is higher than those with the fill mark 1/4in below the hole. Think i'm going to split the difference between the fill mark and hole and get on with it!

 

Not all the covers have the line

Bob

 

My 03 didn't have the mark, but my dealer called and told me they got a notice saying not to fill the rear end more than 3/4 below the fill plug or it will blow seals.

My 06 does have the mark stamped on the rear axle.

I lost track of how much it took to fill the rear end, but I ended up with more gear oil left over than I should have (for changing both axles), so I don't think they take as much as the volumes listed in the book.

Lastly, considering the wheelbase of the truck I don't think a 3" lift in the front wouldn't change the angle of the rear differential enough to make any meaningful difference.

If it has the fill line, and you've filled it to that line, I wouldn't worry about it. An appropriate size allen wrench makes a good dipstick to measure how much below the bottom of the fill hole the oil level is.

 

...x3
I think you worry too much...