This is an old topic but I just saw a TSB on Geno's site that got me wondering what to do. The TSB is dated May 11, 2004 and the build date of my truck is May 2004. The TSB says the 11.5 rear diff as well as the 9.25 front diff should both be filled up to the fill hole with oil! My rear diff cover has a fill line on it that is about an inch below the hole. Do I now fill it up to the hole? I would think so if this is a new TSB! Also they say the rear should have 75W-140 synthetic oil and the front diff should have 75W-90 non-synthetic oil! What's up with this?
I was going to change my oil this weekend but now don't know what I should buy.

 

I would be interested in seeing the TSB. I changed mine awhile back and put the 75/140 Lube in both my diff's and fill them to the fill hole. I have run them like this for about 15k and have not had any issues. I check them everytime I do an oil change and the fluid looks good.

 

I will try to post the link to the TSB:
http://dodgeram.info/tsb/2004/03-001-04A.htm

 

Thanks for the link. I see they still say +/- 1/4 inch from fill hole. I do not think 1/4 will make a difference in the way the diff's perform. I would rather have a little more lube in them than a little less. I do like the fact that the now recommend the 75/140 lube.

 

just a note in case you did not see it... you need to read the fine print on the TSB... states NOT all drain holes are located correctly...

you need to MEASURE the distance/etc.... do just fill to 1/4 in. to hole... that may not be right!!!

 

That TSB just makes it clear as mud. Do I fill the rear end to the line which is ~3/4" below the hole or 1/4" +/- 1/4 below the hole? Do I use 75W-90 (which is what I used) or change to 75W-140? Why can't they get something as simple as this straight?

 

My feelings exactly.....and I just installed Valvoline SynPower GL5 75W90 in the fronts & rears at 19K miles till it ran out the fill holes a week or two ago.....**** on it; if they deny warranty claims based on their info in the owner's manual, I'll ask..."where's my written notification AAM changed their minds ?"

Greg

 

Here's the skinny from AAM...

Thank you for contacting AAM. We hope the following answers your questions.

10.5" Axle lube fill is 2.5+/- 0.2 litres
11.5" Axle lube fill is 3.62 +/- 0.2 litres

Newer AAM axles have a fill level mark on the coverpan. Neither volumetric levels come up to the bottom of the fill hole. Overfilling will probably reduce your axle efficiency (fuel economy), but should not damage the system.

Best Regards,
AmerIcan Axle & Manufacturing

 

Funny that a company that calls itself "American Axle & Mfg." that I presume is located in America, would reply to an email from an American with fill volumes described in litres.

 

So I have to measure out 3.62 liters? Ridiculous! What ever happened to filling to the hole? I guess they couldn't figure out where to drill the hole. And what lube do they recommend?

 

filling to the hole will make em LEAK!

 

I just changed my oil this morning and I measured out exactly 122 oz just like it says in the TSB. The level came out to EXACTLY at the bottom of the fill hole! This is about 1" higher than the "fill line" on my cover! The other thing that surprised me was the price of the 75W-140 synthetic. It is twice the price of the same brand 75W-90 synthetic. I paid $15/qt at Checker for 75w-140 Mobile 1 vs $7/qt for 75W-90 I checked other stores and found the same thing. Is the 75W-140 twice as good?
It seems there is lots of confusion at DC

 

Since winter is here I just changed out to 75W-90 synthetic front and rear and will go to the 140 for the summer.

 

I beg to differ, I have just under 50K miles and have changed both fron and rear differentials three times now. Every time I have filled to the bottom of the drain hole and I have NEVER had a leak. No evidence of leaks at the end of the axles either.

 

The problem is not the leaking, but "aeriation".. The "foaming" may cause damage since the gears are getting foam and not lubrication...