Hello & Merry Christmas to all that celebrate.
I am in need of some confirmation info. of what I think I know is correct.
I am going to do an oil change in the dif. Personally I don't buy into the lifetime ( never change it) line that Ford is selling. So in looking at the dif. I see a tag with 3.55 so that's settled. I also count the bolts on the cover, there are 10.
In looking at the sticker on drivers door jamb I see axel code of C9. Google search says Ford 10.25 Limited Slip 3.55 ( more confirmation of what I suspect).
Now a little confusion. I had called a dealer some time back with my V.I.N. #. I wrote notes of what I was told...(That it was a DANA 60 with 9.75 ring gear). Now obviously that didn't match the Google info. on a C9 code saying it's a 10.25 ring gear.
Now the only reason this presents as a problem is that in the Owners Guide there are different spec. Oils for Dana 9.75 & the other Dana is listed as 10.5 inch vs. Google search C9 code showing as 10.25?
P.S. The owners guide says the 9.75 (M60-IU) = Hypoid Gear Oil SAE 90.
The Dana 10.5 (M70- 2U) & (M70-1HD) & (Dana135 E-550 only) = Motorcraft 8W-90 Premium REAR axel Lubrcant.
So the question is....What the he'll have I got?
Dana 9.75, 10.25 or 10.5. ?
Do I believe Google's search of C9 saying it's10.25?
I'm questioning this small detail because as can be seen the different (size ring gears) call for different oils.
Not to mention the question of 4 or 8 oz. Of Friction Modifer.
Dana axles seem to call for 8 oz. Of FM meeting Ford specification. EST-M2C118-A.
Though in further study the "Visteon Tracton Lok" seems to require the very same (EST-M2C118-A) but only 4 oz. Of the product. It also referred to it as "XL-3" or equivalent.
I prefer to find & refill with the HYPOID GEAR OIL SAE 90 (if I have properly identified my axel) as I read some stuff about the heavier 75-145 that many seem to be suggesting as an alternative either because Ford has issued a " Revision memo" or maybe that's the most commonly available easy off the shelf to get stuff. I don't know who to trust anymore. Certainly am not going to do something just because Advance or Autozone... Computer says so and the counter person just mimics what he reads on the machine!
ADVICE?SUGGESTIONS? ANSWERS?... THANK YOU FOR ALL RESPONSE'S. DDT

 

The Sterling 10.25" has 12 cover bolts, so your counting 10 says that's not what you have.

You don't say what vehicle you have, but I know that Dana 60 was used in a lot of E-series vans and it has 10 cover bolts, so that would be my first guess. But the Dana 70 also has 10 bolts, so that can't be ruled out just by that.

Dana axles have the model number cast in, so crawl underneath and look around. There will probably be a big "60" or "70" on it somewhere,likely on the front of the casting, to one side or the other of the pinion.

As to what lube to use, I probably can't help you there.

 

Yeah...it's a 2003 e-350 with the 7.3.
I just got out from under it After a little degreasing. I see Dana on the COVER PLATE. But on a plate between 2 bolts I see the 3.55.
Some other numbers cast into the pumpkin are...
47510
3035
There was one other I could not read but it was not 60 or 70.
I'm not sure I even get what is more important to know? Dana 60 , 70 ,80 or what size the ring gear is?
The 60-70-80 all seems to have to do with identifying the cover.?
As I have written about in my OP, The owners manual seems to be more about identifying the ring gear size. That's where they specify for using different types & weights of fluid.???? DDT

 

When in doubt get the higher viscosity oil, I put 85w140 in all of my axles, and if you have the limited slip most gear oils already have the additive in them.

 

 

I don't think there are really any differences in ring gear size with a particular Dana axle. So I think all 60s will have the 9.75" ring gear while all Dana 70s will have a 10.5" ring gear.

And the "60" or "70" cast into the housing isn't subtle! I think the characters are about 2" tall. And they stand proud on the casting, rather than being stamped in.

 

Don't cheap out on the lube. I did this several years ago with an 8.8 and it came back to haunt me when the cheap oil degraded. Had to rebuild the whole ****. This time I used Lucas gear oil, which has friction modifier in it. If you don't have traction loc, it won't affect it.

 

You have a Dana axle, E series didn't use sterling axles.

 

Are you sure it was the gear oil and not another issue that caused this? All I ever use is the cheap stuff and I have never had a problem, all oils and most other automotive fluids have to meet manufacturers specs before they can even be sold to the public.

 

C9 is a 3.55-1 Dana rear axle with Limited Slip.

 

Positive. It was black and clumpy after a year's time. And it's not driven that much.

 

It should have 3L55 on the tag then.

 

Based on information here, From other internet investigations, Calls to Ford dealers. and talking to a couple transmission shops that seemed to also have knowledge of REAR ends.
I will NOT know for sure what size ring gear I have until I pull the cover off and measure it.
My biggest conflict is between believing the actual door jamb " axel code" which I have mentioned is C9. Every internet page says C9 axel code is a 10.5" gear. The "DEALER" who used my V.I.N. # to look up This vehicles " HV BOM" ( that's History Vehicle, Bill Of Materials) For those that might be interested, Says that the info tells him it's a 9.75" ring gear.
Oh, One of the other people I reached out to was a "differential parts expert". He ASSURED me it was a DANA 10.5" gear.
So it leaves you wondering what it's going to be and who is going to be correct.
I think it's the Owners Manual that has made this whole thing so confusing. With all there different fluids for different size & type gears/ differentials.
With the NEW FORD " REVISIONS" It seems like they ALL spec. out for the 70W-145 synthetics oil.
Adding Friction Modifier seems to be up to the individual or what you read on these & other forums. Most seem to say they didn't need to add any because all the new synthetics already have it in the oil. BUT, some report in certain vehicles they still had to add extra because they were chattering. Toyota Tundra comes to mind as one that said he needed it.
That said, they also say you really can't add "too much". Of course that means 4 to 8 oz. FM Plus your required pints of oil. Of course 4 bottles of FM would be to much! Just wrote that before someone else chimed in on that subject. As if anyone is likely to try to fill 1\2 their diff. with FM.
So I opted for the Mobil 1 75W- 90 vs. The " Ford revision" of 75w- 145.
Now I suppose someone is going to tell me how that weight is going to ruin my differential!
After all, this is the internet.
I have to imagine anything (synthetic) will be better than the likely dino oil that was factory filled " for life".
So there's the story for anyone interested or that would Like to add more info or comment on anything I have wrote here. Maybe there is more to be learned if this thread continues?
Maybe not. Thanks for those that have tried to help out in my drama. Lol. DDT

 

Just my 2 cents on synthetic gear oil: I bought a new 06 Mustang GT in 2006, it was filled with synthetic gear oil from Ford, had Trac-loc unit in it. Damn thing was noisy with the synthetic lube. The sqeakin from the clutches slipping everytime you went around a corner. If I recall I had to add an extra bottle of modifier to quieten it down. I used Lucas gear oil in my 96 Van's 8.8, with nary a sound from the clutches.

 

The ONLY reason Ford specs low viscosity synthetic lubes now is because these thinner fluids deliver better fuel economy. They do deliver in this regard but can also result in more noise.. something I have seen first hand.
Ford has always spec'd friction modifier for the Trak-lok diff, and the way you know if you need some is if the diff chatters or is otherwise un-smooth around corners. A small quantity of the modifier added to the diff makes the oil more slippery which means smoother operation but also means your LS diff doesn't work as well as it could, it's your call what tradeoff you want to make. Open diffs don't require FM at all.
I'm pretty sure your van will have a D60 full float axle with a 9.75 ring gear, I believe the D70 was more for the higher payload cab and chassis versions used to build buses and campers.