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Discussion Starter #1
OK, I'm confused, is it OK to use Mobil1 intead of the grape juice? Does it meet the standards from Eaton for the locker?


And if I use it in the front do I need to also change the breather?


thanks


dan
 

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I put Mobil 1 75W-90 in the front and rear. Yes, it meets specs, (GL-5) and Eric says no problem. In fact, my dealer says that Mobil 1 is a better product. (take that for what's it's worth).


I have a 2004 so my vent is OK from the factory. I think it is white, I believe that the White ones are OK for synth. One of the techs will jump in and correct. Or, you can do a search for front differential vents.


Use any good GL-5 grade synth gear lube and you'll be OK.
 

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I also use Mobil 1 75w 90 syn. Just put my mag hytec on yesterday and hardly any metal fillings in the diff. Good way to go but kind of expensive.
 

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Just changed mine out last night. My truck was built 02/03 and it had the white vent in it, so I don't have to change it. Also, make sure you have a funnel with a long tube on it for adding the fluid back in, it will make it much easier. I also used Mobil 1 75w-90 syn. in both.
 

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I bought this little honey at Autozone for $4.50. It has a slide valve, 12" clear tube and a cap on the end. You simply screw it on the bottle, raise it above the rear and slide the valve to open. I punch a hole in the bottom of the bottle after it starts to flow. You can change bottles without removing the hose. I work over my oil catch pan. The empties go in it also. This job can be done without spilling a drop if you are
carefully. Later! Frank
 

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Dittos Frank! I use the same tool and punch a hole in the bottom of the Mobil-1 bottle. Works Great..
 

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I just changed to Amsoil Synthetic gear lube in the front and rear diffs on my truck. 80W-90 in the front and 75W-90 in the rear. The Mobil 1 75W-90 will work just fine in both the front and the rear though. Had to add the white vent cap to the front of my 01' though. Synthetic is the way to go....
 

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Mobil 1 meets all the specs for the front and rear differentials.

If you have the white breather cap on the front differential then you're already synthetic "compatible".
 

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Mobil-1 meets the specs for the front differential - it does not meet the specs for the rear differential (someone here actually called mobil to confirm this).


I had the rear differential fluid replaced after break-in (thanks patrick!). Patrick put in the oem "grape juice"; I, like others here, used the gm stuff to avoid any potential warranty problems.


- jeff
 

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Discussion Starter #10
WHAT!!!! I changed over to Mobil1 on Tuesday night! I thought I got lucky when I saw the front Had the white breather but, Mobil1 is no good for the back!?!!?


My frustration and confusion exists on many levels!!! I though if it met GL-5 standards it was ok? is it not???
 

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Not to worry... Mobil-1 is GL-5 rated and works fine in the rear. I have 15kmiles on M-1 in my rear diff. I believe Jeff's point is that no one has found an aftermarket lube that "explicitly" meets the GM spec. Therefore the conservative position is to use the GM grape juice. However there is a post by TXDoc that quotes an email from Eaton (the manufacturer of the rear diff) stating that a GL-5 rated synthetic (75w-90 or 75w-140) lube is what's required.


See the post by TXDoc in the following topic:


http://dieselplace.com/forum/forum_posts.asp?TID=2643&KW=txdoc+rear+diff


Edited by: jbplock
 

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Discussion Starter #12
Whew! I though I was going to have to explain to my stealer why my rear diff went out at 11,000.... thanks to everyone who posted with info.



dan
 

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Mobil 1 is fine for both diffs. Not to worry...
 
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