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Discussion Starter #1
OK. I must be a moron. Riddle me this, oh great GM techs:


What's the difference between the GM part no 12378261 synthetic lube @$29.02 / qt from myfriendly local GM stealer and the $8.18 / qt Mobil 1 75-90 synthetic lube at AutoZone? Is there iron-clad proof that if I use the $8 lube I'll void warranty or what? I'm approaching the 5k mile maintenance and would like to get to the bottom of this.


The only things I feel comfortable spending $25 or more / qt are aged in oak barrels for several years.
 

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The differnce is minimal. Well, actually its 17.00 bucks or so. Some like to stick to oem fluids just becuase its oem. lots of people are running the mobil 1 with no problems. I am going to switch over to Schaeffers lube in mine. Just make sure its decent stuff your puttin in.
 

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Discussion Starter #3
Thanks for the info! I greatly appreciate it.
 

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Discussion Starter #4
Changed the rear diff this weekend and it was at least 2" low. Glad I changed it (used the Mobil 1 syn 75-90). The magnet on the drain plug had a decent amount of crap on it. Thanks for the info!
 

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I asked the parts guy at the Chevy dealer how many qts. of the 'grape juice' I needed for a rearend change and he didnt know, so he went out to the service dept. to ask the Techs. how many qts. it takes and he came back splattered in grease with the one bottle he took for example all beat up and greasy. The techs. told him they would answer the question for $85.00. So I left, No Sale.


~SO~ How many quarts. should I buy of the Mobil 1 syn. ?
 

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Since you asked about "Grape Juice", you've got the G80 locker in the back? If so, 4 qts.


Actual capacity according to GM is 3 3/4 qts, but that's to about 1/2 inch below the fill hole. I think most folks are just bringing it up to the hole.
 

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Im pretty sure its the G80, but its a LS not full locker ....


Thanks, I'll just get 4 qts. of the Mobil syn. and see how it goes
 

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Is "grape juice' the oil itself or an additive? I've used the GM posi additive in my car before, is it the same thing?
 

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BERK said:
Is "grape juice' the oil itself or an additive? I've used the GM posi additive in my car before, is it the same thing?
I'ts the oil, not the additive we used to use in limited slips.
 

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Check both the rear and front differential fluds on my new 2004 HD yesterday and found that the rear was 1 1/2 quarts low and the front 3/4 quarts low only had 350 miles on it. I would suggest if you have not checked them to do so.


Good information on this web site thanks for the heads up.


$32.10 for grape juice is crazy. Will be going to mobile one or Amsoil when I drain them at 1000 miles.
 

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NEWS FLASH!!!


GM has a bulletin out stating that the rear end fluid is SUPPOSED to be something like 1" BELOW the drain plug. I asked about mine this week and they produced a TSB stating that it is not supposed to be full to the plug.


Dmaxallitech - you may want to check on this and post the TSB so we don't have everyone overfilling their rear ends.


Stefan


 

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OK, what happens if filled up to the plug ?
 

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Newguy said:
NEWS FLASH!!!


GM has a bulletin out stating that the rear end fluid is SUPPOSED to be something like 1" BELOW the drain plug. I asked about mine this week and they produced a TSB stating that it is not supposed to be full to the plug.


Dmaxallitech - you may want to check on this and post the TSB so we don't have everyone overfilling their rear ends.


Stefan






When I checked mine, I could just barely touch it with my little pinky.


Took it to the stealer and they said they were both at the proper level. I asked are you sure? They said yes they were.


Guess they knew what they were doing.
 

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<H1>Lubricant Level Inspection - Rear Drive Axle 9.5, 10.5 Inch Axle</H1>

  1. <LI ="1">Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
    <LI ="1">Make sure the vehicle is level.
    <LI ="1">Inspect the rear axle for leaks. Repair as necessary.
    <LI ="1">Clean the area around the rear axle fill plug.



    <LI ="1">Remove the rear axle fill plug.
    <LI ="1">Inspect the lubricant level. Specification


    The lubricant level should be between 0-10 mm (0-0.4 in) below the fill plug opening.
    <LI ="1">If the level is low, add lubricant until the level is even with the bottom edge of the fill plug opening. Use the proper fluid. Refer to Fluid and Lubricant Recommendations in Maintenance and Lubrication.



    <H4>Notice</H4>


    Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.



    <LI ="1">Install the rear axle fill plug. Tighten


    Tighten the rear axle fill plug to 33 N·m (24 lb ft).
    <LI ="1">Lower the vehicle. </LI>
Edited by: GMCSID
 

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I dont know if it matters, but I believe our rearends are 11.5
 

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My 2500 hd silverado duramax/allison has not had the differentials-front or rear-touched since i bought the rig new.I wasasleep at the maintenance wheel and just dropping it at the dealer for service.I now want to be a DIY maintenance man.Should i CHANGE the fluids in both of them.Currently have 106000km/64000miles on and am planning a cross country trip to Alaska and back in early May.


NO TOWING or HEAVY WEIGHT


Thanks
 

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I always thought that the fill plug was the level of fill as well.


I always get 'em level fill it till it runs out a little and that's that.


Did something change or is GM looking to do a lot of rear axle warranty work ????????


T
NY
 

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I'll bet the value of my axle that filling it till it drips out the fill plug is just fine.


I think what GM is saying is that its 'ok' to be between 0 (level with hole) and 1/2" below the hole.





Burntb4~ HELL YA change your fluids! Wait till you see what the stuff looks like
 

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Anybody have input on a guy putting synthetic 140 weight gear lube in the rear differential on a vehicle that will be pulling a 10,000 lb trailer 25% of the time.
 

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I posted the following here on the 28th:


My 2500 hd silverado duramax/allison has not had the differentials-front or rear-touched since i bought the rig new.I wasasleep at the maintenance wheel and just dropping it at the dealer for service.I now want to be a DIY maintenance man.Should i CHANGE the fluids in both of them.Currently have 106000km/64000miles on and am planning a cross country trip to Alaska and back in early May.


Yesterday i was browsing again and saw a comment from 2MuchFun that said"


Burntb4~ HELL YA change your fluids! Wait till you see what the stuff looks like
.


WHAT A SHOCK this ROOKIE got today when i followed that advice.The thick BLACK sh*t that ran out-compared to the color that was going back in was SCAREY to say the least.Not only BLACK but an hour later when i was looking at the pan there seemed to be a greyish bubbly film over the top.The rear will be done tomorrow.


You people can't possibly understand how wonderful it feels to a guy like me to get STRAIGHT-HONEST-UNBIASED opinions about stuff like this ,after always depending on the DEALER--but constantly thinking that he is gettin ripped off or there was more that should be done.


On top of that --the job gets done right-and for less bucks.So far i have learned about my tranny and done an atf and filter change.Have followed the pics posted here and did a PROPER 11 zerk lube job.Have changed the oil and filter .Have changed the fuel filter.AnD-have managed to help/offer someone else that was having a wind noise problem.JUST A FANTASTIC SITE with a GREAT BUNCH OF POSTERS!!!


This ole boy REALLY APPRECIATES the ed-ja--MA-kation he is getting here.BLESS YOU ONE AND ALL.
 
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