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.

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.

Thanks for the info! I greatly appreciate it.

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!

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. ?

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.

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 http://www.dieselplace.com/forum/smileys/Big Smile.gif

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?

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.

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.

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


http://www.dieselplace.com/forum/smileys/Embarrased.gif

OK, what happens if filled up to the plug ?http://www.dieselplace.com/forum/smileys/Geek.gif

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


http://www.dieselplace.com/forum/smileys/Embarrased.gif








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.

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

<LI ="1">Raise the vehicle. Refer to Lifting and Jacking the Vehicle (http://service.gm.com/servlets/CellHandler?CellId=47852&amp;RefDoc=860219&amp;evc=sm) 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.
http://service.gm.com/engif/000/000/607/607207.gif
http://service.gm.com/tif.gif (http://service.gm.com/servlets/RetrieveTif?pic=607207)

<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 (http://service.gm.com/servlets/CellHandler?CellId=53256&amp;RefDoc=860219&amp;evc=sm) 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

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

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

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 ????????


Thttp://www.dieselplace.com/forum/smileys/Confused.gifNY

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 http://www.dieselplace.com/forum/smileys/Dead.gif

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.

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 http://dieselplace.com/forum/smileys/Dead.gif.


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.http://www.dieselplace.com/forum/smileys/Hug.gif

Well said! I feel the same way 100%; I've learned some priceless info. and tips here http://www.dieselplace.com/forum/smileys/Clap.gif


Heck, if the dealer didnt treat me -and their own people- so badly, and try to rip me off, I would have let them make a few hundies off me, now Im glad Im doing it all myself thanks to this place :)

The reason for the difference in fill level in relationship to fill hole is due to allow for the expansion of the HOT fluid.

If GM is underfilling, its proabably because they don't want much hydraulic pressure on the pinion seal which leaks just after warranty! http://www.dieselplace.com/forum/smileys/Disapprove.gif Less oil in there, the lower the level at the pinion seal!?


As for fluid, its a bunch of gears, just like they've been for almost 100 years. The Eaton Locker is NOT the same as the limited slip rear of the C/K trucks which required a special anti slip additive. Normal synthetic 75-90 should do just fine.

Why does the GM grapejuice cost so much in the states? I bought mine at the dealer recently and paid $12.06CDN/946ml (1 US Quart). That's approx $9.25US/quart. It's GM part number 12378261. I've seen posts here where dealers are charging up to $29.00 U.S/ quart. Are you guys using liquid gold or gear lube?http://www.dieselplace.com/forum/smileys/Confused.gif I agree that's a ridiculous price to pay for it.


BTW I'm not a GM employee or relative so there is no special discounts that I'm aware of.
Edited by: TC Dmax

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.&lt;!-- Signature --&gt;

I put RedLine in over 50,000 miles ago. Just changed rear covers yesterday and it was as consistant as the day i put it in.... abiet darker and had shiny swirls of metal wear.. I think that's always going to be there.

Getting ready to do the rear diff.today.I just want to verify that i have completed the front diff.PROPERLY.I drained the "MOLASSES" out and left the plug out while SQUIRTING about half a qt of clean fluid in with the hope of flushing out ALL THE CRAP.Black crud kept coming and then it turned to the clean.Cleaned the magnetic plug-replaced it and put in 2 qts of VALVOLINE HIGH PERFORMANCE gear oil ---SAE 80w-90.I left the level right to the top.Should i leave it now or REMOVE SOME TO LOWER THE LEVEL.There seems to be a few different opinions on this part .

When I did my Front diff. I opened the fill plug first to see where the level was. So, I pulled the fill plug out , and fluid started drizzling out. So I filled it right up to the plug as thats where it was from the factory.

Ok 2MuchFun-Thanks a lot.That's exactly what i have done -so i guess i will leave it like that.Got the Rear Diff. done yesterday and you were right on the money AGAIN about the condition of these fluids.The rear was Almost as disgusting as the front was in terms of QUALITY.Drained and re-filled with 4 QTS of Castrol 75W-90.I can't find the brand names you guys mention on here and am not sure they are avail.in Canada.Valvoline and Castrol seem to be everywhere so i used them.


I guess ALL my fluids now except for brake and rad are done.OIL,TRANNY,FRONT and REAR DIFF.TC DMAX posted his scheduled maintenance list and he mentions the TRANSFER CASE.


Here's another ROOKIE question.Does the 2002 Silverado HD automatic Allison-with the push button 4x4 shifter have a TRANSFER CASE?If so--where do i locate it?

burntb4,


I'm not familiar with the Castrol gear lube you mentioned, the only caution is that it be the synthetic type with the appropriate service API on the container for the Eaton locker which I believe your truck has, but that's not a 100% sure thing.


Inside your glove box on the lid is a card with the VIN and all the RPO codes for equipment installed on your truck when it was built. Check the data card and look for the "G80" code, if you find it that means you have the Eaton locker rear differential.


I don't think the front differential requires synthetic except in extreme cold conditions according to GM. Most who do their own are putting the synthetic in the front as well. One caution is that your truck may have the wrong color breather cap installed on the front axle to handle the synthetic oil, it needs to be the white cap or the synthetic gear lube will "eat it" away.


All four wheel drive vehicles have a transfer case, not all of them have a two speed high/low function. The transfer case is mounted on the rear of the transmission in front of the tailshaft housing where the rear driveline is. It's the large case that the front driveline comes out of and it has a drain plug and fill plug much like your differentials.

I had a "KNOWALLABOUTTRANNY' kind of neighbor come by when i was cleaning my truck and started talking to me about watching me doing my own service.A lot of what we discussed was consistent with what i have read here regarding DIY service,and he was impressed.


One thing he mentioned that i have not seen is in reference to the transfer case.I told him that was the last job for me to do and he advised AGAINST it and suggested i take it to the dealer to get it done because of the MAGNESIUM content of the TC--and that if i nicked or damaged it the road salt would really do damage in a short time.he says the dealer has the right tools and the spray to re-do the TC after service.I did crawl under to check out the TC-looking for the drain and fill plugs and did see the WARNING on it.


Any comments about this topic??

I picked up my '04 DMax last weekend and heard a lot of talk on this forum about low oil levels in the rear diff.


According to the manual that came with the truck, the oil in the rear diff should be between .5"-0" below the fill hole when the truck is on a level surface.


It took nearly two quarts to bring it to that level!


I used the Mobil-1 75-90 Synth to top it off. I'm not towing right now, so I'm going to drain &amp; refill with the Mobile-1 at 4-5000 miles.


Regarding which oil to use. From what I understand the Magnuson-Moss Warranty Act precludes any manufacturer from requireing their OEM brand of lubricant to be used if an equivalent exists. I asked AutoZone which oil was indicated for the rear diff - the computer was very specific - year, make, model, engine, 2WD or 4WD, 2 or 4-wheel steering ... end result = 75-90 WT Synthetic Gear oil. I don't recall if anything was mentioned specifically about the locking rear diff.


Perhaps GM ships these trucks low on diff oil to facilitate break-in...?

Another newbie question. I am concerned with replacing the original gear oil in the front differential with synthetic. I was told mixing the two are like oil and water. I ordered the fluid kit from GMDieselTech.com. Do I need to flush out the front diff. to keep the old non-synthetic lube left in the diff. from mixing with the new synthetic? If so how do I flush out the diff?

My question is why do we need to use synthetic?


The 14 bolt has been humming along for years with no synthetic in it....the front doesn't even require it.


So Tech guys.....my question is Why?

Well I'm not one of the Dmax tech guys, but if you're talking about the G80 locker...


How about because Eaton wants it that way?


How about because if you don't use it and have a failure, your warranty could be denied?


How about because synthetics have the ability to provide better lubrication to the components, with an increased resistance to breaking down, through a wider temperature range?


And as far as the front is concerned, synthetic is recommended for cold climate operations, but the other part is that the front axle is not subjected to the load that running on only the rear differential can create on that unit.


Just a couple of my thoughts from a tech, just not a Dmax tech...http://www.dieselplace.com/forum/smileys/Embarrased.gif

Just changed over to mobil 1 synthetic in front and rear on my truck and wife's Yukon.


The Yukon shows a G80 code for the rear end, I just got to wondering if this might need an additive. I know this is a smaller rear end and all, but is it still an Eaton and not require the additive like our trucks? Anyone have any idea?

Well I'm not one of the Dmax tech guys, but if you're talking about the G80 locker...


How about because Eaton wants it that way?


How about because if you don't use it and have a failure, your warranty could be denied?


How about because synthetics have the ability to provide better lubrication to the components, with an increased resistance to breaking down, through a wider temperature range?


And as far as the front is concerned, synthetic is recommended for cold climate operations, but the other part is that the front axle is not subjected to the load that running on only the rear differential can create on that unit.


Just a couple of my thoughts from a tech, just not a Dmax tech...http://www.dieselplace.com/forum/smileys/Embarrased.gif





The only thing you said that made any sense and was worth typing was the temperature range statement. The rest sounds like barfed back Chevy propoganda....Thanks for trying though.

The only thing you said that made any sense and was worth typing was the temperature range statement. The rest sounds like barfed back Chevy propoganda....Thanks for trying though.





It's the old caveat; "If all else fails, read the directions..."

lakingslayer, your diff kit will be to your soon!


Synthetic is used in about every diff out there now. Has better wear charecteristics, cooling, and proper additives for the G80. No more then how much these need to be serviced, its not worth cheaping out on lube..

Thanks Eric.

And some information from Hoot on the subject. Not going to opinionate on it just link so people can find and make thier own decision.





http://www.dieselplace.com/forum/forum_posts.asp?TID=3487&amp;PN=1