Clarification on Front & Rear Differential Lubes

DgTerrell

Original poster
Member
May 22, 2012
25
I know this subject has been played out a million times on here, and I've read over a ton of threads about it, but I want to be 100% sure. I plan on changing the Transfer Case fluid, and the rear & front differential lubes this weekend. This is pretty much my first time at playing mechanic and I want to make sure I buy exactly what I need. I have a Trailblazer 4.2 I6 4x4 with no G80. So I do not need the limited-slip additive, right? I'm looking to buy either Amsoil Severe Gear 75w-90 (product code: SVGQT-EA; will that work for me? It says it has additive in it, but you can buy an additional 4oz.) or the Mobil 1 non LS 75w-90. I'm having a hard time finding any of the Mobil 1 that doesn't have the LS additive. I need 3 quarts of the lube, 1 up front and 2 in the rear, right? I know I can only use the Auto-Trak II GM# 12378508 for the Transfer Case.

One more thing. Does anybody know what the torque specs are for theses 3 projects?

I really appreciate any help, and I apologize for bringing up something that has already been discussed. I just see most of the discussion is usually with people who have the G80.
 

Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
You can use the Mobil 1 with the LS additive. I have the G80 and use it in both the front and rear and there is no G80 in the front.

The front and rear differential fill and drain plugs (your rear diff doesn't have a drain) are 24 ft. lbs. The diff cover bolts are 30 ft. lbs.

The transfer case drain and fill plugs are 20 ft. lbs.

These torques are from the 2003 Service Manual, I believe the 2006 is the same.

Also, make sure you can remove the fill plug before removing the drain plug.
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,665
I will 2nd the motion to just use the LS Mobil 1. I used it in both diffs without issue.
 

Shdwdrgn

Member
Dec 4, 2011
568
As further proof to always check the fill plug first... my sister and I did differential and transfer-case fluid changes yesterday on our '97 blazers. Mine went nice and smooth... not so much for her truck. She got the fluid drained out of her front differential, then discovered that the shop which did her change last time had severely over-torqued the fill plug. I could not find any way to tap it loose, and ended up rounding off the bolt somewhat. Her neighbor was finally able to remove it using his air-hammer, but it was still a lot of work for removing a bolt that was just put in a year ago.

By the way, if someone needs a quick source for replacement drain/fill plugs... We got a new bolt from Ace hardware. They had a great selection of standard and metric drain plugs, when none of the local car-parts places had the right size.
 

Wooluf1952

Member
Nov 20, 2011
2,663
Milwaukee, Wisconsin
Shdwdrgn said:
By the way, if someone needs a quick source for replacement drain/fill plugs... We got a new bolt from Ace hardware. They had a great selection of standard and metric drain plugs, when none of the local car-parts places had the right size.

I'm really hoping to avoid that problem, but good to know.

Dealer would probably only have it with a new diff. :wink:
 

fj4072

Member
Jun 1, 2012
13
Wooluf1952 said:
You can use the Mobil 1 with the LS additive. I have the G80 and use it in both the front and rear and there is no G80 in the front.

The front and rear differential fill and drain plugs (your rear diff doesn't have a drain) are 24 ft. lbs. The diff cover bolts are 30 ft. lbs.

The transfer case drain and fill plugs are 20 ft. lbs.

These torques are from the 2003 Service Manual, I believe the 2006 is the same.

Also, make sure you can remove the fill plug before removing the drain plug.



New to GMT, transplant from the other site, glad I found the core group again!! I can't remember for the life of me how to find out if I have limited slip in the rear. Markings in the glove box is ringing a bell?????
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR
fj4072 said:
New to GMT, transplant from the other site, glad I found the core group again!! I can't remember for the life of me how to find out if I have limited slip in the rear. Markings in the glove box is ringing a bell?????
Glad you found us as well. Ghost town over there now, eh?

If you have a Chevy, non SS, you cannot have LS. The G80 (glovebox sticker) is an automatic locker, not limited slip. It *does* have clutch plates inside that assist activation of the locker feature, but they are not the kind that normally chatter or make noise that LS additive is supposed to cure.
 

fj4072

Member
Jun 1, 2012
13
the roadie said:
Glad you found us as well. Ghost town over there now, eh?

If you have a Chevy, non SS, you cannot have LS. The G80 (glovebox sticker) is an automatic locker, not limited slip. It *does* have clutch plates inside that assist activation of the locker feature, but they are not the kind that normally chatter or make noise that LS additive is supposed to cure.



Roadie!!! Missed you guys, yep sure a ghost town over there heh heh. No clue what happened, doesn't matter, just glad to be in good hands here. Thanks for the knowledge. Still owe you several beers, when you coming up to try the Rubicon up here in N. CA?:thumbsup:
 

The_Roadie

Lifetime VIP Donor
Member
Nov 19, 2011
9,957
Portland, OR

dingle

Member
May 26, 2012
59
Dumb question here. Having the Saab I do have the limited slip rear end. I bought a quart of Mobil one LS gear lube. I'm assuming that the LS means it has the limited slip modifiers but I wanted to make sure before I added it to the rear differential. I know no matter if it does our doesn't have the additive it will work in the front diff. I want to check the levels before the weather gets bad.
 

RayVoy

Member
Nov 20, 2011
939
That is what the LS stands for, you should be good to go.
 

jeffro312

Member
Oct 4, 2012
442
East Haven,Ct
dingle said:
Dumb question here. Having the Saab I do have the limited slip rear end. I bought a quart of Mobil one LS gear lube. I'm assuming that the LS means it has the limited slip modifiers but I wanted to make sure before I added it to the rear differential. I know no matter if it does our doesn't have the additive it will work in the front diff. I want to check the levels before the weather gets bad.

Are you just topping off?? Mind as well change the fluid out while its not too cold out... its a fun job. I promise
 

dingle

Member
May 26, 2012
59
I bought it so when I check the levels if they are low I can add and fill. It only has 66k miles on it so I didn't think it was necessary to change right now that's why I was just gonna check and add it needs it
 

Billdaman

Member
Jan 19, 2012
32
DgTerrell said:
I know this subject has been played out a million times on here, and I've read over a ton of threads about it, but I want to be 100% sure. I plan on changing the Transfer Case fluid, and the rear & front differential lubes this weekend. This is pretty much my first time at playing mechanic and I want to make sure I buy exactly what I need. I have a Trailblazer 4.2 I6 4x4 with no G80. So I do not need the limited-slip additive, right? I'm looking to buy either Amsoil Severe Gear 75w-90 (product code: SVGQT-EA; will that work for me? It says it has additive in it, but you can buy an additional 4oz.) or the Mobil 1 non LS 75w-90. I'm having a hard time finding any of the Mobil 1 that doesn't have the LS additive. I need 3 quarts of the lube, 1 up front and 2 in the rear, right? I know I can only use the Auto-Trak II GM# 12378508 for the Transfer Case.

One more thing. Does anybody know what the torque specs are for theses 3 projects?

I really appreciate any help, and I apologize for bringing up something that has already been discussed. I just see most of the discussion is usually with people who have the G80.

I put Mobil 1 in My diff after a lot of study. There is an excellent White paper on gear lubes that was done by Amsoil with lots of test results. Very thorough. Obviously they won, but the results were close.
 

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Fire06

Member
Dec 18, 2011
7,223
I have been using the Amsoil since I changed the F & R diffs oil out and have had no problems.
 

TangoBravo

Member
Dec 5, 2011
208
Fire06 said:
I have been using the Amsoil since I changed the F & R diffs oil out and have had no problems.

I use amsoil as well. Have done so since the TB had about 10,000 miles on it. With the exception of the transfer case everything is amsoil. Haven't gad any problems yet, and sincr I am also an Amsoil dealer I don't expect any issues either. LoL
 

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