Maint. Time... Transfer Case and Axles

[Mkos1980]

Originally Posted by LETHAL WEAPON

Hey Brian...any reason why my truck doesn't have a g-80 locker in the rear, seems like I'm the only member here that has an open rear...no g-80 in the RPO codes either

Mines an open as well.

[D.Camilleri]

moved to maintenance and fluids forum

[ChevyBowtie]

Originally Posted by Adrexco

Use a synthetic Dexron VI for the transfer case. I used Valvoline Dexron VI Automatic Transmission Fluid. It's a full synthetic. Use 3 quarts and fill it through the speed sensor. Many have used the "over fill" speed sensor method to get an extra quart into the transfer case.

For the differentials, also use a synthetic gear oil. The service manual calls for an SAE 75w-90 Synthetic, they spec this for fuel economy. If you tow heavy it's better to use the SAE 75w-140. I used Lucas full synthetic, but wasn't so happy as there was some contaiminates in the bottom of the gallon container after I pumped them empty. I called and wrote Lucas, but never got any responce back. It could be all the red colored blobs were additive, but I was never able to confirm it with Lucas.

Couple of questions on this
1. is the speed senor, on the top back side of the transfer case?
2. filling the fluid up to this point won't hurt the transfer case?
Thanks

[306LBZ]

Originally Posted by ChevyBowtie

Couple of questions on this
1. is the speed senor, on the top back side of the transfer case?
2. filling the fluid up to this point won't hurt the transfer case?
Thanks

Guys that overfill it through the speed sensor use engine oil when overfilling. Plenty of people do it without any problems, personaly I dont, I stick to transyd(torquedrive for now though). There might even be a study if I remember right somewhere online using 5w30 engine oil I believe in the TCase. I would suggest to be careful when your removing that sensor if you go this route. I've seen a lot of threads on here with guys having issues with this sensor and its possible some of these trucks have had guys removing that sensor before having the issue. I dont know for sure but its a good possibilty

[Dmax 5th Wheel]

I just filled the T case from the fill hole. Got a hand pump & pumped until fluid started to come out. Easy & quick to do it this way. It took a bit over 1.5 quarts. I used the last of the Dexron VI fluid I had laying around.

[ChevyBowtie]

Perfect thanks for info Guys!!

[auwing]

Originally Posted by heymccall

Just be CERTAIN to not use any gear oil labelled for use with positraction or limited slip axles, in the rear differential. Synthetic GL-5 only, or your G80 locker WILL chatter, or, not engage correctly.

Except the only Mobil 1 75-90 to be found says LS on the label. Is this marketing of a product good for all applications?

[Dmax 5th Wheel]

Originally Posted by auwing

Except the only Mobil 1 75-90 to be found says LS on the label. Is this marketing of a product good for all applications?

GM says to use a GL-5 gear lube, & most GL-5 gear lubes that iv seen all say LS on them.

[dnewton3]

I shouldn't be shocked; I'm quite used to the mis-information and dis-information that abounds on this site ....


Here is what I posted from 5 years ago about this whole diff fluid thing:

Originally Posted by dnewton3

Originally Posted by dnewton3
Regarding the "need" for "synthetic" fluids in respect to the front/rear differentials, here is some information. The GM spec 9986115 was PRIMARILY developed so that a GL-5 fluid could be used to help improve fuel efficiency. Further, cold weather and thermal oxidation issues were noted. This basically means GM was looking for a fluid that helped corporate fuel economy efforts, and didn't evaporate quite as fast. The goal here was to get a fluid that could last for longer service intervals (I.E. - not be changed as often!) It has NOTHING to do with the fact that "synthetic" is REQUIRED for safe operation, it just happens to provide longer service life. Here's one quote of proof:

"Document Number : 9986115
Publication Date : 2003-12-01 00:00:00.0
Status : CURR (Current MB)
Organization : General Motors North America
1 Scope This specification describes an axle lubricant to replace previous lubricant 9985290 and 9985182. This axle lubricant, suitable for car and truck axles, exhibits improved fuel efficiency, lower axle temperature operation, and improved thermal stability."


Further, read this:


[Note from Michael Asmussen, Torque Control Products Division of Eaton Corp.]

"Automatic Locking Differential Lubricants.
We recommend the following lubrications for our locking differentials:
1)Texaco 2276; Synthetic 75 W90; Gm Part # 9986115
2)Texaco 9622; Mineral based 80W90; GM Part # 9985290
3)Texaco 2080; Synthetic 75W140 (heavy duty applications); GM part # 9985991
Note - All of the above lubes are preblended with friction modifier. No additional modifiers are necessary or recommended. As far as other lubes are concerned, any standard GL 5 lube will work, but the units perform optimally with the three listed above.


Now you will note that the above quote is from Eaton Corp., the manufacturer of our differentials in our trucks. Here, there is specific reference to the fact that they show both conventional AND synthetic fluids meet the engineering standards for the Eaton differentials. There is specific reference to GL-5 fluids.

You see, GM spec'd out the 9986115 "synthetic" fluid (what we all call grape juice) because it was a FUEL ECONOMY issue, not a warranty issue. This "synthetic" fluid allows for a longer service use, before it has to be changed. But ANY GL-5 Fluid will work and that's STRAIGHT FROM THE MANUFACTURER. There are even references from both Castrol and Mobil that their fluids meet the GL-5 standard as well.

The differential maker (Eaton) notes that ANY GL-5 fluid will work.

The reason GM specifically states to NOT add FM (friction modifier or commonly called L/S additive) is because the GM Fluids (in this case, 9986115) AREADLY HAVE THE FM IN THEM! If you purchase a GL-5 fluid that does not contain FM, you're going to want some in there. That is because the clutch pack WILL chatter if there is no FM. Many (but not all) of today's synthetics already have the FM in there (Amsoil, Mobil 1, others). Many dino fluids do NOT have the FM added. The FM does not cause clutch chatter; used in small doses, it is to eliminate the chatter. However, if you overdose the FM, it can actually invert part of the add-pack chemistry and have the opposite effect, so adding in FM in very small quantities (a few ounces at a time, then driven for a few hunderd miles between each trial) is often a good idea.

So you can use synthetic or dino GL-5, but you may or may not have to add FM, depending upon product.

[dnewton3]

And don't get me started on the bovine-poo about using 3 quarts of engine oil in the transfer case ...