Diff Gear oil 90 or 140w?

[Mikey]

Anybody know the best weight to run in the diff?
Manufacturer calls for 90w. I heard the dodge's manufacturer recommends 140w.
Thoughts?
I just spun a wheel bearing and was wondering if the 140w i am running had anything to do with that.
Thanks for the help!

 

[Whitetail Addict]

http://www.duramaxdiesels.com/forum/showthread.php?t=8618

 

[Noreaster]

90w is fine for normal driving, use the heavier stuff if you tow alot
the axles in GMs & Dodges are made by AAM

 

[DougSmith]

I would think you may need to figure out why you think the weight would help you out. Thicker lube does not equal better lubrication.

Thicker lube will run hotter due to fluid friction. I would come from a different angle. Try better lube.

I have found that Schaeffer's full synthetic 75w-90 with molybdenum will lubricate better and keep any diff cooler and therefore eliminate bearing failure.
Try it, what do you have to lose? You already found what does not work, try something that does.

www.schaefferoil.com and read up on the specs. I am a believer and just changed all my fluids over to Schaeffer's. Best I have seen by miles.

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[RKTMech]

We use mobile one 75w-90 LS syn gear oil, never had an oil related issue yet, "knock on wood"

 

[Whitetail Addict]

We use mobile one 75w-90 LS syn gear oil, never had an oil related issue yet, "knock on wood"

I used the Mobil 75W-90 in my truck as well.

 

[Mikey]

Amsoil 140w was in it w/ friction additive.
I think something else failed. Upon taking the axle and then the diff cover off Found lots of metal. Where did it come from?
Now I need to figure out what went wrong and need to have my rear end rebuilt. Anybody know someone good in so cal? I have factory GM manuals but would prefer experience to help me rebuild as I am concerned about shimming and other stuff like that. I am also considering going to a 3.42 gear.
SEE PICTURES.
Thoughts Please.
Thanks!

 

[05dmaxdriver]

running 75-90 syn by Delo all good here .

 

[DougSmith]

Why do you think you need heavier weight fluid? It is certainly not for lubrication or prevent heat.

Heavier fluid will run hotter and does not lubricate better. That will lead to failure. Plain and simple.


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