One Gear Oil To Rule Them All

[Okie69]

I’ve been reading threads and I’m hoping to get some more recent opinions. I’m at the stage where I’m starting to think about gear oil. It looks like a lot of y’all are running synthetic 75w90 on the front, rear, t-case, and transmission. I like the sound of using the one oil for everything to simplify things. The question is about the reactions between the yellow metals and some of the oils.

Some of the posts I’ve seen say it’s not anything to be worried about on new synthetics. So I guess the question is what brand/type is everyone using? Or am I better off going with a couple of different ones?

 

[Yeller]

On my stuff that uses 75/90, 80/90 or similar I use plain ol dino based oil. However if I’m out and have synthetic on hand it will get the nod with no discretion which gear box it is going in. I’m not a snob on lubricants except on modern tight tolerance stuff then it’s exactly what it asks for and if synthetic it gets Amsoil.

My one exception is steering. I put Amsoil tractor fluid in all of them. A few of the big name manufacturers frown on it and say it’s too thick. I’ve never had it cause a failure and had it solve a lot of noise and cavitation issues.

 

[JB Fab]

Don't use a GL-4 or GL-5 Gear-lube in a Dana 20, the sulphur based pressure additives etches the "yellow metal" causing more friction than it was designed for, this causes the one thrust washer that is under the heaviest load to run hot, and in worst case to spin and ruin the case/idler gear

 

[Spaggyroe]

For the folks running an Atlas 2 transfer case....
Advance adapters recommends only Redline full synthetic, 75W-90 API GL-4

Redline says it's safe for brass synchro's, as it lacks the sulphurs found in most GL-5, so I can't imagine it not being ok for the Dana 20 as well.
Hang on to your shorts when you go to buy it though, as it's ~$18 a quart.

 

[Yeller]

All of the atlas’s that I’ve installed all came with Amsoil Syncromesh.

But I’ve had them recommend the above redline and 10/30 synthetic motor oil

 

[Okie69]

Interesting responses so far. Let me ask this, what does “the book” call for for each of the components in question? Actually what is the modern equivalent of what the book calls for?

This is from the Chilton manual I have:
Manual transmission


Front and rear axles


Transfer case

 

[Okie69]

Also, here’s the capacities chart if anyone is interested.



I wonder why some years call for more rear oil?

 

[DirtDonk]

I’ve always taken them as accurate but never used any other way but the good old “manual verification method” on mine.
Meaning some of the differences are probably discrepancies and mistakes in the writing of the manuals, while the proof is in the pudding so to speak.
When oil is within fingertip distance, or drips out the site plug hole, it’s full.

 

[Spaggyroe]

All of the atlas’s that I’ve installed all came with Amsoil Syncromesh.

But I’ve had them recommend the above redline and 10/30 synthetic motor oil

We’re they older installations?

I installed mine ~18 months ago. The installation docs (dated 6/27/18) call for redline (plus, that’s what AA shipped with it).

 

[bronco italiano]

Swepco 201 is the only gear oil I use. Found nothing better yet. No hocus-pocus Amsoil magic, just well formulated gear oil.

 

[Yeller]

We’re they older installations?

I installed mine ~18 months ago. The installation docs (dated 6/27/18) call for redline (plus, that’s what AA shipped with it).

17 was the last new one I installed.

Swepco 201 is the only gear oil I use. Found nothing better yet. No hocus-pocus Amsoil magic, just well formulated gear oil.

I don’t take all of their coolaide too serious. I just have faith the products are consistently produced and are of good quality that I can usually get delivered overnight at a reasonable price. Swepco makes some nice stuff, have run plenty of their 250wt gear oil in u4 cars.

I’m stepping back, I think this is all good discussion but not answering the OP’s question.