Fluid Question

[jeremywatco]

Hi there,
Got my C4 and Dana 20 rebuilt last month. Finally got them back in the bronco.

Shop said any fullly synthetic atf in the trans. I was thinking Merton V but my store only had Mercon LV in synthetic. Think that work?

For the transfer case I was again going to run a full synthetic 75w90 but the only full synthetic at my local store across all brands has the friction modifiers added. Will those harm the transfer case?

 

[Kalex]

Not saying anything about what’s correct versus not. My C4 is getting rebuilt now and I did my transfer case. I plan to use Amsoil Severe duty 75-90 gear oil in my transfer case and my transmission builder wants only hydraulic oil in my transmission. I don‘t know the oil yet as it‘s not finished yet. He will tell me when I pick it up. Good luck with whatever you decide.

 

[JB Fab]

Use 50Wt Valvoline VR2 motor oil in the Dana 20, do NOT use 75-90, or any synthetic. The pressure additives in Hypoid gear oil are Sulphur based. the Sulphur based pressure additives will etch the the soft 'yellow metal' of the idler gear thrust washers. etching=friction, friction=heat. That is the same reason you don't use gear-lube in a manual transmission that has brass thrust washers or synchros. Failure of the thrust washer can also damage the thrust surface of the idler gear, many time it is not noticed and reinstalled resulting shortened service life of the new thrust washer. worse case is the thrust washer has enough friction to shear the anti-rotation tab and spin, that ends with the transfer case itself being damaged. in synthetic has the same viscosity rating but thinner pour point, it has a tendency to make our D20s noisy, there is nothing close tolerance or high heat about our D20s, synthetic is the wrong tool for the job.
Good replacement gearsets are getting harder to find, a majority of us are running significantly more torque through our D20s than they were designed for, there is someone that machines the idler gear to accept a bearing (eliminating the thrustwasher BS) . if you are interested talk to Adam at the the Overdrive Guy, (360) 256-3843.
Then you can run 75-90 without a problem...........

 

[Kalex]

Thanks Jon. I will change direction for sure on my transfer case. My transmission will have thrust bearings all throughout as he machines the parts to hold the bearings. I just stopped by and saw the process, very cool.

 

[JB Fab]

Sorry, I have zero expertise in automatic transmissions, I will have to leave that question to someone else.....

 

[jeremywatco]

Thanks all. Talked to my builder today. He said for my transfer case to run 75w90 synthetic and for my c4 to run a good quality full synthetic. Doesn’t matter if it’s Mercon V or LV just said needs to be synthetic. So I guess I answered my own question, call your builder and ask what your specific rebuild needs

 

[jamesroney]

Thanks all. Talked to my builder today. He said for my transfer case to run 75w90 synthetic and for my c4 to run a good quality full synthetic. Doesn’t matter if it’s Mercon V or LV just said needs to be synthetic. So I guess I answered my own question, call your builder and ask what your specific rebuild needs

Wow. You just ignored some of the best advice from one of the PREMIER transfer case resources on the planet…and took advice from a moron that you gave money to.

@JB Fab wasted his extremely valuable time to provide detailed justification for WHY you don’t want to use an API GL-5 modified lubricant in a gearbox with yellow metal.

I have no words…

 

[ntsqd]

As I recall the original spec for the transfer case called for Engine oil, NOT gear lube. For the very reasons that JB Fab mentioned.

You're not required to take the advice that you ask for, but when you don't it makes folks less and less likely to want to help.

 

[4xfun]

How old is your builder? The issue with Sulphur and brass is a known issue to the older generation that should not be taken lightly. Synthetics are great for some uses, but your transfer case was designed before synthetics were available. Use something similar to Dana's original specification. Take a look at Novak Conversions website. Their recommendation is:

When filling your Dana transfer case with gear oil, we recommend that you select a conventional mineral oil or a para-synthetic in lieu of a full synthetic oil. Properly assembled manual gearboxes do not have the thermal strains seen by combustion engines or hypoid gears. Synthetic fluid in these gearboxes, while not harmful, is probably an economic waste.

Hypoid gear oil is sulphurized higher than transmission oil and can be mildly corrosive to the non-ferrous alloys used for bushings and thrust washers in these transfer cases.

An 80W-90, API-GL5 or MT-1 rated fluid is very good.

 

[jamesroney]

How old is your builder? The issue with Sulphur and brass is a known issue to the older generation that should not be taken lightly. Synthetics are great for some uses, but your transfer case was designed before synthetics were available. Use something similar to Dana's original specification. Take a look at Novak Conversions website. Their recommendation is:

When filling your Dana transfer case with gear oil, we recommend that you select a conventional mineral oil or a para-synthetic in lieu of a full synthetic oil. Properly assembled manual gearboxes do not have the thermal strains seen by combustion engines or hypoid gears. Synthetic fluid in these gearboxes, while not harmful, is probably an economic waste.

Hypoid gear oil is sulphurized higher than transmission oil and can be mildly corrosive to the non-ferrous alloys used for bushings and thrust washers in these transfer cases.

An 80W-90, API-GL5 or MT-1 rated fluid is very good.

Gotta be careful here. API-GL5 is not all the same. The old Extreme Pressure additive package to achieve GL5 is known to destroy yellow metal. This is why there is so much Misinformation out there. MANY revised GL5 packages are now safe for yellow metals, but SOME GL5 synthetics still have the sulfur additive. And some GL5 synthetics never had the sulfur. So the statement that Synthetic GL5 is “good” is only true sometimes…but is becoming more true as more manufacturers revise their blends. Most of the good brands are now including “safe for yellow metal” on their labels.

SAE 50 motor oil never contained a sulfur package, and is specified by Ford and for use in the Dana-20. but of course it has limited EP properties. Jeep and IH specify gear oil in their functionally identical Dana-20.

It’s getting harder to find dinosaur oil in GL-4, (but you can still get it for your tractor)

 

[Timmy390]

My go to....

CRC Sta-Lube API/GL-4 Multi-Purpose Gear Oil 85W90​

Tim

 

[ntsqd]

My go-to for HD gear oil is Swepco, but I'd honestly have to look to see if their gear lube is yellow metal safe or not. I've yet to need to know that. Lighter duty stuff gets Redline, but again I'd have to look up if yellow metal safe or not.

 

[Kalex]

I just purchased 2 quarts of Valvoline VR1 50W racing motor oil. I didn't see any VR2. Hoping this is acceptable, if not it's not going in anytime soon so I will pivot again if need be.