Transfer case oil recommendation?

[anoblefox]

It has been at least 25 years since I re-sealed the side cover gasket and added new fluid. I searched for an answer here to no avail. I seem to remember the repair manual specified 50W non-detergent motor oil, am I correct? We recently moved and my repair manual is buried somewhere in a shipping container.

 

[reamer]

Believe its 30W

 

[gr8scott]

It has been at least 25 years since I re-sealed the side cover gasket and added new fluid. I searched for an answer here to no avail. I seem to remember the repair manual specified 50W non-detergent motor oil, am I correct? We recently moved and my repair manual is buried somewhere in a shipping container.

You are correct.

 

[Jedeka]

I’m having trouble finding 50W non-detergent oil that is not GL-5 rated.

 

[Broncobowsher]

90(ish) wt gear oil.

Ford bought gear boxes from a lot of suppliers. The same gear box used in other applications used regular gear oil. For some strange reason Ford had this thing about using motor oil in transmissions. Probably a hold out from the Model T days when it was all one oil.

These vintage gear boxes are pretty simple are fairly crude. Doesn't take anything special to keep them lubed and running forever. 50wt motor oil, 90wt gear oil (which are the same viscosity but different scales, think Celsius and Ferenheit) both work. Since the 80s most transfer cases run ATF for better fuel economy, there are a few reports of long term use of ATF that were fine.

 

[Lawndart]

If you really want to stick with 50W mineral, one source is your local general aviation airport. They should have Aeroshell 100 (50 weight) available. Or just order it online. This is what I run, however I have easy access to it.

 

[badasstrapper]

I use 50w valvoline racing oil

 

[EPB72]

I use 50w valvoline racing oil

+1 for many many years..

 

[anoblefox]

Went to airport and bought aeroshell 100, done deal.

 

[JB Fab]

If you use a motor oil it should be non-detergent. Most motor oils now days is detergent, meaning is has surfactants that keep contaminants suspended so they can be filtered out in a pressurized lubrication system that has a filter. Non-detergent allows the contaminants to precipitate out and fall to the bottom where (hopefully) they will not be an issue.
IMHO 50wt non-synthetic manual transmission fluid is preferred (MT-1 rating). Anything with a GL-4 or GL-5 Like gear-lube has sulphur based pressure additives that affect the brass on the idler gear thrust washers.
The sulphur etches the the thrust washers increasing their friction against the idler gear, causing heat, reduced service life and sometimes failure of the thrust washer.

50wt MT-1 is usually found at truckstops, as it is used in over the road trucks with manual transmissions (for the same reason).

 

[JB Fab]

I use 50w valvoline racing oil

Way better than using gearlube, plus it has lots of zinc (yellow metal friendly wear additive)

 

[savage]

Way better than using gearlube, plus it has lots of zinc (yellow metal friendly wear additive)

I use that oil to 50w valvoline racing oil.

 

[DirtDonk]

I agree with all of the above. But I'm pretty sure that the manuals have not stated "non-detergent" for a very long time. However, the ones I used in the beginning did state that so I've been a Valvoline Racing Oil user for many years.
But I've also used 75w/90 synthetic gear oil that said it was safe for soft metals (Redline brand) so I could use it in all four locations. The two diffs, the transmission and the t-case.

I've heard the thing about 50w and 90w being the same, and certainly can't argue the science. But I hated using 90wt for the transfer case because the old Sta-Lube hand pump I used to use was so hard to pump with it! The 50wt motor oil and the thinner synthetic were much easier to pump in.
With modern containers that might not be as big an issue. But it sure was for me and my tired arms!

Paul

 

[reamer]

Right from my 1973 Bronco owners manual

 

[NateMob]

Right from my 1973 Bronco owners manual

Does it show the amount of fluid in any of the other columns?

 

[reamer]

2 3/4 pts (Pints) (1.375 quarts)

 

[blubuckaroo]

Our '77 has the original transfer case, and it's never been opened up. It's got over 300k miles on it. It's had SAE 50 Valvoline Racing oil in it since the first oil change.
That is except for the time the adapter seal went out and filled the transfer case with Dextron transmission oil. That incident must not have hurt anything. That was over 20 years ago.

 

[NateMob]

2 3/4 pts (Pints) (1.375 quarts)

Thank you.

Our '77 has the original transfer case, and it's never been opened up. It's got over 300k miles on it. It's had SAE 50 Valvoline Racing oil in it since the first oil change.
That is except for the time the adapter seal went out and filled the transfer case with Dextron transmission oil. That incident must not have hurt anything. That was over 20 years ago.

Hell of an endorsement. Just ordered 3 quarts for my newly rebuilt D20!