Transfer Case Fluid? Quick Answer Appreciated!

[BronCowie]

Urgent Question

My Bronco is in a local family owned transmission shop having my C4 rebuilt. In their research they think they know what fluid should be in there, but want confirmation... I have no idea.

What type and weight should be in my Dana 20 transfer case?

 

[tabyers]

Much research done, many oil reps called. Original Ford shop manuals for my 69 said sae 50 so that's what I run. Conventional 50 wt. I'm sure there's an opinion for each individual Dana 20 ever produced though, so I hope I didn't make a mistake admitting to it. There are probably a lot of different things that it couldn't tell the difference in though. I did have to order it from O'rielly's too.

 

[gr8scott]

X2, Bronco Dana 20 transfer case takes 50 weight oil.

 

[tabyers]

Yay !

 

[Broncobowsher]

Original fill is 50wt motor oil. Many fill with gear oil. Anything from 75 to 140 weight will work. The generic answer is 90wt.

The dana 20 is a very simple gear box. It is not fussy about oil at all. So long as there is oil, just about any oil, preferably clean oil, it will be happy.

Factoid, gear oil and motor oil are on different weighting scales. 50wt motor oil is the same viscosity as 90wt gear oil.

 

[DirtDonk]

Might be, and I've heard that reported here and there many times. But try to pour 50wt motor oil out of a can, then try pouring 90wt gear oil. I'm pretty sure I see a difference.
But try that same trick with one of those old Sta-Lube container pumps and you'll KNOW there is some kind of a difference between the two oils!

My arm gets tired just thinking about pumping 90wt with that old thing.%)

Paul

 

[blubuckaroo]

Urgent Question

My Bronco is in a local family owned transmission shop having my C4 rebuilt. In their research they think they know what fluid should be in there, but want confirmation... I have no idea.

What type and weight should be in my Dana 20 transfer case?

You're a guru without an owners manual??:?

 

[BronCowie]

Good discussion guys. I'm going with 80/90 gear oil. Thx!

 

[Pa PITT]

... While reading this ... I'M THINKING hell i've got the wrong oil in mine...
I like the Red 90wt. from maybe Texaco.
... But just a 90wt in my opinion ...

 

[blubuckaroo]

My pay grade is way under that of an automotive oil engineer, so I use what's recommended in the owners manual. SAE 50.
Chances are though if your car gets serviced at a garage lube rack, they're going to replace or top it off with 85W-90 gear oil. And that's only because they don't stock the right oil.

There are a lot of reports on the difference between GL4 and GL5 oils and their applications to differentials and not necessarily to trannys.
Hare's a lot of worthwhile reading on the subject, so you can make your own decision.
http://www.widman.biz/uploads/Transaxle_oil.pdf

 

[DirtDonk]

I agree. When in doubt, go with the factory recommendation unless it's been proven over time to be wrong. And that doesn't happen very often.
I liked the thinner oils myself. So while I did change to gear oil, I went for the 75w/90 because it was very thin and easy to pump into the transfer case.

But as long as you don't mind using two different lube types between the differentials and the transfer case (which really isn't that big a deal for most) then stick with the 50w motor oil for a happy D20.
At one point I had a brochure, or a data sheet that called for 50wt "non-detergent" (racing type) oil. But none of the normal books or Ford manuals calls out that distinction that I've seen.

Paul

 

[ransil]

I ran 50 in the past, winter time made it hard to shift.
due to lack of finding 50 wt easy I switch over to 75-90 mobile 1 synthetic , no issues shifting after the change, it wasn't a show stopper just tight shifting.

 

[Pa PITT]

... I had Mystic 75w in mine for years & I shifted great.
Then when I went to New Mexico with my Bronco .. The clutch went out on my Bronco like 2 days before We were to leave. So I still was working at Chrysler at that time. So the trans mission guy & his helper were my Buds. So they Jumped onto my Bronco & Got me a new clutch .. It was kind of a funny deal .. Those 2 TECHS were in the top 1000 USA Techs. THAT OLD GUYS KNEW EVERY THING ...
... So He thinks my Dana fluid is bad. Because of it's color.. SO He put in new B/G Fluid ... That was not as good as my Mystic ..Which was also new.
Then He replaced my NP435 Fluid it too was my MYSTIC must better .. It was now hard to shift in the cold. & He gave me all sorts of HELL ABOUT PUTTING A GRADE 5 BOLT WHERE A SHOULDERED BOLT WENT.
... He had lost my Special Shoulder Bolt ... But after I got home & was giving my Bronco a service after it's 400 mile of 4x4 on the rochs at the NM ranch..
I found my shouldered bolt .. it had made the entire trip up inside the crossmember . I'd put my hand up there & it moved. When I pulled it out I could not wait to get back to work & give them hell.
... They couldn't believe I got the best of them. FLUID & MY BOLT.
... DON'T WORK TO HARD TO GET AHEAD OF OLD PA PITT..

 

[blubuckaroo]

My D20 has never been opened up other than to replace the intermediate seal. It has around 300K miles on it. All with SAE 50 Valvoline Racing oil.
It has twin stix now, but when it had the "J" shifter, it could shift into and out of 4WD at 60 mph with ease.
I can't understand using anything but the recommended oil. It's available at any good auto parts store. Why take the risk when the real deal works great?

 

[bronconut73]

[My pay grade is way under that of an automotive oil engineer]

Well Blu....you may be surprised to hear that an "Oil Engineer" likely doesn't make much more than you....lol.
A shame but true.
Now, while Blu is usually right about most of this stuff, I will say that modern lubrication technology has eclipsed most any lubricant from the era that our eb's were built.
Having said that, a Dana 20 is not a very demanding TC regarding oil quality. But I say why skimp if really good modern lubes are available. I use 75/90 Red Line synthetic gear lube. The "best" lube manufacturer on the planet. But I can't really afford to use Red Line everywhere in the eb, but with such long changing intervals with the TC verses the engine, it seems like money well spent.
Alright,
off my soap box.
Flame on Blu, lol...

 

[edmedlin]

I use the Lucas 80/90wt (8/9wt label) racing oil in the front, rear and transfer case. I have use it for years in every racing gear box and never had a failure. We use 9" Fords exclusively and the gearboxes are the Brinn type direct drive which is a lot like the D20 with low/high and forward, reverse and neutral on the other stick. It is synthetic and lubes great. Lucas sponsored us and we used all Lucas lubes (free, so why not?). I wouldn't buy their racing spec grease at $90-$100 a tube, but the other stuff is about the same as any other. They also have a high-zinc motor oil that is great on the older motors.