transfer case oil change

[Wolverine]

Hombres:
I have a '73 with a dana 20. The truck was very well maintained but when I checked the tranny oil it was black, so I changed that. Assuming the dana 20 oil was never changed, should I? Looked in the CB forum couldn't find any 'directions.' Nothing on youtube for changing a 20 (specifically). I can probably find the drail/fill plugs, but if y'all know of a video or link I'd appreciate it. And, what gear oil and amount? Thanks in advance.

 

[DirtDonk]

Yes, you should change it for sure. Even if you knew it had been done at some point by the PO, it won't hurt to do it again and is cheap enough to hardly notice in the wallet.

The draining part is easy, as all you do is put a 3/8" drive ratched stub into the square hole of the drain plug on the driver's side of the case, unscrew it and let it come right out.

Pumping new oil into the case is not as bad as on some vehicles since it's pointed to the rear and has some access. But it's still up high enough that on some Broncos using just the old squeeze bottles is problematic so you resort to a pump.

The specified lubricant for all Dana 20's in the Broncos was 50wt motor oil. Yep, motor oil.
All the more reason to change it out in my opinion, since there is actually a shelf-life as opposed to just a mileage life. At some point, it's just old. And if it's been in there 40 years plus, I think it's done it's job and can be retired.

Regarding the use of motor oil, if you used a gear lube in the manual gear box that is not overly thick, and is most importantly, compatible with soft metals like bronze (as in bushings and thrust washers), then you could in a pinch use it in the transfer case too. I happen to use a synthetic 75w/90 in all my boxes. It's nice to have it all the same in all four boxes, so I don't have to think about it and I don't have too many things to know! But it MUST specifically be compatible with this type of box and have the right characteristics. Should say so right on the container.
But it's been proven well over time that the 50wt motor oil does the job nicely.

So when in doubt... Factory specs rule the day.

Paul

 

[Wolverine]

Paul:
Much obliged. Online it mentions Motor craft transfer oil XL12, but I will use your recommendation if you think that is the direction to go? And 2 quarts in a dana 20?

 

[sykanr0ng]

What is going in when I rebuild mine:
Mobil Delvac 1 Transmission Fluid 50, a full synthetic made for splash lubricated manual transmissions.
The Dana 20 is splash lubricated.

 

[DirtDonk]

Hmm, had not seen that stuff. Sounds interesting.

Wolverine, the spec calls for just under 3 pints if I remember.
I'll see if I can find a reference in one of the books.

Paul

 

[Rustytruck]

I use 75/90 Lucas synthetic gear oil which has close to the same viscosity as 50 weight motor oil when measured on the same viscosity meter. I changed to synthetic trying to improve my shifting qualities of my J shift transfer case. its been in my transfer case for 30 years now with no failures.

https://lucasoil.com/pdf/TDS_Lucas-Synthetic-SAE-75W-90.pdf

https://sharena21.springcm.com/Publ...2d889bd3/a61538b4-0cbd-e711-9c12-ac162d889bd1

 

[bmc69]

I recently tried some RedLine MT-90 synthetic in trans and t-case. Whoowhee..what a difference in reduced noise and smoother shifts. I was a total skeptic ....

 

[B RON CO]

Hi, I see you have not been on this forum too long. How about the rest of the rear end fluids. The front end bolts off, but the Ford rear end is no fun.
While you are bonding with the Bronco I would plan on making sure all the grease fittings are greased, and repack the front wheel bearings and check all the brakes and calipers and wheel cylinders are good (for safety).
The fun really never ends.
Good luck

 

[Broncobowsher]

The good thing about these old trucks, they are not real picky about what oil you put in them. So long as it is oil, it will generally work just fine. Motor oil in the engine, gear lube in the gear boxes, they just keep running. Any decent oil today is way better then what it was filled with when new back in the day.

 

[DirtDonk]

And while we're on the subject of maintenance, I might as well mention it. I've got one word for you...
Rear wheel bearings.;D

Can you still contact the PO to see if those were ever changed? New axles maybe? How many miles on the truck?
Reason for all those questions is that, by about 100k miles, you should be keeping rear wheel bearing changes in the back of your mind for the next time you do a brake job or replace the gear oil in the diff.
They only live so long, but have a critical part in your safety and happiness. So my advice has always been, if your Bronco has over 100K miles on it and you don't know if they have ever been changed... Do it.
Soon.

When in doubt, change 'em out.

Paul

 

[Wolverine]

Wow, Paul brings up a great point, bearings. Funny story... back in 1980 I had a '76 F250 Hiboy custom, and I slaved over that thing, including greasing bearings, changing u-joints, ditto with my '76 bronco (R.I.P.) in early 81-82. Fast forward, I lost the religion, bought new trucks, sold after 2-3 years, bought new, so never had to do any upkeep. Having a blast getting under this Bronco. Next up after the dana is bearings. Thanks Paul and all.

 

[DirtDonk]

Haha! Yeah, it's not a job... It's a lifestyle.

Paul

 

[sprdv1]

Agreed.. simple enuf to drain and refill...

Keep it clean...

Yes, you should change it for sure. Even if you knew it had been done at some point by the PO, it won't hurt to do it again and is cheap enough to hardly notice in the wallet.

The draining part is easy, as all you do is put a 3/8" drive ratched stub into the square hole of the drain plug on the driver's side of the case, unscrew it and let it come right out.

Pumping new oil into the case is not as bad as on some vehicles since it's pointed to the rear and has some access. But it's still up high enough that on some Broncos using just the old squeeze bottles is problematic so you resort to a pump.

The specified lubricant for all Dana 20's in the Broncos was 50wt motor oil. Yep, motor oil.

 

[sprdv1]

Wow, Paul brings up a great point, bearings. Funny story... back in 1980 I had a '76 F250 Hiboy custom, and I slaved over that thing, including greasing bearings, changing u-joints, ditto with my '76 bronco (R.I.P.) in early 81-82. Fast forward, I lost the religion, bought new trucks, sold after 2-3 years, bought new, so never had to do any upkeep. Having a blast getting under this Bronco. Next up after the dana is bearings. Thanks Paul and all.

They are a blast man for sure...

and we always hope there's nothing to disastrous that the PO did we haven't found yet LOL

 

[sprdv1]

Paul:
Much obliged. Online it mentions Motor craft transfer oil XL12, but I will use your recommendation if you think that is the direction to go? And 2 quarts in a dana 20?

fill the 20 till it comes out the plug.. Good to go

 

[sprdv1]

The good thing about these old trucks, they are not real picky about what oil you put in them. So long as it is oil, it will generally work just fine. Motor oil in the engine, gear lube in the gear boxes, they just keep running. Any decent oil today is way better then what it was filled with when new back in the day.

Amen to that.. No need to go all out on like the royal purple stuff

 

[sprdv1]

I recently tried some RedLine MT-90 synthetic in trans and t-case. Whoowhee..what a difference in reduced noise and smoother shifts. I was a total skeptic ....

Pricing reasonable for that Bill...?

 

[Kalex]

I just paid $25 and some change including shipping for some Mobil 1 synthetic 75W90(2 quarts). Going to try it after reading this thread. I have 1 through bolt that leaks a little(driving me crazy) so I figured why not change it since I am going to drain it anyway.

 

[Wolverine]

Man, so many choices and y'all are 'guru's so I don't think I can go wrong with any of the recommendations... I bought the Redline MT90 (based on BMC69 comment about reduced noise and smoother shifts). My dana seems to have a slight noise issue, hope this works. Got sidetracked, my aux tank started leaking at the fuel sender. Tried everything to seal, new gaskets, rubber, cork, paper, etc... nothing worked. If I told y'all what finally worked you would probably laugh and I would never hear the end of it. But at least the leak stopped.

 

[DirtDonk]

What kind of noise issue? While the new oil might quiet stuff down, you may also be hearing the main input and/or output bearings starting to get old.

Unless you're talking about the big gear-whine issue when in 4wd maybe? That's normal for any gearbox using straight-cut gears.

But with luck it'll just go away and never rear it's ugly head once the new lube is in it.

Paul