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Dana 20 capacity

addicted

Bronco Guru
Joined
Jun 7, 2009
Messages
1,936
Loc.
Broussard, Louisiana
I think the manual calls for 50w but alot of people use 75/90w just like in the axles. Im thinking its right around 3 pints. But you can just drain and fill until it starts dripping out of the fill hole.
 

DirtDonk

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Joined
Nov 3, 2003
Messages
47,355
My book says 2.75pts, but I just use the fill/check hole as my guide.
Correct on the 50wt, but it's specifically "non-detergent motor oil". Which, these days, is pretty much limited to a few brands of racing oil.
I can't remember if we've proven it beyond a doubt, but my assumption for that rating is two-fold. One is that some of the older rated gear lubes (like GL-1 through GL-4 maybe?) have additives that can attack bronze (as in bushings and shims) inside the t-case, so make sure the gear oil you choose is of a later rating.
If that's correct, then a GL-5 or higher should work fine. Might be GL-6 or higher though, so make sure by reading the label. Hopefully it'll still have that info there.

The second aspect is lubing the upper output bearings. They rely pretty much exclusively on the "splash-lube" method for their health. Using too thick of a gear lube might reduce how much gets up into the area in there because it's so sticky/thick. I'm sure some will still get in there from it traveling up the gears and walking along the shafts, but I figure why take the chance? So I use the thinnest gear lubes I can find. Which, in my case, was a 75w/90 synthetic. Super easy flowing, good cold-temp performance, the cushion of a gear lube (vs a motor oil) and easy to find. And because of all that, they're typically easier to pump into the case with one of the old Sta-Lube pumps I keep around.

And, even at the much higher prices of synthetics, it's relatively inexpensive because you're only changing them out every 25k to 40k miles in a daily-driver.
The exception to that last would be if you do a lot of wheeling in the water where you might want to change out your diff fluids fairly often. In that case, a synthetic may not be the best bang-for-the-buck.

Paul
 
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