Quick Gear Oil question

[Gregg]

I'm going around checking fluids for tomorrows trip and I was a little low in the transfer case. I have been putting in Coastal 80W-90 but ran out. I was at Adv. Auto and couldn't find the correct weight in that brand so I got Valvoline 80W-90 (it does say "limited slip"). It shouldn't matter too much...right?

Thanks.

[Justin]

Yup you're fine. You could mix just about anything in there (except, maybe, vegetable oil) and be OK as long as you remained relatively close to the original spec weight. Lots of people actually run 50w oil in the t-case and this is what Ford suggested during the earlier years of the Bronco.

[Booger]

Yup you're fine. You could mix just about anything in there (except, maybe, vegetable oil) and be OK as long as you remained relatively close to the original spec weight. Lots of people actually run 50w oil in the t-case and this is what Ford suggested during the earlier years of the Bronco.

I remember many yrs ago talking to a mechanic who worked for High Country (back when they were Bronco cool) and he actually said the proper oil was a 50w gear oil. Not so sure if this was correct but I remember my 74 Bronco had a sticker on the door jamb saying the transfer case used SAE 50 gear oil. 50 weight motor oil has a viscosity roughly equivalent to 90w gear oil and 50 weight gear oil would have a viscosity somewhere around 0w something or other per this site http://www.teamrip.com/viscosity_chart.html.

[Justin]

I think Ford changed over to an 80-90 reccomendation sometime around 1974. I had thought it was closer to 1971, but could be wrong about that date. My understanding of the conventional wisdom it is that the 80-90w gives a little more protection and the 50w gives a little better mileage.

[Booger]

I think Ford changed over to an 80-90 reccomendation sometime around 1974. I had thought it was closer to 1971, but could be wrong about that date. My understanding of the conventional wisdom it is that the 80-90w gives a little more protection and the 50w gives a little better mileage.

I remember having the sticker on the door jamb on both my '74's. Gear oil has additives in it to help protect the gears whereas motor oil won't have it. Don't think friction modifier or even BG could make 50w work like 80-90.

[Justin]

I dunno. All the stuff I've read talks about SAE 50w non-detergent, which would limit you to just the racing oils. I've always just used gear oil and called it done, so I haven't looked into it much beyond what I've said above. I could definitely be wrong about that. The notion of using something that light made me nervous, especially since the Dana 20 wasn't really designed with 35" tires in mind.

[Viperwolf1]

It doesn't take much to lube the D20. I rebuilt one that was run with auto trans fluid in it and it was in good condition. Really clean inside too. I still don't recommend it though. Impossible to keep it from leaking.

[Shawns Fords]

It doesn't take much to lube the D20. I rebuilt one that was run with auto trans fluid in it and it was in good condition. Really clean inside too. I still don't recommend it though. Impossible to keep it from leaking.

makes them really noisey too. I had a different Case in my 78 and guy put ATF in it and it drove me nuts for years. I finally went back to gear oil and she quieted down really nicely and started shifting smoother as well. A lot of guys decided to put ATF in them old cases but I do not like doing that.