What grade oil for D20?

[68stang73]

What are you guys using? I seem to be getting mixed reviews.

 

[bronconut73]

non-detergent 50 weight engine oil is what Ford called for in the Dana 20.

But oil technology has really improved in the last 40 years. I am using Red Line gear oil 75/90.
Gear oil and engine oil determine their weight/viscosity differently, in that, the 75/90 Gear oil is similar weight/viscosity as 50 weight engine oil.

 

[68stang73]

Thx for the info. I think my store has that too.

 

[blubuckaroo]

Why not just use the Ford recommended SAE 50 motor oil? You can get it at most good auto part stores. Valvoline SAE 50 Racing oil. That's all I've ever used. Over 280K miles without issue.

 

[68stang73]

LOL! over here they all said "I've never heard of 50w oil" So here we go right.

 

[Harley]

Royal purple 75-90 in the 3spd and D20

 

[Broncobowsher]

Why not just use the Ford recommended SAE 50 motor oil? You can get it at most good auto part stores. Valvoline SAE 50 Racing oil. That's all I've ever used. Over 280K miles without issue.

Because the only 50wt motor oil you will find today is detergent motor oil.

In reality the dana 20 will survive a long and happy life with just about any oil. Just using normal gear oil keeps the oil inventory down. There are probably more transfer cases filled with gear oil from old service centers doing service jobs and filling with standard gear oil back in the day then you think there are. Every other dana 20 application is gear oil. Ford had some strange thing about filling manual transmissions with motor oil a long time ago.

 

[boomeroid]

is there any advantage to using synthetic gear oil in transmissions and transfer cases?

 

[bronconut73]

is there any advantage to using synthetic gear oil in transmissions and transfer cases?

Yup......

 

[lonesouth]

I just run the same stuff as in my diffs. 80w120 or something

 

[Justafordguy]

75w90 lucas synthetic is what I use in the transfer case and the diffs.

 

[Rustytruck]

I use Amsoil synthetic gear lube 75 - 90 it has the same viscosity as 50 weight motor oil. I compared the 2 with lab equipment at work when I was chasing J shift shifting difficulties. The synthetic works better especially when cold. Been running the Amsoil in the transfer case for almost 30 years now. I got into it when they use to have the little gear gismo as a sales tool at the parts counter when they had real auto parts stores.

 

[Bronco Junkie]

75w90 lucas synthetic is what i use in the transfer case and the diffs.

x2......

 

[blubuckaroo]

Because the only 50wt motor oil you will find today is detergent motor oil.

In reality the dana 20 will survive a long and happy life with just about any oil. Just using normal gear oil keeps the oil inventory down. There are probably more transfer cases filled with gear oil from old service centers doing service jobs and filling with standard gear oil back in the day then you think there are. Every other dana 20 application is gear oil. Ford had some strange thing about filling manual transmissions with motor oil a long time ago.

Yea, I had the transmission worked on in a shop once and they had to pull the transf case. After that, I noticed shifting in and out of 4H was much more difficult when cold. I checked, and sure enough, they had filled it with gear lube. I had to show them the sticker on the door which showed the SAE 50/30 specification. When I asked the guy "why did you do that?" he said he had no SAE 50. Good thing he wasn't doing a tune-up. He probably would have used the wrong spark plugs because he didn't have the right ones.%)

You can't just use your gut feeling about what should go in a gear box. Chevy S-10 pickups took SAE 30 in their trannys and would shift terrible when gear oil was put in by mistake.

I can't find "non-detergent" in the Ford specs. I understand that detergent is there to keep engine contaminants in suspension, but the only contaminants that should occur in a transf case are metal particles and water. No detergent would keep either of those in suspension.

I'm no oil engineer. Way above my pay grade, so I feel more comfortable using the expert's recommendation.

 

[SoCal68Bronco]

75w90 Valvoline synthetic

 

[cldonley]

I like the Amsoil stuff, but the bottom line is it has to have oil.

 

[Viperwolf1]

Keep in mind that GL-5 gear oils are not very nice to the brass thrust washers on the ends of the cluster shaft in a D20. GL-4 is fine if you can find it. Synchromesh compatible trans oil is fine too. That may be the reason Ford specified SAE 50. If you plan to rebuild your D20 every decade or so you can use whatever you want.

 

[lonesouth]

Viper, can you post up an article indicating that is still the case? I've read so many conflicting reports that GL5 is safe/not for brass.

Ultimately, I know for certain that GL4 is safe, but curious about the ongoing debate on GL5.

 

[Viperwolf1]

Viper, can you post up an article indicating that is still the case? I've read so many conflicting reports that GL5 is safe/not for brass.

Ultimately, I know for certain that GL4 is safe, but curious about the ongoing debate on GL5.

The very reason that synchromesh trans fluid exists today indicates that GL-5 is probably not safe. Lots of articles out there.

 

[boomeroid]

I use Amsoil synthetic gear lube 75 - 90 it has the same viscosity as 50 weight motor oil. I compared the 2 with lab equipment at work when I was chasing J shift shifting difficulties. The synthetic works better especially when cold. Been running the Amsoil in the transfer case for almost 30 years now. I got into it when they use to have the little gear gismo as a sales tool at the parts counter when they had real auto parts stores.

Thanks, that makes sense.