1966 F250 Rearend question

[lucky23]

My '66 F250 has the stock Dana rear end with the 4.10 gears. I really want to change it out for the 3.54. Now, I understand that ratio is really difficult to find, so my question is: what is a more feasible alternative? I heard changing gears in a Dana is difficult, so would finding a complete rear end be a better option? What rear ends would work easily for my 250?

[bruceandersson]

You are going to have trouble finding a much lower ratio for a 3/4 ton rear end. The newer trucks with OD have 3.73 or so. Some of the farm duty trucks came with 5+ rear ends. Have you considered finding an overdrive transmission? This would retain the ability to pull as well as address the final ratio issues. I have done this in my '65, using a transmission from a mid-70s f150.

[Dirt Devil]

My 64 F-100 had that rear end - it was very unusual, but it came as an option - back in the day when these trucks really had to work hard. I was never able to find a higher gear for it. I put up with it for 10 years, finally got a 9 inch Ford punkin' rear end. I sold that Dana 60 to some race car builders for $400. I was quite pleased.

[chris401]

I have heard of a hd axle with 3.08 gears behind the 6.9. I haven't seen any 10 3/4 Ford that high, 3.55 is the highest gear I've seen. Anyone else?

[frank66]

Where are you at? I've got a Dana 60 with 3.73's that I can give you. I just picked up a 9" for my truck. It won't be that big of a change, but its free. I'm on Long Island.

[lucky23]

Damn! I live in Portland Oregon.

[6166 Junkyard Dog]

all of the 3/4 ton rear ends will interchange from 1955 to 1972 and a lot of the 68/72 trucks had the 3:54 gear ratio as long as using the whole assembly that's from brake drum to brake drum

[chris401]

I have heard of a hd axle with 3.08 gears behind the 6.9. I haven't seen any 10 3/4 Ford that high, 3.55 is the highest gear I've seen. Anyone else?

I did some research and found that a Dana 61 is designed for gears as high as 3.08.

[Blackwaterforge]

Isn't a 61 a semi-floating axle?

[chris401]

Don't know.

[Indy63]

Should just be a plain ol' Dana 60, but it wouldn't hurt to get a positive ID before ordering parts as you never know what's happened over the course of the last 47 years. 3.54 is easy to get just about anywhere from fleabay to vendors like Randy's Ring and Pinion.

edit: DO NOT BUY DANA 61 GEARS FOR A DANA 60! It is a different axle with more pinion offset.

[lucky23]

I have a chance to buy a rear end out of a '70 F250 w/ 3.73 gears for $150. But, I think I. Gonna try and hold out for a 3.54. I don't think the difference between 4.10 and 3.73 is enough to justify the work....

[lucky23]

You are going to have trouble finding a much lower ratio for a 3/4 ton rear end. The newer trucks with OD have 3.73 or so. Some of the farm duty trucks came with 5+ rear ends. Have you considered finding an overdrive transmission? This would retain the ability to pull as well as address the final ratio issues. I have done this in my '65, using a transmission from a mid-70s f150.

Hmmm, I never thought of that.

[Poppyred66]

The 3.54 is not particularly rare but is hard to find. The best source is a 460 automatic camper special. I couldn't find one so I settled for a 3.73, which was a great improvement over the original 4.56.
Eric

[lucky23]

Actually, I found a 1966 Dana axle w/ 3.54 gears on craigslist. $100 for the complete axle with hubs. (:

[chris401]

Actually, I found a 1966 Dana axle w/ 3.54 gears on craigslist. $100 for the complete axle with hubs. (:

Where is it and are you going to get it?

[lucky23]

Yeah, I picked it up yesterday! I had to drive out to estacada to get it... The guy pulled them out of his '66 F250 so it should be a direct swap. He put a 3.73 in his to pull his boat. Really nice guy. Man, those suckers are HEAVY.

[BKW]

My 64 F-100 had that rear end - it was very unusual, but it came as an option - back in the day when these trucks really had to work hard.

No F100 came with a Dana 60 as it was only installed in F250's.

1963/65, some 1966 F100's were available with the Dana 60.2 w/Limited Slip. Dana 60.2 is not a Dana 60!

1966 was the first year that Dana 60's were available with 3.54 & 3.73 ratios.