What Is Concidered A Good Highway Gear Ratio?

Yup like pushing a box into the wind. A cow is more aerodynamic

 

BTW post pics of your Duke swap.

 

will do, its a winter project, I'll be pushing the frame in the garage next week, engines in there waiting

 

Welcome from Michigan, 60cjer, Just my two cents, You have an OD, so there is a lot of Options for you. Like they are saying, I think 4:27's would work for you best. I have a 134 F Head in my 64 CJ 5. I put 66 V 6 axels in it, 3:73 gears, and used standard size 15" tires, 7.50 x 15". My Jeep tops out at 60 mph, but 50 -55 is best. It is good for touring the two lanes here in Michigan, and going Forest Viewing on the trails in the woods. Going fast in a CJ is not very safe as they are too short for high speed. I like the Iron Duke motor idea, I got lucky and found a NOS 134 F Head, Army surplus for my Jeep, so it is like stock, except for the larger brakes and 3:73 gears. Good Luck what ever you do, keep us posted, with pictures, please. Rick

 

Something which should be taken into account is not only the intended usage but where you live. Where I live there are very few long, steep uphill grades so lack of ability to hold 65mph up a steep hill isn't that much of a deal breaker.

 

4.27 with 25% O.D. unit provides a compounded FDR of 3.20.
Personally I think that's much too tall of FDR for any 4 banger.
I always figure 4.09 and 4.27 differential ratios to be compromise ratios.
A compromise is neither ideal for on road nor is it ideal for offroad, yet can handle both.
The compromise ratios are not intended for use with O.D. units.
Compromise ratios often work very well with D20 transfer cases.

Kaiser Motors Inc. specifically stated that Warn O.D. units were only intended for 4.88 and 5.38 differentials.
That statement was made in 9/1964 when the O.D. unit was initially approved as Jeep Special Equipment.
So the 4.27 ratio was standard at that time yet it was not factory approved to operate with the Warn units.

 

Yep!

 

Taking into account HP/LB, a stockish Duke would put you near 4 cyl TJ levels. Those came stock with 4.10s, and should have had higher numerical ratio IMO. I agree with Oldtime and Tarry, 5.38s with an OD will prolly be a solid combination. It just so happens that is likely the least expensive gearing option to obtain on an eCJ5.

If you think about it, it puts into a very proven track - 4CYL eCJ5 with 5.38s, except you have 33% more net HP than an FHead (~60HP to ~80HP).

 

I remember bringing my Jeep back home, first travel, with my son following in the Audi. Approx 450 miles of highway.
It was a torture; but people say hello.
Problems are : noise breakes weather speed is not the problem, because you cannot never go fast enough.
To drive an old Jeep on a highway is a philosophy. Each time it is a challenge.
These Jeep are good for roll-over, so we must be careful all the time.
Nice to have a good powerful engine to go up the hills but trucks go faster! Zen lessons are mandatory.