Gears or Over Drive

My thoughts are this.

If you put in the 4:27 gears and drive it ALL of your drive train turns slower speeds.

If you keep the 5:38's and use the overdrive (which effectively makes the gearing 4:09 as seen by the engine and transmission) the only things turning slower are the engine and transmission.


Something to consider.

Plus I am not sure you really want to be pushing one of these old girls up to 65.

I have decided to stay off the free-ways and run the secondary (or what ever you call them) roads and enjoy the scenery the lower speeds allow me to see.

If I could find them, I would seriouslly consider 4:09's or 4:10's for my '60. Or even the 4:27's.

 

Overdrive!

 

Is driving 55 such a highway risk?

I drive half of my distance to work on the interstate, and I don't feel any pressure to drive 65 or 70. In the right hand lane, 55 is fine, and I'm in the middle lane at 60. I can drive faster if I move over to the left, but I have never felt that slower speeds were unsafe if I keep right.

 

Around here 55 is a danger once outside of the city, speed limits are 70mph so a lot of people are running near 80mph. In the city it is acceptable but you will be getting passed left and well left since the speed limit is either 55 or 60mph. And with those speed limits a lot of people are still running 65-75mph in the city.

 

Around here 60-65 is about the minimum speed that you can go on the freeway without getting a bunch of angry jerks tailgating you.
I have 4.88's, an OD and 31" tires-I consider this to be a good all around combo for off-roading while still keeping some highway capability.

 

No brainer for me. The OD is a LOT less work to put in than new gears. I also like having a 6 speed instead of a 3 speed.

 

The engine only has about 1,000 miles on it and I have all the 24 volt waterproof system for it.

Thanks I am already indecisive enough the reason for the choices primarily were I have them already.

Generally I set my front ends up with -3 degrees of caster, with a Saginaw box and 11 inch brakes I feel it will be safe at the 60-65 mph range. Around here they are all 2 lane hi-ways if it was 4 lane no biggy I would cruise in the right lane. I also have a lot of logging trucks around here and a few are more suggestive that you speed up or get out of there way. ( No insult intended ). And its usually 10 plus miles to a safe spot to turn out.

 

Something else to consider-do you have the ability to set up the gears yourself? Most people dont have the tools or knowledge to do this, but most competent weekend mechanics could install an overdrive. If you have to pay someone to set up the gears it'll add quite a bit to the $$$ involved...

 

Sorry typo - I set them with the upper king pin behind lower king pin in direrction of travel ( to clarify)

Something else to consider-do you have the ability to set up the gears yourself? Most people dont have the tools or knowledge to do this, but most competent weekend mechanics could install an overdrive. If you have to pay someone to set up the gears it'll add quite a bit to the $$$ involved...

I can set them up properly But it takes me all day, I also have a Great gear guy that does them very reasonably for me- If work is booming he does them, if work is slow I do them I either have time or money never both.
By the way colojeepguy Awsome bumper sticker.

 

Jeep Universal Gearing Perspective
4.88 final drive ratio was used for the early LRV military models.
In 1945 the "Universal" concept was developed to market post war Jeeps.
5.38 final drive ratio is the standard for the CJ-2A Universal and many later CJ's.
All post 1953 CJ's benefitted from the 1950 Hurricane "F-head" developement.
134 Hurricane horsepower was increased by 20% over that of the 134 Go Devil.
By the early 1960's HP and speed heavily influence the whole automotive industry.
So in 1963 Kaiser Motors Inc. decided to increase the CJ's speed potential via final drive gearing.
The previous 20% HP increase had made this change feasable.
The previous standard final drive ratio was increased from 5.38 to 4.27.
After Novemver of 1962 all Hurricane powered CJ's come standard with the 4.27 final drive ratio.
5.38 final drive ratio became the post 11/1962 option for all Hurricane powered CJ's.
In September of 1964 the infamous Warn overdrive was designated as "JEEP APPROVED SPECIAL EQUIPMENT".
The WARN O.D. was only approved for Jeeps having 5.38 and 4.88 final drive ratios.
It was never designated nor intended for use with higher final drive ratios.
The WARN O.D. with 5.38 final drive effectively yeilds a 4.03 final drive ratio.
The WARN O.D. with 4.88 final drive effectively yeilds a 3.66 final drive ratio.
In 1965 the 3.73 final drive ratio became standard for Dauntless powered CJ's.
4.88 Front with 4.89 Rear final drive ratio became available as an option for these Dauntless CJ's.

A 5.38 geared Hurricane powered CJ in good condition will readily benefit from Warn O.D.
unless the hills are long and fast (over 55 mph) or approaching steep grade with transmission engaged in 3rd gear /O.D..
A 4.88 geared Hurricane powered CJ in good condition will readily benefit from Warn O.D.
unless the hills are anything but a slight incline with transmission engaged in 3rd gear /O.D.
4.27 final drive with .75 O.D. is geared to fast to be usefull for CJ's inherent stability yeilding 3.20 final drive ratio.

I personally have driven various Universal models for hundreds of thousands of miles.
The standard (non modified) early universals do not handle well at speeds over 65 MPH.
If operating at "compromise sustained engine crankshaft velocity" of 2700 RPM
the 5.38 /Warn O.D. equipped CJ with 6.50 x 16" (29.5') tires will cruise at 57 mph,
the 4.88 /Warn O.D. equipped CJ with 6.50 x 16" (29.5) tires will cruise at 63 mph.
Obviously the 4.88 ratio yeilds about 10% speed increase over the 5.38 ratio for both crawling and highway cruising.

In 1972 AMC went to the 3.73 final drive ratio as standard on all CJ's.
Then 4.27 final drive ratio became the option.
With the post 1971 D-20 transfer case used in CJ's a Warn O.D. is no longer compatable.
This is where the 4.27 final drive ratio has its true merits.