Best Gears

Hey guys I have a 56 cj6. Currently have a Chevy 327, t-15, Dana 20 transfer case, 31 in tires. I have 2 sets of axles and am debating which once I want to put in. One set has 3.73 gears and the other has 4.27. What do you think is best. It's going to be 60% street , 40% dirt use.... nothing serious and no rock crawling. Please let me know. Thanks!

 

For cruising with a V8 and 31's with no OD, I vote 3.73's. 4.27's will put you close to 3k rpm cruising on the freeway.

 

on the money

 

If it were mine, I would go with the 4.27 gears. Tell us more about the axles. A set of open Dana 30 / flanged Dana 44 axles with 4.27 gears is a desirable pair of axles.

How fast do you want to drive? 3000 RPM will be somewhat noisier than 2500, but it should not make much difference to the engine. Insulate the floor, use a quiet fan, use a quiet exhaust, use quiet tires ... no problem.

 

Swap one rear in and drive it around; don't like it, try the other.
When satisfied, then install the front axle.
Costs you nothing but time.

 

Dana 20 overdrives are extremely scarce and little more than a novelty item.
So I think 3.73 ratio is right near the goal for a daily driver on hiway seeking optimum fuel mileage.
If used mostly for local commutes and or solely to get to the trail head then 4.27 is a better bet.

Do as Jim suggest above then report back here to us with your experienced opinion.

You might also consider adding Tera 3.15 gears to the Dana 20.

 

3.73 unless you change to 75% off road duty.

 

I'm running 3.73's in my 75 and kind of like them. If I were doing a lot of off road driving. the 4.27's would be better.

 

Thanks for the replies guys. I think I will put in the 3.73 then. Majority of my driving will be around town with the occasional off-road. Definitely need to be able to cruise at highway speeds because I'm driving my JEEP to the trails. if it feels way to high then there's always the option of swapping but I'm trying to avoid that

 

Interesting how split this is....

 

I have 3:73's in my 64 Tuxedo Park, with a 134 F head, T-90 , T18, and 750 X 15" tires. I use it for Forest viewing on trails, and cruising to town for parades and shows. It will sustain 50 mph without straining on the roads and cruise the trails at low speeds well too. The club where our cabin is has 11,000 acres of hunting land, and 2,000 acres of cabin land, the max speed is 20 mph anywhere on the property, so it is in second gear a lot.

 

Is there such a thing? I have never seen one.

 

You'll miss those 4.27s off road.
Oh yea, I have 5.38s and drive to most trails.

 

Yeah its a really tough call....
On road 3.73 is way better but on trail 4.27 is way better.

 

that's it pretty much what it comes down to... and if your being honest with yourself about the road/trail split the answer is fairly clear..

 

Mmmm. With t-15 I'd go 4:27. 327's Dont mind reving some. If you had a t-18 I'd go 3:73.

 

This.
I'd go 3.73s and keep an eye out for a 4-spd.

 

You make a good point. Dana 20's have a horrible low range gear. My dad's Flatty has a Chev 283, T-98 4 spd, Dana 18 and 3.73's. It cruises down the highway much better than my 4.27 geared flatty did, but it works great off road too because of the granny 4 spd and lower ratio of the Dana 18. Alternatively My sisters 75 CJ-5 runs a 304, 4:1 T-18 and D20 with 3.73 gearing. Also cruises great down the freeway and is OK off road, but occasionally I wish it had a lower first gear or lower low range or both. Either way, it's relatively easy to make up for lack of off road gearing with Low range T-case gearing like the 3.15 or a granny 4 spd and have the best of both worlds.

 

I think the point about the 327 not minding the extra revs is the key here. My brother had a 327 in an old '72 Chevy pickup and that thing wasn't great for grunt down low but loved the higher revs. I'd do the 4.27 gears and if it was a 305 or 350, I'd do the 3.73's.