• Registration trouble? Please use the "Contact Us" link at the bottom right corner of the page and your issue will be resolved.

Best approach to lowering gear ratio on a dana 44 (3.75) for wheeling.

D

Dana44

New Member
Joined
Aug 30, 2026
I just got a 1971 cj with the dauntless, t14 trans and dana 18 single stick. These all work great.
I can see already the high gearing on the axles, though great for pavement and forest service dirt will be a liability when running 4-low.

Useage will be under 100 mile secondary roads driving to access forest service dirt and moderate trails in my area. I would trailer the jeep if we go on adventures farther away. So I do not really need a highway geared cj.


My questions are:

1) IF I changed the axle gearing will they be that much weaker than the larger 3.75 ring sets? I read everywhere the ring gears are stronger but in the real world does it really matter? Would I somehow break the smaller ring set behind the mighty V6?

I have a Warn od on the shelf. So changing gearing may be the easiest and least expensive option. It offers me the best of both worlds within the limits of each as its not a crawler I am after. Just a good slow 4x4. (I used to drive logging skidders and I have all the nasty, technical wheeling a person could want already).

2) Teralow? Doing a search its hard to find the info regarding what I need to make this happen.

3) If I went with a Teralow, considering my present gearing, the OD is unnecessary, correct?
 
Dana44 said:
2) Teralow? Doing a search its hard to find the info regarding what I need to make this happen.
Click to expand...
Thinking about this myself. I'll be watching...
Dana44 said:
If I went with a Teralow, considering my present gearing, the OD is unnecessary, correct?
Click to expand...
Wouldn't be my choice. I'd want the OD for the ability to "split" the gears. I.E. 1st low is too low and 2nd is a tad high, so 1st OD could work perfect.
 
The factory optional 4.88 gear sets with the 225 and an OD make a really capable CJ both on and off road. Not as good as a truck 4 speed but way less work and no modifications required. And I like the TeraLows.
 
Does the Warn OD on the shelf match the T14? 10 spline. Tera lows would probably be the cheapest route. 3.15 tcase gears would take you to a 36.4 crawl ratio, instead of 28 you have now.
 
You should just try it as is first. My old '69 with V6 and 3.73 gears did just fine on normal offroading. If you're rock crawling you'll want lower gears, otherwise you're are probably fine as is.

Other observations:
  • Overdrives are nice. Not only do they allow you to run lower base gears and still go down the highway, they allow you more gear choices between the existing gears. This is really nice in hilly country and offroading. Having lots of shift levers is also fun. This is an overall 25% gearing change in the opposite direction you are looking for, but can let you run lower axle gears and still have decent highway gears.
  • Axle gearing. By the time you find gears for both axles, bearing/seal kits, a new carrier for the rear axle (might as well do a locker or limited slip while you're at it), and pay someone to do the setup (if you can't do it yourself), you'll likely be into it for $1000+. Whatever you gain in offroad gearing, you will lose in highway gearing. Adding an overdrive can help with that. Going from 3.73s to 4.88 is also about a 25% gear change in the direction you are looking for. Going to 5.38s is around a 44% change in the direction you are looking for, but is a big compromise for highway travel.
  • Tera-lo gears. This is about a 28% change in the direction you are looking for without effecting highway gears at all. This is a little over $1000, and a little more yet if you want to run them with an overdrive.
  • Truck 4 speed. This is the most effective single solution. With a 6:1+ granny gear, they double your lowest gear ratio without effecting your highway gears at all. This usually entails finding a transmission, buying an adapter kit, a rebuild kit, modifying the crossframe, modifying floorboards, and new driveshafts because the lengths change. This will probably cost $1500 minimum by the time you are done, but makes the biggest difference.
One fun thing is that you can combine all of these things to have a really high crawl ratio and still have nice highway gears. It's only money and effort.

A hypothetical setup with an SM-420, 4.88 gears, Tera-lo, and an overdrive, can have a highway gear of 3.66, crawl gear of 109:1, and have 16 forward speeds to choose from.

Some real life examples from the Jeeps I have owned:
  • 1968 CJ-5 with T90, 4.88s, overdrive: Number of forward ratios to choose from: 12, Highest gear ratio for highway travel: 3.66, Crawl ratio: 33.59
  • 1969 CJ-5 with T14, 3.73s (same setup as the original poster's Jeep): Number of forward ratios to choose from: 6, Highest gear ratio for highway travel: 3.73, Crawl ratio: 28.44
  • 1971 with T-18, OD, 3.73s (and a Buick V8): Number of forward ratios to choose from: 16, Highest gear ratio for highway travel: 2.8 (the Buick V8 can handle this happily), Crawl ratio: 57.99
  • 1963 DJ-3a (converted to 4wd) with SM-420, Tera-lo gears, 3.54s: Number of forward ratios to choose from: 8, Highest gear ratio for highway travel: 3.54, Crawl ratio: 78.73

Note how the truck 4 speed and Tera-lo gears in the DJ allow it to have a good highway cruise ratio without overdrive, but still have an almost 80:1 crawl ratio. It would be nice to have an overdrive on it to split gears sometimes though.

I made this online calculator you can play around with to your heart's content: https://fireball-v6.github.io/Code/
 
Fireball gave a very complete post as to options, so lots of things to think about.

In my 47, I have a V6, sm420 trans, stock Dana 18 and 5.38 gears. This setup works great when rock crawling, but as Fireball noted, highway driving suffers. At 55mph, the motor is hitting 3200 rpm’s. This works to get from Lake Tahoe to the Rubicon trailhead and to drive around Moab from trail to trail, but not for longer distances on a highway where speed limit is 70+ mph.

My 47 is primarily a trail rig, so this combo works. If it were more of a daily driver, I would reinstall the overdrive that’s sitting on the shelf. If you keep your gear ratio, an sm420 would help with trail manners…
 
Mine is chevy v6, currently t-90,(going to sm465), overdrive, 4.27 gears.

3.2 : 1 highway, which is fine here in Missouri on I70. I kick it out of overdrive when pulling the m416.

The sm465 won't just add the granny gear but the spread from 2nd to 3rd without overdrive with 4.27 gears will equal my original 5.38 gears with a t-90 and overdrive. As fireball mentioned the combination of gears and transmission yields granny gear, a stoplight friendly 2nd gear, and highway options. But again bigger engine that is very much alive on the highway with a 284/262 cam, decent compression, and a higher redline than a stock 4.3
 
James Orofino runs with me allot. We do everything including rock crawling. He has a 1970 cj5 V6, T14 3spd. Teralow in the dana18 and 4:88 gears front and rear and an OD.. He has a Eaton E locker in the rear and a I think a lok rite in the front. I have a 1971 cj5 with a V6 OD 4speed tranny dana18 Eaton E Locker in the front and a Power Lok in the rear. We feel we have a good all around cj5 that will handle just about everything we throw at them. Highway and off-road. Good luck. Just remember it's only money. Buy the best and only cry once.

Julius
 
Today I did some "farm wheeling". Even at idle and 4lo its too fast. If you got into any sort of obstacles you would be bashing around from maintaining rpm and progress, all the while clutching the beejesus out of it just surviving. Been there, done that.

Since I have an OD available am thinking 4.88 or 5.38 re-gearing.

The other alternative will be a Tera-low, which I have yet to talk with Herm about.54A0F2D2-B94A-4CF1-9423-10EEE638C126.jpeg
 
Last edited:
I am thinking that old Warn OD will be a six spline for a T-90 and if so it will not work with the T-14 in your Jeep, and the 10 spline planetary housing that fits the T-14 will be difficult to source. If you were to go with the Teralow gear set for the D18, that will require a different bowl gear as well.

It can be done, but it isn't cheap. My 48 trail Jeep has the 225 Dauntless, 5:38 axle gears, a T-14 transmission, Teralow gearing in the transfer case, and a 30% overdrive. It is capable of very low crawl ratio, and does well at hwy speed too. When crawling in 4WD the OD helps as a gear splitter, and when on road the OD allows it to easily cruise at hwy speed.
 
Last edited:
colojeepguy said:
Mine is just the opposite of yours. 4 speed with a PowerLok front and E locker rear!
Click to expand...
I’ve thought about a powerlock in the front since it’s a limited slip (better than my open diff), but I wasn’t sure this was a good solution. Seems you are happy with yours?
 
cj2atruck said:
I’ve thought about a powerlock in the front since it’s a limited slip (better than my open diff), but I wasn’t sure this was a good solution. Seems you are happy with yours?
Click to expand...
Certainly better than an open diff. But I'm planning on switching to a front selectable.
 
cj2atruck said:
I’ve thought about a powerlock in the front since it’s a limited slip (better than my open diff), but I wasn’t sure this was a good solution. Seems you are happy with yours?
Click to expand...

Powr-lok is great, I have one in my D25 with the "tight" spring configuration. I don't trust the 10 spline axles to last with a lunchbox locker. It has a slight preload but functions more like a torsen axle needing something on the loose side and multiplying it to the grippy side.

It definitely saved my hide when my rear axle went out and i had to limp home on I70 with just the front axle pulling. There was no way i could have held on with a front lunchbox locker but i had to pullnover into the ditch a bunch of times with fuel pump issues.
 
Last edited:
Jw60 said:
Powr-lok is great, I have one in my D25 with the "tight" spring configuration. I don't trust the 10 spline axles to last with a lunchbox locker. It has a slight preload but functions more like a torsen axle needing something on the loose side and multiplying it to the grippy side.

It definitely saved my hide when my rear axle went out and i had to limp home on I70 with just the front axle pulling. There was no way i could have held on with a front lunchbox locker but i had to pullnover into the ditch a bunch of times with fuel pump issues.
Click to expand...
D25/D27's are more than "fragile" even in the open configuration but you eliminate one of the two most explosive items (spider gears which are identical in both) with a traction device. You are still stuck with those milled 10 spline shafts with their built in stress risers. This one managed to remove most of the inner seal seat when it went and probably did me a big favor eliminating any thoughts of rebuilding that axle, or for that matter, any other D25/D27 axle. As far as traction devices, if you need 4x4 mode for snow/ice, forget any auto lockers in the front if your preference is to actually stay on the road.
52526545192_cfe4eed031_b.jpg


33940179710_2e3c179098_b.jpg
 
You must log in or register to reply here.
Back
Top Bottom