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

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...
Agree on the 10 spline front axles with an e-locker, I doubt the axles would last long. I carry spare axles front and rear, but have no interest in changing an axle on the trail. Same reason I switching the rear 10 spline to full floating before the Rubicon trip next year.

I had open diff up front on the Rubicon trip and only winched twice, so the open diff didn’t really hinder performance much. I think the articulation with the coils and long arms may have helped keep all the tires on the ground.
 
On the recent Colorado trip, I was the only one who had a limited slip front diff, everyone else had a front locker. I had real trouble on the Grizzly Lake gatekeeper. As we all know, it couldn't be my driving :D so I'm blaming the front Power Lok.
I have most of the pieces to put together a D30 with E locker, hopefully that'll happen this winter.
See post #20
 
Another option would be a AX-15 5speed they have a 3.83 first gear and a .79 OD in 5th. You can even get one adapted to use a Warn type OD which will allow you to split all them gears and a have a a rig that with 30" tires will be turning 1485 rpm at 60mph in 5th and OD

at the same time the 3.83 first with a D-18 transfer case low range of 2.42 the same 3.73 rear gears and 30" tires you are turning 1960 rpm at 5 mph with a crawl ratio of 34.7

You would have 20 forward and 4 reverse to chose from. Might need a cheet sheet on the dash LOL.
 
Saginaw steering, flanged rear axle? Open front knuckles? Swing by smoor any given weekend and give low range a try.
 
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Lots of good suggestions.
My goal is 55mph at reasonable rpm and as slow as I can get 1st lo4x4. I do not care about wandering much outside those parameters. I realize without both a terra-lo and lower axle ratios AND the OD I am not going to reach my holy grail. But maybe... by re- gearing, OR a t-lo, I can get almost there. Cannot have both because both are going to be more than I want to spend. I have to choose one or the other.

Better view of the axle tag.
C3534033-5C8B-4167-89F0-F67BE3C760A8.jpeg
 
Dana44 said:
Lots of good suggestions.
My goal is 55mph at reasonable rpm and as slow as I can get 1st lo4x4. I do not care about wandering much outside those parameters. I realize without both a terra-lo and lower axle ratios AND the OD I am not going to reach my holy grail. But maybe... by re- gearing, OR a t-lo, I can get almost there. Cannot have both because both are going to be more than I want to spend. I have to choose one or the other.

Better view of the axle tag.
View attachment 107997
Click to expand...

You need a sm420 skip the other options and get a 4 speed. See you at Moore expo?
 
The only thing stopping me from the Muncie 420 is it is made to sound like a lot of work.

Not knowing its granny gear, what creep ratio will it give me in front of the 3.75 axles?

Edit: I found this to answer my question.
FBCDEBF6-6CB5-404A-A713-BCB4AAB3B90B.jpeg
 
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It'll drop 1st high range from 11.56:1 to a 2nd gear at 13.35:1

Mine is currently 11.95:1 in 1st high. Don't get worked up about crawl ratios we don't have slick rock around here you drive with momentum.
 
Then its the suspension dictating things. A body can only stand so much bashing. We see enough rock and ledges here to really feel how the stock ratios in an older jeep with its stock springs pounds the heck out of you. I take the point you make about momentum and use that too. But there are moves when slower, and slower still, is just easier.
Keep the thoughts coming. Learning a lot about how to set up my jeep.
 
Dana44 said:
The only thing stopping me from the Muncie 420 is it is made to sound like a lot of work.

Not knowing its granny gear, what creep ratio will it give me in front of the 3.75 axles?

Edit: I found this to answer my question.
View attachment 108001
Click to expand...

As I noted above, you can use my online calculator to enter tire size, axle ratio, transmission/gear, Low range type, and overdrive to calculate your overall gearing and the engine rpm and any speed in the selected gear:

Vintage Jeep Speed and Gearing Calculator

You can try out about any scenario you can imagine.

And... even though a truck 4-speed is a decent amount of work, it has the largest crawl gear change of any single modification and doesn't effect your highway gearing. An Sm-420 and will give you a 65:1 crawl gear with no other changes to the Jeep. That's into rock-crawling territory. As usual, the best solution is never the easiest.

If you're really bored and want to see what a 4 speed install looks like, you can start reading the build thread for when I installed a T-18 and Overdrive in my '71 around this post: https://www.earlycj5.com/index.php?threads/145880/post-1652906

If you're still bored after that, you can read about installing Tera-lo gears in my DJ-3A starting at this post (It already had an SM-420 in it when I got, but I did shove it 2 inches up into the floorboards for more ground clearance): https://www.earlycj5.com/index.php?threads/160864/post-1868601
 
If you're interested in a 4 speed swap, Tim's transmission thread has good info about the common conversion candidates. Each one has pros and cons.
timgr

Thread 'Truck 4-speed Transmissions As I Understand Them'

Been working on this for a few days -

The forum gets a lot of questions about what transmission to use when upgrading from the original 3-speeds that came with these Jeeps. We will limit ourselves here (mostly) to the "early" Cj-5s and CJ-6s, which were built by Willys or Kaiser from 1955 through 1971. Also, this info generally applies to the M38A1 and M170 military models, which are essentially the military models that became the CJ-5 and CJ-6 respectively. We will touch briefly on the intermediate ('72-75) and late ('76-86) CJs after completing the discussion of the earlys and the...
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And here's my T18 swap in my 70 cj5.
colojeepguy

Thread 'T90 To T18 Swap'

For those who haven't been following the Colorado epic thread, I'm having clutch and/or trans issues with my CJ. This is a 70 with a stock 225 and cable operated clutch setup, with a T90J & D18 with a Warn overdrive.
Basically, I can start the engine, depress the clutch, and I can shift into any gear without a problem. So, I put it in 1st, drive away, and when I try to shift most of the time I can't get it out of 1st gear! When I can shift out of 1st, it won't shift into 2nd. There's no grinding or anything, it's just like 2nd isn't there. Same with 3rd. I don't think this is a clutch...
 
Transmission swap should increase overall value.
Regearing two axles won't change overall value.

With a transmission swap he can use the 6 spline overdrive or low gears.

My inlaws have the 66 with buick v6 3 speed and 3.73's and it is great on the blacktop but I get what he's talking about. Still I really feel like starting with the transmission will get him the 6 spline output for the overdrive or future teralows.


Missouri Ledges... this is at Rush Springs Ranch.


Here is a hill climb in that park, again 3 speed with 5.38s

Now this is my in-laws with buick 225, 3 speed, and 3.73 gears.
 
Dana44 said:
What do you all think of putting in a T18 with the granny gear?
Click to expand...

I love the T-18 I put in my '71. If you do a T-18, find a later one with reverse to right and back. They shift better. Mine shifts as easily as the T-14 that was in the Jeep before. The Sm-420 in my flatfender has a lower granny gear, but shifts slow and clunky like a 1950s dump truck.
 
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