Topic: Gear Ratio/t-case opinions

[stan98tj]

Ok, still planning on doing the VW 1.9 Diesel swap, but I'd like to bounce a few ideas off you folks.
I am running 4.56 gears on 33s with a 3spd auto. HPA has informed me that I MAY have to upsize to 35s in order to bring the RPMs down to where they want them to be. Fair enough, my axles are built up and can handle it.

Here's my question: Once I do the swap, I will have the trany built up at a local guy's shop with beefier components and what not. That leaves the t-case. Because I have an auto, I believe I can actually run a Rubicon case. What I want to know is whether the 4:1 ratio in 4low paired with my 4.56 gears will be "too low." I've been bouncing this around to other folks and some believe I will constantly be dropping in and out of 4low as I move from obstacle to obstacle.

I like the 4low ratio I have now, but I would like to have the 4:1 option. Without doing an Atlas or Klune is it possible to even keep the 4hi/4low ratio we have now and then be able to drop into an "extra" gear geared at 4:1? Would that be a "crawl box." Im a bit uninformed on the whole subject and would hope you guys could clarify.
Thanks!

[sharpxmen]

not sure if i'm right or wrong but i believe with an auto you don't really need 4:1

[aw12345]

Use this, input your info and see what you want for crawl ratio

http://www.grimmjeeper.com/gears.html

[aw12345]

Seems to it will be a nice combo as long as your trans has the correct spline count for the transfercase and you might have to get a sleeve or different seal from terra so it won't leak. Friend of mine had a 241 installed behind his 3 speed auto and loves it, but it kept leaking oil after pulling the case 3 times the shop caller terra and got a sleave or seal from them and it solved the leaking

[neale_rs]

A friend of mine had a 4.0 TJ with auto, normal np231, 4.88 gears and 35's and it worked really well in the rocks.  I think the 4.0 might be too low unless you use it only in rocks.  Maybe the 4.56 gears would make it better but not sure.

[stan98tj]

Seems to it will be a nice combo as long as your trans has the correct spline count for the transfercase and you might have to get a sleeve or different seal from terra so it won't leak. Friend of mine had a 241 installed behind his 3 speed auto and loves it, but it kept leaking oil after pulling the case 3 times the shop caller terra and got a sleave or seal from them and it solved the leaking

So I used the calculator and basically what I got from it is that it will be a bunch slower when In 4low. I figured as much. I don't know enough about the numbers to be able to effectively determine if those ratios will be too low, if I will be forced to drop out of 4low to 4hi to move from obstacle to obstacle on the trail (currently I basically stay in 4low the whole way whether in the rocks or on a muddy track to the next series of rocks). Also want to know if I am trying to climb a slippery surface of rock and need a little wheel speed if those numbers I calculated are too low.

[stan98tj]

A friend of mine had a 4.0 TJ with auto, normal np231, 4.88 gears and 35's and it worked really well in the rocks.  I think the 4.0 might be too low unless you use it only in rocks.  Maybe the 4.56 gears would make it better but not sure.

Im swapping to a diesel 1.9l

[Jeffy]

The torque converter will give you about 1.5-2x multiplication of torque when RPM's kept low.  Most of the auto's I've seen with Atlas's run 3.6 or 3.8:1

[stan98tj]

Ok, now I want to eliminate or expand on the 2nd question I had:
Would it be possible to keep the stock ratios I have in 4hi and 4low and then have a crawl box rated at 4:1? I may be misunderstanding how a crawl box works. Essentially what I'm asking is keep my stock stuff and then have a lever engage and get 4:1 or as close to that as possible. I feel that would give me all the options I would ever need.

[Jeffy]

A crawler box aka: doubler is usually a secondary gear box.  A Klune V, Mad Rooster, Rubi-Crawler, etc...

The only real consideration/limitation is driveline length.

[stan98tj]

A crawler box aka: doubler is usually a secondary gear box.  A Klune V, Mad Rooster, Rubi-Crawler, etc...

The only real consideration/limitation is driveline length.

So this would be a twin stick setup. Should I even be considering this or is this far more than what I need? I wouldn't mind a 4:1 "add on" to have if I ever need it.

[neale_rs]

Im swapping to a diesel 1.9l

I know, but both are motors with more torque than the 2.5.

[sharpxmen]

Ok, now I want to eliminate or expand on the 2nd question I had:
Would it be possible to keep the stock ratios I have in 4hi and 4low and then have a crawl box rated at 4:1? I may be misunderstanding how a crawl box works. Essentially what I'm asking is keep my stock stuff and then have a lever engage and get 4:1 or as close to that as possible. I feel that would give me all the options I would ever need.

i think it's pointless with an auto to be honest (to install a doubler/crawl box).

[aw12345]

4 speed Atlas baby, willl do it all move the engine forward so you get more driveshaft length
Truth be told V8 auto Jeeps do well with 3.4 to 4.3 to 1 transfercases even in low range you can make enough wheel speed, trans will still shift to second or third

[stan98tj]

4 speed Atlas baby, willl do it all move the engine forward so you get more driveshaft length
Truth be told V8 auto Jeeps do well with 3.4 to 4.3 to 1 transfercases even in low range you can make enough wheel speed, trans will still shift to second or third

I feel like the atlas or Klune is way more than I need. I got a buddy with a klune, something like 9.8:1 ratio. Very cool, but I don't think I need anything to be doing any front digs with.