NP231 Transfer case lower gears

[troublemakerbuggy66]

I don't know if anyone is even making 4:1 gears for 231's anymore.

Basically your options are:

1. Try to find a used 4:1 set

2. 231/231 doubler(or some kind of junkyard doubler combination)(probably too long for your setup)

3. d300 flip kit and 4:1 kit(if anyone still makes them, or try and buy used)

4. buy a rocktrack np241 out of a rubicon(there's one on here for sale right now) I personally think they are overpriced. But given that there aren't many purchasable options, that might be the way to go.

5. Atlas.

I have one of the early terralows. Needle bearings instead of the bushings. Teraflex wanted to buy it back from me. 95 YJ 2.5 on 40's and rpm doesn't matter, still running it after 11 years. Best bet an atlas and you can adapt to different transmissions and outs.

 

[CarolinaCrawler1]

basically all of those options are a reduction housing that holds a NP231/241 planetary (the Ecobox is a DIY kit where you use a donor case). IMO it's a much cleaner and higher value setup than the cut-case NP doublers that used to be common.

The advantage of using a D300 (or even a NP205) behind a reduction housing/crawl box is that the overall size is about the same as a stock NP231/241 (because of the the case configuration of a parallel gear driven case vs a chain drive case).

it works out better in Jeeps which tend to have long front driveshafts and short rear shafts.


I know a NP205 is super-overkill for a 4cyl Jeep (and heavy) especially one that sounds to be stock-ish. But a Ecobox+Ford 205 is the cheapest, strongest, shortest setup you'll be able to to put together for a driver-drop 4 speed tcase.

No doubt the eco-i to 205 is the strongest set up out there (even stronger than an atlas). I don't much care for flipping a dana 300 just because its damn near impossible to keep it from leaking. One transfer case I think get overlooked is a bronco dana 20. I think for a 4 cyl rig, they would be plenty tough and most importantly short. Plus there are available upgraded outputs.

 

[Wagfabulous]

Id take the money it took to buy a 4:1 kit and put it back in my pocket and buy a jeep with a 4.0 and an auto man . I wheeled this exact setup for years in a yj I had . My friends had similar jeeps with the 4.0 and they had nowhere near the trouble I had "easing around tight spots" . To get enough tire speed to bump over something in 4L with 4:88s and a Detroit in the back , 2nd gear clutch drops were required. Not to mention even with the 4.88s and 34 ltbs 5th gear was still useless on the hwy unless it was completely flat . I cant imagine trying to pull 36s . Just my two cents.

 

[Weezul]

Per the post above. I've got a 98 TJ with the 4.0, 3 speed auto, 231 and 4.56 gears on 38s. It tries to power through the brakes in 4 low. I had to move a friends JK Rubicon on the trail and figured the 4:1 would be awesome. I let off the brakes and it didn't even move. Maybe it was the JK electronics messing up the crawl ratio. I let him drive mine up the same line and he was shocked how easy it was in mine.