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Discussion Starter #1
I have a yj stretched to~ 110" with an isuzu turbo diesel in it. 4.10 dana 44-60 combo locked, th350 built, with np231 4 link front and rear. Mega short slip yoke with electric Vss . It's all done and driving very well. I get 18-20mpg on 42s around town even with the lockers. I go about 65mph. I'm just looking for more 4lo. I thought about a crawl box and an atlas. Or a doubler but my front DS is already long and my rear is already getting a little short. What's my best option without heavy modification . Doubler I think will add around 8" and crawl box about the same. How can I get a lower 4lo . Atlas TC are about the same length as stock np231 aren't they? I really don't want to re gear axles since without OD I only have max speed around 70-75 cause I'm limited to 3k rpms
 

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Whats your current rear driveshaft length?

Best option without an axle re-gear is change the tcase gearing.
 

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blatant asshole
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Yes a 4spd atlas is very very close to a 231.

A 231 4:1 from teraflex is $1200, then sye if you dont already, then its still a pot alum cast case.
 

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Snooty Poser
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It's not my money, but for what you are running, seems to me an upgraded transfer case is the best choice. Two Speed Atlas you can almost double the crawl ratio, the likelihood it will split into multiple pieces goes down. Yeah, $2900 so not an easy choice, but it will fit pretty well.
TWF Hero would be another choice, but more money yet, slightly lower gear available, (5.0 - 5.4)

You could go to a 3 or 4 speed transfer case and still be shorter than a crawl box, as I remember. Just add money.
 

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Discussion Starter #5
Yea atlas are expensive as all getup. I'll start saving my beans I guess.. It's already sye. I just can't stand to see the front shaft any longer.. The shop I had build mine already thought my front was getting too long without using a carrier. As I recall almost 5 foot.
 

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have you thought about running a wide ratio tranny? Not sure what adaptability options are for an Isuzu turbo diesel but you'd think if you can bolt up a TH350, you'd also be able to get a 465 in there too.
Wouldn't change your top end and you'd only be messing with the granny gear offroad. 1st/4-lo is almost like having a doubler. They are pretty short too at around 12" and bomb proof. You'd be shortening your front DS and lengthening the rear.

I'm calculating about a 73:1 final drive with a 465/231/4.10's/42's vs. 28:1 final drive with the current setup of TH350/231/4.10's/42's
with the 465, 2nd and 3rd would be pretty short on the street.

Is that a Jeep or Chevy 231 behind your TH350? you didn't mention an adapter but did mention a vss.
 

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Discussion Starter #7
It's an advanced adapter built 350 with their kit to my jeep 231 I put the 27 spline input in my case. Ya a465 would shorten buy I like the fact of being auto on the hills I climb around here. I was a manual Tranny when I had a sbc350 in it but couldn't stand needing three feet and no line locks. Went auto and now loving that. A 465 is an option to I guess.
 

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How about a SM465/420? That would over double your 1st gear ratios and it's probably shorter than the TH350.
 

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You could also do a 231/300 doubler which is almost the same length as the 231 in there now. Add 4:1 gears to the D300 and make it even lower!


You're at a 28:1 crawl ratio right now.

SM465 would bring it to 73:1
231/300 would be 74:1
231/300 with 4:1 gears would be 108:1
And while I'm at it...SM465 with 231/300 doubler would be 190:!
 
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