NP231 doubler without axle gears

K

kinlawk

NAXJA Forum User
Location
north carolina
I am at the point in my build that i need lower gears. The thing is that I don't want to dump money into the stock axles when I plan on upgrading to 60's in a year or two. Right now I have 3 NP231's sitting in my garage, one with S.Y.E.

So I need some input, would it be stupid in your opinion to double the transfercase before putting gears in the axles? I found a kit to double the transfer case for $499.00 and I figure that it will cost about $350 per axle to gear.

Rig Specs: 95 XJ, 4.0 auto, NP231 S.Y.E., 5" lift in front 6" in rear, and 33" X-Terrains.

Thanks for any input in advanced.

SANY0310.jpg
 
If you daily drive it, it's still going to suck on the road. Also, you'll be putting the driveshafts and pinion gears under more torque than before. It will do a hell of a lot more for your crawl ratio though, for example let's assume you have an auto and 3.55 gears and use a stock np231 as your doubler box (2.72:1 gear ratio), you'd have to regear to 9.66:1 in the axles (simply not even possible) to match the improvement in gearing you'll get with the doubler.

So really... as downsides I see only the increased torque on the driveshafts/pinions, and that it won't improve streetability at all. Upside is that it will perform better offroad, better even than regearing to the highest you can in your axles (4.88:1 on stock axles.)
 
I am sorry that I did not say this is not a dd, I do drive it around town a couple times a month just for fun though. I understand your response and would like to ask, is the increased torque going to affect a stock geared axle differently than a geared up axle (lets say with 4.88).

As far as the driveshaft, i am using a stock front driveshaft for my rear, this should be able to handle the load right?
 
ok with 3.55 gears 2.80 1st gear and 2.72 in each case ur lookin an 73 to 1 final crawl ratio, 3.55x2.80x2.72x2.72=73.540096. soooooo if u gear to say 4.88 then ur at a final crawl ratio of 101 to 1. its technically no more stress or load on ur gear unless wedge a tire u just gotta make sure u dont just stay on the gas and snap something. truely its better and less wear on everything to have dual cases like a yota because u have waaaay more control over obstacles less chance to go to fast at an obstacle or get to stupid on the gas. trust me i had a yota with dual cases and it made rock crawling much more fun and much more in control being that it was a stick. the yotas if well done up dual cases and 4.7 gears in the rear case have a crawl ratio of 223 to 1 in first on a manual. my xj with stock case and 4.10s on a manual is 42 to 1 in 1st gear. o and also dual cases dont affect normar 2hi driving at all. in the end dual cases kick ass.
 
The benefit would be that the pinion and ring of a 3.55 gear set is much larger then the pinion and ring of a 4.88 gear set.. I don't personally see you breaking ring and pinion's with the doubler.. Shafts and U-joints are a diffrent story.. If you plan on building 60's in the future. I'd go with the doubler now and save the cash on gearing for the 60's..
 
cjsxj87 said:
If you are going to do 60s, Id prolly do a d300 with a 231 crawl box, so you can have twin sticks.
Click to expand...

x2. The 231 as a doubler is fine. The added torque is down stream. Putting a 231 behind a 231 could lend for a greanded 231. The D300 would be much more desirable IMHO. I run a 203/205 so I have been there. I ran my 4.10 D60's with 42's for a year befor regearing. In order to do anything in the rocks I almost always have to use both cases with the 4.10 gears. Aslo double tcase gears and high axle gears add stress to the driveshaft. I ate a couple over the year that I run it that way. So makes sure you have a spare.
 
I would say it might depend on the axles you have now. I wouldn't gear a d35 for lack of resale value. However if you have a 8.25 or d44 in the back, you would likely come out even on resale. d44 no gears...$250 Geared D44.....$5-600

That being said I think I would go with the axles....chances are with a doubler kit you will need new driveshafts made and then when you get your D60's in there, you will need new driveshafts again.

If you do the dana300 doubler kit you may get away with the driveshafts you already have....the addition of the second box made my out put around one inch farther back if i remember right. I don't think I would even consider doing a 231/231 setup...the second 231 will break judging by the size of tires I would expect to find on d60's
 
Actually im kinda interested in the 231 doubler. Im on 35s with a d30/44 combo locked f/r. I dont plan on going to 60s, so would it be ok to run a 231 doubler? or should I flip and build a 300? Did 300s come single sticked? Basically would it be better to build a 231 doubler or just do a 231/300?
 
If he's not DDing it, he can probably just cut down the driveshafts he already has, since it won't be seeing highway speeds balancing the shafts is nowhere near as critical.

What I'd worry about is breaking the driveshafts... carry spares!
 
kastein said:
If he's not DDing it, he can probably just cut down the driveshafts he already has, since it won't be seeing highway speeds balancing the shafts is nowhere near as critical.

What I'd worry about is breaking the driveshafts... carry spares!
Click to expand...

x2 Been there. If you want to see a doubled set up I know of 2 rigs that will be at the crawl with doublers.
 
JohnX said:
That being said I think I would go with the axles....chances are with a doubler kit you will need new driveshafts made and then when you get your D60's in there, you will need new driveshafts again.
Click to expand...

I have 2 extra driveshafts right now i don't mind cutting a couple down. I would have to shorten the rear and extend the front? Does any on know any good write ups on changing the drive shaft length? Just for the record I am a certified welder and can lay a pretty good bead. I have considered square tubing drive shafts also. Whats your opinion?
 
Ghost said:
x2. The 231 as a doubler is fine. The added torque is down stream. Putting a 231 behind a 231 could lend for a greanded 231. The D300 would be much more desirable IMHO. I run a 203/205 so I have been there. I ran my 4.10 D60's with 42's for a year befor regearing. In order to do anything in the rocks I almost always have to use both cases with the 4.10 gears. Aslo double tcase gears and high axle gears add stress to the driveshaft. I ate a couple over the year that I run it that way. So makes sure you have a spare.
Click to expand...

I could be wrong but I think that the same kit will do Dana300 or a NP231 so after I make the 231crawl box i could add it to a Dana300 later. Right now I don't have the money to buy and rebuild a Dana300 and do the doubler, but i have 3 NP231's sitting in the garage all of them are in great shape, I have ran two of them in my XJ. The other was in my brothers XJ. I know that the NP231 is less desirable than the Dana300 for strength and longevity but if I have an extra one sitting on the trailer, I don't think that it will worry me to much out on the trail.
 
Ghost said:
DOn't know that I would call it good... but: http://naxja.org/forum/showthread.php?t=1034164&highlight=rebuild

The DS would need to be shortened when you went to a different axle. I had that come up when I went form a 9" to a D60 rear. I used the same shaft on the front for a D44 to a D60 though.
Click to expand...

Thank you that is great, I think that i can handle that. That cv joint is a pain the a$$ to mess with, the first time took me forever, but now I have it down.
 
You must log in or register to reply here.

Similar threads

A
Speedo works and it's correct?
Replies
6
Views
184
Abstrastic
A
C
NP231 On My Table
Replies
3
Views
128
phydeaux33
phydeaux33
J
1989 AW4 wiring
Replies
6
Views
218
Thorwon
Thorwon
jrienzo4
Direction/Feedback Needed
2
Replies
21
Views
568
Evan03
E
D
Locker / Posi combo for trail rig
Replies
13
Views
502
Evan03
E
Back
Top