School me on t-cases

[LittleD]

I've had this spare np242 sitting in my shed for over a year, and with possibly going 35's on 4:10's, i figure i can make up for it by splitting the spare t-case open and doing some work.

Before i even get started, how much have people spent doing what to the transfer case? im thinking about gearing it and possibly a porc slip yoke with a front shaft.

What are reduction box's? i hear people saying they have a 4:1 reduction box and it seems to be a good upgrade.

[iant333]

Nobody makes an SYE for a 242, you have to hack and tap or go without.

The only 4:1 I know of is the teraflex one which costs about 1000 dollars and just replaces your planetary gears, plus I don't think they make them for the 242, and even if they did they are ridiculously expensive. Your only option as far as lower gearing would be a doubler, which I believe can be adapted to a 242.

The 242 is a pretty crappy choice for a wheeling rig t-case. 231 is your best bet.

[LittleD]

Is it a easy swap to go from a 242 to a 231? i know the 242 has the select trac and the 231 doesn't.

[Burton58]

they are direct swaps

[LittleD]

they are direct swaps

Thank you, so all i would need to do is change the shift bezzle and make sure the 231 has the same spline count? ( i know to look for a 87-89 because of the h.o had a higher spline count)

Edit: Chain wise, do the two cases use the same chain?

[iant333]

Thank you, so all i would need to do is change the shift bezzle and make sure the 231 has the same spline count? ( i know to look for a 87-89 because of the h.o had a higher spline count)

Edit: Chain wise, do the two cases use the same chain?

No different chain.

[customcreationsllc]

Do some internet searching it's not that hard and there is a lot of information out there. But I have a few minutes to help you out.
http://www.rsgear.com/technical/articles.asp
http://www.novak-adapt.com/catalog/t...components.htm
Pirate is always a good source too.

Nobody makes an SYE for a 242, you have to hack and tap or go without.

The only 4:1 I know of is the teraflex one which costs about 1000 dollars and just replaces your planetary gears, plus I don't think they make them for the 242, and even if they did they are ridiculously expensive. Your only option as far as lower gearing would be a doubler, which I believe can be adapted to a 242.

The 242 is a pretty crappy choice for a wheeling rig t-case. 231 is your best bet.

Correct Teraflex has a 4:1 low range kit which replaces the 2.77 low range in there from the factory. But over $1000.
They replace front housing because it is almost impossible to replace the ring gear for the planetaries.
Teraflex will do a 242 4:1 but you have to contact them and send them the housing.
Dana 300 4:1 kit is only $600

Correct no 242 SYE shafts you need to do a Hack and Tap which is essentially the same thing just a little longer.

231 is not the best bet but cheap and plentiful.

Now onto low gearing what is optimum depends on driving style and tires engine size etc.
Slower the easier and precise you can crawl, a little faster is easier for hill climbs. etc. With automatics you have torque converter slip so it feels like you have lower gearing.

I currently run with a crawl box which is like putting a second gear reduction between the tranny and T-case gear reduction gets multiplied.
I have the NP231 2.77:1 crawl box kit is like $500 in front of my D300 2.66:1 So I can choose either ratio or multiply the 2 together 2.77*2.66=7.36 so it is like I have a 7.36:1 T-case on the normal tails I'm in single low crawling I'm in double low.


Now there are 2 basic kinds of transfer cases Chain driven and Gear driven.
Chain driven: 231,241,242,247,249 etc.
the front output is ran off the rear output via a chain so the front cannot turn without the rear turning except all wheel drive T-case. Which allow the fronts to spin at a different speed. Look at it like and open differential in the transfer case instead of axle you have drive shafts. 242 is an open diff, where 249 and 247 are like having and limited slip.

Gear driven: Dana 300, NP205, Atlas
The power comes drives a gear then drives a counter shaft, so the counter shaft is always spinning. The gear driven T-case has 2 dogs (shifters) so you can select front high low neutral separate from the rear high low neutral. This is how you can do front digs.

There are some gear driven T-case that work like the chain driven they have a gear reduction in the front and you can select the 2 or 4 wheel drive but not front only. Toyota and NP203.

Now I don't know what transmission you have but the jeeps liked to keep the same bolt pattern 6 round and most use the same splines 21 or 23 short input or long. So if you can find one with the same splines they will bolt up. Or you need to buy and adapter they make a ton of different adapters Novak and Advance Adapters.

Second thing you need to look at is what side the front drive shaft is on.
All the Jeep NP are on the driver side.
The D300 is on the passenger.
But most gear driven T-case like the D300 are only splash lubed so can be flipped upside down with some shifter modification.


Options:
So changing T-case can get expensive.

You can go straight for the D300 with a flip kit no SYE kit need they already have fixed yokes and you have the freedom to shift front and rear separate so just front wheel drive if you like.

If you have the parts a lot of guys will go with a NP231 crawl box and D300 can flip the D300 over the the driver side.

Another option is the 231 which is common, they make SYE for them and if you really want you can get upgraded parts like wider chain and more pinion planetary gears.

Another is keep the 242 which is stronger than the 231 for some parts and some parts are the same. You would need to do a Hack and Tap SYE a little longer.
The 242 has larger sprockets about %50 so the chain sees %50 less load therefore a 1.5" wide chain is the 231 is equivalent to a 1" wide chain in the 242 plus the 242 has a larger spline front output and you have the option of full time.

If strength is a concern and price is getting up there anyways you can always go with an Atlas solves all the problems with a proven system.

Or with a Stack t-case which some are just customized D300.
They also make custom crawl boxes black box and klune.

If strength is an issue and you are changing your transmission anyways or you will need adapters.
NP205 is the strongest and can get even stronger with Lowmax 3:1 gears.
NP203 crawl box is the strongest crawl box.

Lovell not sure if I spelled that correct has a t-case only low range but shift under full power by pneumatics but it is like $3K.

So you have options.
If I was you and wanted to stay cheap keep the 242 or find a used 231 with a SYE.
If you want to twin stick so you can do front digs and can feel like doing some customizing get a D300 no SYE needed and you can use a 231 front yoke to get a CV rear yoke on the D300. You can also get cable shifters to make it easy to shift and flip.


Hope this helps.
If you have any other questions do some searching first then ask
~Justin

[CumminsJeep]

Justin, you are a wealth of information. holy crape

[clean4drxj]

Justin, you are a wealth of information. holy crape

x2 on that..

[GRANT]

x3.....

[LittleD]

WOW, thanks Justin. This is a daily driver and i was going to see if i could just swap out the chain for planetary gears to get a better ratio. Since i just did the 4:10's about 500 miles ago, i see it as pointless to toss them ( i know people wont by used gears cause they howl) and gear to 4:56's. I like the select trac and if gearing it is expensive, i might just keep this 242, and mess with the spare 242 a bit. I don't have that bad of vibes with the custom pinion angle on the 8.8 so i don't think i need to hack and tap just yet.

[customcreationsllc]

Ya the only way to get a better ratio in the 242 is the tera flex 4:1 kit, big money,
Crawl box is less than half the price but more work at least you have more gearing options 2.77:1 or 7.67:1 but then you might need to buy drive shafts.
You would be better off finding a 241 from a rubicon they already have a 4:1.

you cannot use the 242 as a crawl box they don't make a kit maybe now but the problem is the 242 housing is larger since the chain sprockets are larger so the 242 crawl box will get in the way of everything. But 231 are cheap. Find one with a blow chain or crack rear housing.

The H2 hummers, V8 grands cherokees and durangos also use the 242 and have the 6 pinions I tried looking what vehicle had the wider 242 chain but couldn't find one doesn't mean they don't exist. Some actually came with coolers.


I did successfully modify the 242 shifter cam to have 4low full time. I was hoping to be able to do front digs using the 242 open diff but I don't have enough rear braking power to hold the rears from spinning and that is with cutlass disk brakes on the rear. If I chuck the rear tires I can do a front dig but that is a lot of work.
I installed it in Adam's XJ that competes in RCrocs.

[ninetysix-ex-jay]

Damn Justin, that should be put into a spare thread and stickied

[HeavyMetal]

just nut up and buy an atlas

everything else is a waste of time

-zullo