NP 231 and NP 242 TC Differences

[HOrnbrod]

Been researching a 4WD conversion and got the following info from the Yahoo Strokers group regarding T-cases. Posted by hsalf625. Good stuff:

 

There are quite a few differences between the NP231 and the NP242 cases as they are completely different models. The first number is the number of ratios or ranges. Both are a 2 indicating a low range and high range. The second number is the torque rating scale. The 231 has less torque. The reason is that the 242 uses 6 pinion gears in the planetary for low range and the 231 has only 3. Additionally the 242 has a 1.25" wide chain for the front yoke while the 231 chain is 1.00". The last number indicates the type of inter axle differential if any. 1 indicates a part time only 4wd. 2 indicates an open interaxle differential for full time 4wd that is lockable for part time 4wd too. 9 is a viscus clutch full time as in the NP249. Thus the 231 or the 242 should ever slip since there are no clutches to slip. The NP242s are not as common and are in higher demand making them more expensive in salvage yards if you can find them. Shifters are different for the 242 as it has 5 detents compared to the 231's 4 detents, so a longer throw on the rod is required. The 242 is slightly longer in some versions as well. Some Dodge 4WDs used a NP231 HD TC which used the wider chain. It fits in the same 231 case to.

 

No brainer as I see it - I'll be going with the 242 in my 91 since the spline count fits too w. the 91 AW4.

[Blue88Comanche]

good to know :thumbsup:

[jeepdoggydogB]

Great info! I believe Tom Woods makes a great SYE kit for the 242 if someone wanted to go with a SYE option.

[johnj92131]

Don,

 

Good information. But, given your use of the Comanche, why consider the 4 x 4 swap?

 

I have thought about doing the 4x4 conversion on my 91 Comanche, but I only use the truck 3K per year. I have a 4x4 2000 Isuzu Rodeo, and only took it on one long winter trip because of the 4x4. Saw lots of 4x4 suv's in the ditch on 300 bad miles of that winter trip. So why do the 4x4 conversion on a street driven truck? Other than just because it is my toy!

 

 

Been researching a 4WD conversion and got the following info from the Yahoo Strokers group regarding T-cases. Posted by hsalf625. Good stuff:

 

There are quite a few differences between the NP231 and the NP242 cases as they are completely different models. The first number is the number of ratios or ranges. Both are a 2 indicating a low range and high range. The second number is the torque rating scale. The 231 has less torque. The reason is that the 242 uses 6 pinion gears in the planetary for low range and the 231 has only 3. Additionally the 242 has a 1.25" wide chain for the front yoke while the 231 chain is 1.00". The last number indicates the type of inter axle differential if any. 1 indicates a part time only 4wd. 2 indicates an open interaxle differential for full time 4wd that is lockable for part time 4wd too. 9 is a viscus clutch full time as in the NP249. Thus the 231 or the 242 should ever slip since there are no clutches to slip. The NP242s are not as common and are in higher demand making them more expensive in salvage yards if you can find them. Shifters are different for the 242 as it has 5 detents compared to the 231's 4 detents, so a longer throw on the rod is required. The 242 is slightly longer in some versions as well. Some Dodge 4WDs used a NP231 HD TC which used the wider chain. It fits in the same 231 case to.

 

No brainer as I see it - I'll be going with the 242 in my 91 since the spline count fits too w. the 91 AW4.

[HOrnbrod]

So why do the 4x4 conversion on a street driven truck? Other than just because it is my toy!

You answered your own question John. :D

[johnj92131]

So why do the 4x4 conversion on a street driven truck? Other than just because it is my toy!

You answered your own question John. :D

 

Only thing that made sense to me!! Go for it and lets all enjoy our toys!!

[Jeep Driver]

For those of us who live in the mountains 4x4 is a MUST have, not a luxury or toy item.

 

Steep gravel drives and snow and mud etc....

[jimoshel]

[Bounty Hunter]

Anybody have the actual torque handling ratings of each t-case? I vaguely remember the 231 having a higher rating than the 242.

 

I built my current 231j with a 6gear planetary, wide chain, SS sye, and 2lo. It can handle tons more torque than my 4banger can throw at it.

[Eagle]

There are quite a few differences between the NP231 and the NP242 cases as they are completely different models. The first number is the number of ratios or ranges. Both are a 2 indicating a low range and high range. The second number is the torque rating scale. The 231 has less torque. The reason is that the 242 uses 6 pinion gears in the planetary for low range and the 231 has only 3.

Interesting, but incorrect.

 

Several years ago, when they were still called New Process, NVG had a chart on their company web site showing the torque rating for most of their transfer cases. (It didn't include some of the older "legacy" cases like the 228 and 229). The 242 was rated by the manufacturer as weaker than the 231. It wasn't a lot weaker, but it was weaker.

 

I wonder if the info you found is perhaps referring to the 242HD such as used in (IIRC) Dodge pickups?

 

From Novak Adapters:

 

The design of the 242 is fairly good. They were engineered for durability and simplicity of build - both an advantage to the OEM assemblers as well as individuals servicing them. The NP242 transfer case has turned out to be stronger than expected. Most of our customers choose to retain their Jeep 242 with their conversions. It is very common for them to offer good service behind some of the strongest engines and transmissions.

 

The 242 weighs about 85 lbs.

 

This transfer case is identified by its red and silver tag on the rear of the case. They are also easily identified by appearance. They feature a six-bolt front face and a longitudinally ribbed barrel case.

 

There is a GM version of the 242 as used in the H1 Hummer (1990- ) and the later H2. It features a different front face bolt pattern that is incompatible with the Jeep six-bolt styles. This GM version is rated at a stronger duty by virtue of its stronger output shaft. It may feature a 1" wide or a 1.25" wide chain.

 

Interestingly, New Venture documents show the 242 as being rated at 1486 ft. lbs. of torque. This is probably determined based on Full-Time position usage. Experience would say that this is a very conservative number for all other positions.

 

Also from Novak (for the 231):

 

Heavier-duty HD and DHD units are available in ZJ Jeeps and Dodge trucks, respectively. The standard duty OEM 231 transfer cases are capable of transferring from 1600 to 1900 ft. lbs of torque (as claimed by NVG - actual experience puts this number quite a bit higher).

 

Wide chains, larger planetaries and stronger mainshaft/tailhousing assemblies (see Tailhousings, below) are also available if even more strength is desired. With such upgrades, a transfer case capable of handling 2900+ ft. lbs. of torque is attainable. This is a result of good engineering and refinement.

FWIW, some of the guys in NAXJA-NAC had pretty well-built XJs with stock 242 cases and nobody ever broke one, even when doing serious rock crawling at Paragon on very large tires. If I were doing a 4x4 conversion I would very much prefer the 242 ... but don't fool yourself that it's stronger than the 231. It isn't ... unless you modify it internally.

[carnuck]

The 4 in the middle isn't a strength rating. The 249 in Grand Cherokees is a weak POS compared to a NP208 or 231

[mvusse]

AFAIK, the 249 was only available in the V8 models but I may be wrong on this. If it is a weak pos, why would they only use it behind the larger engines?

 

I have never heard of someone grenading a 249, though. The problem they have is when the viscous coupling fails/wears out due to age, full time 4wd starts to act like part time 4wd. Most people swap in a 242 when this happens because a new viscous coupling to fix the 249 is $500 whereas a used 242 can be had for a lot less.

[jimoshel]

Don,

 

Good information. But, given your use of the Comanche, why consider the 4 x 4 swap?

 

I have thought about doing the 4x4 conversion on my 91 Comanche, but I only use the truck 3K per year. I have a 4x4 2000 Isuzu Rodeo, and only took it on one long winter trip because of the 4x4. Saw lots of 4x4 suv's in the ditch on 300 bad miles of that winter trip. So why do the 4x4 conversion on a street driven truck? Other than just because it is my toy!

 

 

After every major snow storm we have 90% of the cars and trucks in the ditch are 4WD and over half of them are on their roof with all 4 wheels in the air. A good set of snow tires, even in Alabama, and common sense will drive circles around a 4WD and a idiot.