NV242 Select-Trac Tech

I've been searching through the archives on and off over the last 6 months or so trying to find a good source of info on this transfer case.

I was hoping that everyone could add what little they know about this case to this thread so that we have all the information in one place.

Your personal experiences (not "my sister used to date this guy and his brother had a NV242 behind a BBC...") about the case would be good to include also.

I'll get the ball rolling with what little I know about this case.

NV242 Transfer Case:

• 4 different modes
  • 2 wheel drive high
  • 4 wheel drive high part time (i.e. diff locked)
  • 4 wheel drive high full-time (i.e. diff open)
  • 4 wheel low part-time (i.e. diff locked)
• has lockable center differential
• chain drive front output
• helical planetary gear reduction
• center differential torque split is 48% front, 52 % rear
• high range is 1:1
• low range is 2.72:1
• Max torque: 1486 lb-ft / 2015 N-m
• uses ATF4 as lubricant
• Only hack-n-tap" style SYE available.

Differences between the 242J in a XJ versus a Hummer

• Hummer version does not have 2 heel drive high mode
• Max torque: 2340 lb-ft / 3173 N-m

Differences between the 242J in an XJ versus a Dodge Durango (NV242D? HD?)

• Durango version has a remote cooler

The NV website also lists a NV242HD which is different from the NV242J and the NV242HD-AMG. It's max torque rating is 2028 lb-ft / 2750 N-m. Is this the Durango unit?

What in the above list is wrong? What is missing? What "cool mods" can be done? Any mix-n-match between the 242J/HD/AMG possible?

In usage I find the NV242J (MY01) does everything I want it to do. I haven't wheeled it yet - just moved some heavy trailers on soggy ground that the 2WD PU can't deal with here on the farm, little bit of forest road trailing . Sometimes I find it does not want to shift out of 4wd to 2wd without letting it coast at speed in neutral. Sometimes 4WD low is difficult to engage when stopped in neutral. Otherwise it feels "solid".

Who has the TeraFlex 4:1 kit installed?

What changes were there throughout the years?

r@m

That's more info than I know! And I'd like more, since I'll be screwing with a 242 sometime in my future also.
I don't think the Tera 4:1 is available for the 242????? But I am far from an authority.
What else is known out there???

Several manufaturers offer SYE's and I believe there is a replacement shaft out also - I am pretty darn sure you have to send the front half of the case to tera for the gear set mods (but not 100% sure)... I use RE hack and tap.

I run the case and really have no isses with it - I have broken a mainshaft right at the speedo gear spiral but that was due to a spring wrap problem that bound up a 1350 U-joint (any takers on who was going to win that battle - hint the joint lives on to this day)

And I have worn out two chains in the last 7 years - otherwise no issues; occasionally it is a pita to get back into 2wd (usually something else is binding: fully welded/spooled diffs and 4 - 8 psi in the tires) Back up a bit and then pull foward usually fixes the problem....

Otherwise happy trails

Matt

You covered a lot about the 242,

The Hummer 242 also has a cooler

It is physically larger than the 231, quite a bit bigger in fact.

I have had 2 Jeeps with 242's. The first one I had needed a new chain at 60,000 miles. But I found that the case had a crack and was empty of oil. The 242 in my present Jeep wore out the range mode fork pads, which in turn wore out the range mode slider which caused it to keep dropping out of high range. This happened in the Middle of Nebraska on the way home from UT. When I returned home I bought a t-case from a Grand and swapped out my old one. In the last two Cherokee cases the front output shaft and gear were two pieces. On the grand case they were one piece. I would think the 1pc is stronger.

I am sure there is a way to make a new shift cam to give yourself 4wd low.

Also I have thought about adding a cooler to mine. I would think it would be a fairly easy mod but would cool the fluid directly unlike the Hummer cooler which uses a heat exchanger type setup.

B-loose

You should check out the latest issue (April) of JP magazine. They do a write up on the 242. They also mention that Tom Woods makes a tail-shaft conversion kit for the 242.

Not to hijack your post....

What is the difference between the 242 that goes in an 88' Wagoneer, and the 242 that goes in a newer XJ?

Also, what happens when you install a front locker? And why?

88woody said:

You should check out the latest issue (April) of JP magazine. They do a write up on the 242. They also mention that Tom Woods makes a tail-shaft conversion kit for the 242.

Click to expand...

It's just a stock shaft hacked & tapped that Tom Woods has machined.

88woody said:

You should check out the latest issue (April) of JP magazine. They do a write up on the 242. They also mention that Tom Woods makes a tail-shaft conversion kit for the 242.

Click to expand...

Will do, thanks!

88woody said:

Not to hijack your post....

What is the difference between the 242 that goes in an 88' Wagoneer, and the 242 that goes in a newer XJ?

Also, what happens when you install a front locker? And why?

Click to expand...

I know nothing about the changes throughout the years. This is somewhat important to me because my case has a small leak and I've picked up a MY89 partster truck for the t-case and .... My XJ is a DD so I was thinking this would let me do the swap of leaking to fresh in an afternoon. Then I can redo the leaking case to go into my CJ7 project.

For front locker what I've heard is that in full-time mode steering can feel pretty weird/dangerous if you are running at normal highway speeds. power delivery switching from side to side with steering changes or something like that. I bought an ARB to get around this. Hope to install in a few weeks.


r@m

Matt said:

And I have worn out two chains in the last 7 years - otherwise no issues;

Click to expand...

What kind of mileage are we talking? Just curious.

r@m

88woody said:

Not to hijack your post....

What is the difference between the 242 that goes in an 88' Wagoneer, and the 242 that goes in a newer XJ?

Also, what happens when you install a front locker? And why?

Click to expand...

I have run a MIT SYE in my 242 for four years. No issues. My XJ has 100K miles and was first modified at 20K miles. I've been running 33" plus tires for 50K miles.

The old 242 had the design where the main shaft slip yoke was encased in the housing. Late model designed had it outside the housing. Same as the changes in the 231. Means you need a SYE at a lot less lift than an 88.

When you install a front locker you get positive traction from both front wheels :looser: . This will allow you to run more difficult trails.

In full time 4wd mode, you'll have a front locker engaging and disengaging, which you may not like very much.

I run in full time 4wd a lot even at 8" of lift since I deal with a lot of snow. With a rear Detroit and front True Trac, it offers amazing snow performance, and on dry pavement it increases handling and stability noticeably. I have a front D44, however, with correct pinion/caster so it runs with no vibes even at 65 mph. I am waiting for Tractech to redesign the Electrac so I can have the best of all worlds (True Trac that locks for offroad with the actuator inside the diff).

Bottom line: most people with a lot of lift who don't have a custom front axle find full time 4wd to be useless because of front driveline vibrations, and this makes the 242 a liability. Many swap the 242 out for the stronger, smaller, and lighter 231 and install a heavy duty SYE, which is not available for the 242, for this reason.

Nay

So what exactly is the difference between the 242's diff locking (4 Part-Time) and an aftermarket locker? I've been told the 242's locking is not "true" locking, whatever that means...

The 4.1 gear set does fit into the 242 from Tera, it says to call them for more info on their website. I also remember seeing years ago that there was another company that sold 4.1 for the 242, if I remember right it was ORGS that had them but not sure. Juice

XJVenom said:

So what exactly is the difference between the 242's diff locking (4 Part-Time) and an aftermarket locker? I've been told the 242's locking is not "true" locking, whatever that means...

Click to expand...

The locking function of a transfer case has nothing to do with a differential locker.

Full time 4wd is better known as "all wheel drive". In this mode, power is transferred between the front and rear axle at a variable rate depending on conditions. In the 242 this is a mechanical function - in many newer AWD applications it is controlled by computers.

"Locking" a transfer case into four wheel drive ("part time") means that power is distributed 50/50 to the front and rear axles. This is why it is called "part time". You can't run it on dry pavement without massive driveline binding. Full time allows "slip" between axles to relieve the binding issue. The 242 "locks" exactly like the 231, i.e., it has a part time 4wd mode in both high range and low range.

A "locker" in the differential prohibits wheelspin between the two wheels on an axle. In order to get true four wheel drive, you need a locker in both axles to force both wheels to turn, and you need a locked transfer case. A stock XJ is essentially two wheel drive, in that if one wheel on each axle loses traction you are stock. An AWD car (or a 242 mode XJ) is one wheel drive because there is no locking transfer case, and the center differential cannot overcome the complete loss of traction at one wheel at very slow speed (although some new AWD systems have a push button lock mode).

Hence the advantage of the 242 is full time 4wd on the pavement with all of the features of the 231 case for more severe conditions.

Nay

Nay said:

I run in full time 4wd a lot even at 8" of lift since I deal with a lot of snow. With a rear Detroit and front True Trac, it offers amazing snow performance, and on dry pavement it increases handling and stability noticeably. I have a front D44, however, with correct pinion/caster so it runs with no vibes even at 65 mph. I am waiting for Tractech to redesign the Electrac so I can have the best of all worlds (True Trac that locks for offroad with the actuator inside the diff).

Click to expand...

Since you are running a lot of lift, you will hopefully be able to answer this question.

When you lifted your XJ was there a point at which the front prop shaft angle became out of whack and caused vibration when running at highway speeds in FT mode?

Maybe you lifted incrementally and know exactly where that limit is?

I am planning on moderate lift (RE4.5") but if it means losing the ability to throw the t-case into FT mode all winter long I will revisit that plan.

r@m

Root Moose said:

What kind of mileage are we talking? Just curious.

r@m

Click to expand...

About 80,000 miles - probably 25,000 - 30,000 was in 4wd - one of the chains died due to lube failure and the second was a used unit that was swapped from another case along with the matched sprockets - it just plain wore out to the point it started skipping - the latest has been in for the last 3 or 4 years...

Matt

Root Moose said:

Since you are running a lot of lift, you will hopefully be able to answer this question.

When you lifted your XJ was there a point at which the front prop shaft angle became out of whack and caused vibration when running at highway speeds in FT mode?

Maybe you lifted incrementally and know exactly where that limit is?

I am planning on moderate lift (RE4.5") but if it means losing the ability to throw the t-case into FT mode all winter long I will revisit that plan.

r@m

Click to expand...

My D30 stopped working well for me once I went over 3.5" of lift (I had OME plus a 1.75" budget boost). At 3.5" it was fine. At 6", the front driveshaft vibrated horribly even in 2wd. I couldn't get caster low enough to cure it without causing tracking problems. I dropped my lift to 5" to try to cure this problem, but it wasn't low enough. Full time 4wd at any speed over 25 mph was unusable for a couple years while I went through these iterations.

4.5" is probably the borderline. You'll need to drop caster to about 4 degrees to make the front driveline run smoothly. Some XJ's seem to do ok with this, but mine didn't. I needed closer to 5 degrees for it to track properly on the highway. With long arms and the D44 I run about 3 degrees of caster, which is perfect for this setup, but was unusable with short arms and the D30.

Keeping full time 4wd available at highway speed for use in the Colorado High Country during winter was a major factor in deciding to do a front 44 so caster and pinion would be properly set - I couldn't find anybody who would rotate my D30 knuckles.

I'm probably the only XJ'er on the planet with 8" of lift who regularly runs the 242 in full-time for long durations. I have Warn hubs but don't really need them from a vibration perspective...but they keep things surprisingly quiet in 2wd. I think that full time adds so much safety for my usage (family onboard in bad weather on high altitude backcountry roads) that it's kept me from ditching the 242 for an Atlas II.

Nay

Root Moose said:

Since you are running a lot of lift, you will hopefully be able to answer this question.

When you lifted your XJ was there a point at which the front prop shaft angle became out of whack and caused vibration when running at highway speeds in FT mode?

Maybe you lifted incrementally and know exactly where that limit is?

I am planning on moderate lift (RE4.5") but if it means losing the ability to throw the t-case into FT mode all winter long I will revisit that plan.

r@m

Click to expand...

Because of the unit bearings your front driveline spins all the time so you would have vibrations in all modes not just full time 4wd - under power - ie: part time 4wd and fulltime 4wd you may have less vibration if the driveline has a worn slip but angularity should not change...

Matt

Matt said:

Because of the unit bearings your front driveline spins all the time so you would have vibrations in all modes not just full time 4wd - under power - ie: part time 4wd and fulltime 4wd you may have less vibration if the driveline has a worn slip but angularity should not change...

Matt

Click to expand...

That's true - it should vibrate no matter what the mode. In my case, in 2wd it would not vibrate until high speed. Mine was fine until about 65 mph, and then it had a cyclical harmonic vibration (a droning sound that comes and goes rhythmically...exactly what you expect from a misaligned u-joint). At about 80 mph, it stopped vibrating.

In 4wd, the vibration was a constant, harsh grinding that occured anywhere from 25 mph on up, and on any heavy acceleration. Interestingly, some other 242 owners have reported far less vibration in full time mode than in 2wd, and therefore ran in full-time all the time.

One option you have is the caster correction ball joints. They are expensive, but can add back two degrees of caster (loctite those babies or they will rotate and you'll be inadvertantly adjusting camber). That would be plenty at a 4.5" lift. I had problems with lower ball joints wearing out after installing the alignment ball joints, so I finally sold my D30 off. I think it has changed hands in Colorado 3 or 4 times since.

Nay

Ok, I follow what you guys are saying.

I have a bare HP housing, Warn hubs (5 on 5.5"), ARB locker and 4.56 gears sitting in boxes. The housing is currently bare; only cost $20 so if I pooch it there is not a huge loss of money.

My current, running axle is stock (MY01 LP D30, 3.55, stock hubs).

To give an idea of my fab skills, I don't see making a truss for this axle and getting a professional to weld it up after I tack it in place as any big deal. I'm fairly certain I can rotate the knuckles myself.

I want to run the RE4.5" lift and 32x11.5 tires (maybe 33x10.5 - we'll see). I have an ARB with winch and will be getting a rear bumper, rails, etc. I expect that in completed form I will be sitting at a true 4.5" even with the RE lift (they seem to be higher than advertsied, probalby due to equipment expactations from RE).

In this situation, what should I rotate the knuckles to in order to end up with a "smooth shaft" (LOL) and decent caster? Will the change from LP to HP more or less negate any vibration and caster problems?

Any speculation?

I REALLY need this Jeep to be able to run FT mode continuously in the winter.

Thanks!

r@m

Any more info on changes to this t-case throughout the years?

The slip yoke changed in 1997?

r@m

Root Moose said:

In this situation, what should I rotate the knuckles to in order to end up with a "smooth shaft" (LOL) and decent caster? Will the change from LP to HP more or less negate any vibration and caster problems?

Any speculation?

I REALLY need this Jeep to be able to run FT mode continuously in the winter.

Click to expand...

The HP axle will not help with caster. Both axles have the pinion yoke set directly in line with the driveshaft in conjuction with about 7 degrees of caster. With either axle, you lose caster as you lift, unless you begin to create an angle in the axle end u-joint of the driveshaft, which of course causes vibration.

For 4.5" of lift you want to rotate the knuckles about 3 degrees. A general consensus on the topic a few years back was that 5.5 degrees of caster was about right for a 5-6" lift, so 3 degrees of rotation will leave the resulting caster somewhere in the 5.5 degree range. You won't know until you measure, and I wouldn't touch it without being able to measure existing caster with a perfect driveshaft once the new lift is installed. If you end up with say 3 degrees of caster, then rotate the knuckles 2.5-3 degrees.

I couldn't find a shop to rotate my D30 knuckles. They all told me you'd have to cut off the coil mounts in order to do it properly. Let us know how it turns out...I've heard a lot of people say they can turn the D30 knuckles, but I don't think I've ever seen a successful report on such a project.

Nay