NP231 converting to NP242

[jpony645]

JeepZZ: I don't have one yet that's why I'm looking.


Falcon: I understand that. What I'm trying to figure out is how does "part time" 4wd work on it. Is it like traction control where the computer sends more power to one wheel or another when it loses traction?

 

[falcon556]

Falcon: I understand that. What I'm trying to figure out is how does "part time" 4wd work on it. Is it like traction control where the computer sends more power to one wheel or another when it loses traction?

First PT: The transmission turns the input shaft of the TC. The turning is directly transfered to both front and rear driveshafts. If the input turns one turn, both the front and rear will turn exactly one turn. If you are on snow, ice, gravel, anything that will allow the wheels to slip a little, everything is cool.
However if you are on asphalt or similar, there is a problem. For a variety of resons such as turns, uneven inflation, tire size etc. the front and rear will want to take a different number of turns and when they can't, loads build up between the front and rear.
What would happen between the left and right side of an axle with no differential, happens between the front and rear axles because there is no differential in the PT position.
This means that you can be in PT position only when driving on ground that "gives", not all the time. (Part Time)

Thransfer cases with FT position add a differential between front and rear outputs.
One turn of the transmission depending on conditions, will mean a little more on one end and a little less on the other, as needed. Just like your rear axle does between left and right, no difference.
The transfer case differential looks a little different than a standard rear end differential, but it does the exact same thing.
Because of the differential between the front and rear output, you can use the FT any time any place with no worry that you are stressing the drive system.
Your next question might be why you need PT at all.
There are times when you can't get good traction because either end is slipping like crazy using all the power with the other end doing nothing.
In that case PT can save the day because it will force both front and rear to turn equally.

 

[Tim_MN]

The JEEP website has an animation with sound that explains the 2 types of XJ and Liberty transfer cases. The XJ and the Liberty use the exact same operating levers and transfer case names.
.
Jeep XJ 4x4 systems

 

[falcon556]

The JEEP website has an animation with sound that explains the 2 types of XJ and Liberty transfer cases. The XJ and the Liberty use the exact same operating levers and transfer case names.
.
Jeep XJ 4x4 systems

I went to the web site and now I have a question. They say that it distributes power 52% to 48%.
How does this happen?
I've had a 242 on my workbench and I rotated the input shaft in FT and both outputs were turning the same way. If I used my hand to make one output resist a little, the other would speed up.
I didn't see either the front or the rear being favored in any way.

 

[windellmc]

A standard open diff sends 50% of the torque to each wheel. By changing the number of teeth on the diff output gears you can vary this ratio. Supposedly the 48/52 split is for towing but I cannot see 2% being that important of a difference.

 

[falcon556]

A standard open diff sends 50% of the torque to each wheel. By changing the number of teeth on the diff output gears you can vary this ratio. Supposedly the 48/52 split is for towing but I cannot see 2% being that important of a difference.

Thanks for the explanation.
I was wondering if by favoring the rear they avoid steering problems in slippery conditions.

 

[MJR]

A standard open diff sends 50% of the torque to each wheel. By changing the number of teeth on the diff output gears you can vary this ratio. Supposedly the 48/52 split is for towing but I cannot see 2% being that important of a difference.

Really? How is an open diff going to do that when one wheel has no traction? Not, the wheel with no traction will get all the power and just spin.


Mike R

 

[falcon556]

Really? How is an open diff going to do that when one wheel has no traction? Not, the wheel with no traction will get all the power and just spin.


Mike R

I think I understand what he said. The way I imagine it, it is (in different form) like an open differential that has one spider gear with a tooth less than the other side. In such a case one wheel would always try to turn a little more than the other but would not as long as there is traction.

 

[MJR]

I think I understand what he said. The way I imagine it, it is (in different form) like an open differential that has one spider gear with a tooth less than the other side. In such a case one wheel would always try to turn a little more than the other but would not as long as there is traction.

Yes I see what he is trying to say. It's important to have more bias toward the rear due to weight transfer during acceleration but it's really a moot point if one wheel (front or rear) looses traction with open axle diffs.


Mike R

 

[Wiley Coyote]

Back to the original subject – you don’t need the shift gate, just the bezel insert (with 4 PT, 4 FT, etc on it). I did the exact opposite of what you are doing. I removed my 242 and replaced it with a 231. I was able to use all of my existing linkage, shift gate and Speedo assembly. The assembly (plug, shaft, gear and all) will swap between the two transfer cases. All you need to get is the bezel insert. I didn’t even bothered with the 4 x lights. The things never worked correctly to begin with. When you’re driving its pretty obvious if you are in 2 WD, 4 FT, 4 PT or 4 LO. If you are not sure, just look slightly to your right and down and see what position the handle is in. The whole job is pretty easy and can be done in a day in your garage. The top two bolts on the T-case are hard to get off (recommend a shorty gear wrench), but the rest is a piece of cake.

 

[falcon556]

The dealerships sells a wiring jumper that allows proper operation of the full time dash light after the 231 to 242 conversion (97+ XJ's). The part number is 56041612AA available from the dealer for $15.

I looked in the parts catalog and the 2001 lists the above jumper.
97 through 99 don't.
At the same time the manual for 97-01 shows a small wiring harness going from the transfer case to a connector on top of the transmission for the 242 only.
For the 231 the wires follow a bundle that takes them up and away.
My question is, if I get the jumper where do I plug it in? Is there a connector on the left aft side of the transmission just laying there waiting for me?
I have a 99 that I am getting ready to convert.

 

[carnuck]

Don't know the answer to the plug question, BUT the tag that reads NP242 has a skinnier chain (because it's most likely an earlier version) than the later NV242 (One of New Venture's upgrades along with building the HD version) Some people were using parts off the NV249 to make their own 242 into a HD version (the drum and chain are wider, but I'm not sure beyond that) Another possibility is going to a NV241 tcase (I have the OR version from an '03 Rubicon that has 4:1 stock along with fixed rear output) which was designed with diesel use in mind.
That said, I have a NV242 with AW4 to go into my being converted to auto '88 Comanche shortbed and wish they made a SYE for it!

 

[MJR]

Don't know the answer to the plug question, BUT the tag that reads NP242 has a skinnier chain (because it's most likely an earlier version) than the later NV242 (One of New Venture's upgrades along with building the HD version) Some people were using parts off the NV249 to make their own 242 into a HD version (the drum and chain are wider, but I'm not sure beyond that) Another possibility is going to a NV241 tcase (I have the OR version from an '03 Rubicon that has 4:1 stock along with fixed rear output) which was designed with diesel use in mind.
That said, I have a NV242 with AW4 to go into my being converted to auto '88 Comanche shortbed and wish they made a SYE for it!

The standard 242 uses the same width chain as the standard 231. The 249's I have seen apart have a similiar width chain to the standard 242/231. The 242's were first upgraded on the 94-up 242AMG transfer case which has the wide chain and 32 spline output mainshaft(along with other internal differences). The first use in Dodge/Jeep was 98/99 (till 03 I think it was) for V-8 equipped Durangos and Grand Cherokees only. In 02 the Liberty was added with the heavier duty 242. What can be confusing is looking at the tags because "J" means Jeep and "D" means Dodge so the only way to tell which is which is either by the part #'s or the size of the rear output. Reason why is both standard and heavy duty 242's where used in the same years of WJ and engine determined which you got.


The guy who has been running a modified (has 2wd) 242AMG since sometime in '03, Mike R

 

[casm]

That said, I have a NV242 with AW4 to go into my being converted to auto '88 Comanche shortbed and wish they made a SYE for it!

There are SYEs for both the early and late 242 cases.

http://www.4xshaft.com/conversions.html

As a 242 owner planning on doing this conversion later this year myself, I'm not keen on the deposit (which I notice went WAY the hell up in the last few months), but it is there.

 

[carnuck]

The standard 242 uses the same width chain as the standard 231. The 249's I have seen apart have a similiar width chain to the standard 242/231. The 242's were first upgraded on the 94-up 242AMG transfer case which has the wide chain and 32 spline output mainshaft(along with other internal differences). The first use in Dodge/Jeep was 98/99 (till 03 I think it was) for V-8 equipped Durangos and Grand Cherokees only. In 02 the Liberty was added with the heavier duty 242. What can be confusing is looking at the tags because "J" means Jeep and "D" means Dodge so the only way to tell which is which is either by the part #'s or the size of the rear output. Reason why is both standard and heavy duty 242's where used in the same years of WJ and engine determined which you got.


The guy who has been running a modified (has 2wd) 242AMG since sometime in '03, Mike R

The 249 I had (from a '93 ZJ with 5.2L) had a MUCH wider chain than any 231 I saw so far. Since it's always in 4x4 and all the power passes through the chain, it sure needs to be wide!

 

[MJR]

The 249 I had (from a '93 ZJ with 5.2L) had a MUCH wider chain than any 231 I saw so far. Since it's always in 4x4 and all the power passes through the chain, it sure needs to be wide!

The 249 uses a viscous coupler to transfer power so the stress isn't like that in a 231/242 that can be locked in 4wd. I just looked in the parts catalog and all 249's use the same size chain regardless of engine so I guess I'll have to pull the 249 sitting in my garage apart to satisfy my curiousity. May be the ones I have seen were 247's but the 247 is basically an updated 249. Ok I have something to interest me. I can compare it to the 242 and 242AMG chains.


Mike R

 

[alpinetiburon04]

So here's a crazy newbie question: I've got a 91 4x4 and htought I had all time 4wd. Now after reading this thread I'm not sure. The transfer case shifter in my Jeep has 2H 4H N and 4L on it. I've never really played with it, but now I'm thinking I only have part-time 4wd. What the hell is the 4Lo for? Towing? Wouldn't you want all time when you're towing something?

 

[casm]

So here's a crazy newbie question: I've got a 91 4x4 and htought I had all time 4wd. Now after reading this thread I'm not sure. The transfer case shifter in my Jeep has 2H 4H N and 4L on it.

You've got the NP231 with NO full-time mode.

I've never really played with it, but now I'm thinking I only have part-time 4wd. What the hell is the 4Lo for? Towing? Wouldn't you want all time when you're towing something?

4LO is for serious off-road work - climbing, descending, ploughing through thick mud, now, or sand, etc. You could conceivably tow with it, but if you find that you *have* to use it to tow, you're probably exceeding what the vehicle is rated for.

FWIW, I trailered a total weight of approximately 3500lbs. about 45 miles a couple of weeks ago. Never used 4FT - it was dry out, and 2HI seemed to be coping just fine on its own.

 

[MJR]

So here's a crazy newbie question: I've got a 91 4x4 and htought I had all time 4wd. Now after reading this thread I'm not sure. The transfer case shifter in my Jeep has 2H 4H N and 4L on it. I've never really played with it, but now I'm thinking I only have part-time 4wd. What the hell is the 4Lo for? Towing? Wouldn't you want all time when you're towing something?

Select-Trac (242) Full-time was an option. Sounds like you have the Command-Trac (231) Part-time transfer case. Using Part-time on the street can damage the unit (stretch the chain and slip on the gears).

When you need the extra torque multiplication or control at low speed off road.

2wd is just fine for towing but say you backed down a ramp to load the boat up and pull it out but your rear wheels just spin. Putting it in 4wd or low can use the front wheels to help pull you and the boat up the ramp.

I'd think 2wd is better for street towing due to less load on the drivetrain (fuel useage/wear).


Mike R

 

[carnuck]

That should read "using a Command trac on dry, good traction surfaces is very hard on them"