AMC Eagle Den Forum

The Shop => 4X4 and Driveline => Topic started by: TheBirdman on April 17, 2019, 03:27:43 PM

Title: hooped transfer case / np242 swap discussion
Post by: TheBirdman on April 17, 2019, 03:27:43 PM
Hey all,
I would seem the gnomes operating my NP129 are about to go on strike. Ive always known this day would come, as they were pretty beat up and disillusioned when I got the car, and since then, theyve been forced to work odd hours with very little pay and no benefits. The writing on the wall has become much clearer lately.
To any unfamiliar with the history of the car, a short summary is here:
To sum up all thats gone wrong with the TC while Ive had it, Ill be brief.
when I first got it running, the vacuum system was a little boogered and it was stuck in false neutral. I hooked enough of it up to operate the actuator, and it worked, but when it was in 2wd and reverse, it produced a discomforting shudder.
The first time I drained the ATF, a bunch of silicone came with it, so I know the VC is some degree of shot.
I locked the front axle disconnect forward so I could shift on the fly, but when I actually tried shifting on the fly, the transfer case took a while to engage, made a horrible grinding sound, then clunked harshly into gear. I stopped the car to shift it after that.
A couple months ago, I was spinning snow donuts in the work parking lot, as one does when you drive an eagle and it snows 8 inches. On the left donuts, the front tire kicked up enough dense packed snow above the transfer case skid plate that it pushed the linkage back into false neutral and it slammed back into 4wd while the engine was revved up from being disconnected from the driveline. In fact it did this 5-6 times as I limped it back to my parking spot. After that, I dropped the skid plate and investigated. The linkage has a good bit of slop in it between the vacuum actuator and the shift arm. I ziptied the shift arm fully and firmly into the 4wd position, and it worked fine for another while.
Fast forward to last weekend, I was cruising lazily along the highway to my friends place, it pops out of gear and back in at 60mph. Thats a scary one. Now when I drive it around, every once in a while itll start a rhythmic driveline clunk for 5-10 seconds then go away.

Ive worked on and inspected the transmission, engine, both driveshafts, and both diffs, so Im pretty confident Ive got a really stretched chain or a few missing sprocket teeth, and since my long term plan was always to swap in a np242, it looks like Ill be hitting up the junkyards this weekend to find me a new transfer case. Ive read everything I can find on both forums, plus the wiki, and Im pretty confident I can pull it off, but when browsing around, I see a decent number of you mention that you have a 242 as well, so I was just wondering if you guys had any tips or little nuggets of wisdom for me. Were you able to swap the stock shift linkage, or did you use a novak shifter, or something else? The novak looks nice, but $180 seems a bit steep if I can avoid it. Also, what particular methods did you use for negating the slip joint problem? I was going to grab the slip joint off whatever jeep I get the tcase from, stick it on the eagle driveshaft, and disable the eagle slipjoint with a piece of pipe, like Ive seen a few others do, but in my research Ive come across a method from the jeep forums called a "hack n tap" slip yoke emliminator, in which you get a $100 kit, cut all but 1.5" of splines off of the output shaft, then drill and tap a hole in the center of the shaft, slide on the new yoke from the kit, and bolt it to the shaft. Then I could use the eagle driveshaft with no (or less) janky mods.
Anyways, thoughts? comments? tips? lighthearted discussion?

Also, as a treat for everybody, Ill do a teardown on the old one eventually and get pics of all the juicy carnage.
Title: Re: hooped transfer case / np242 swap discussion
Post by: amarshall on April 18, 2019, 10:43:08 PM
This is what I did to put an NP242 in my 1988 Eagle Wagon, with as many pictures as I could scrounge up.

Which NP242?  Mine came from a 1998 Jeep Cherokee XJ.  Not all had NP242's, so good luck finding one.  I wanted that to keep the full time 4WD capability, unlike the NP231 that seems more common. There is a huge amount of confusing information about input splines and input shaft lengths among different.  Here are my findings, but check that your car is the same: 
Physical mounting:  The NP242 will bolt right up.  You sometimes read about having problems with the speedo cable, because the Jeep NP242 has it clocked differently.  I didn't have any problem.  It was a bit tighter but I didn't need to split the T-case and reclock the tail section.

Input Shaft Seal:  This is where mine got tricky. 
Speedometer:  I used the stock Eagle speedo cable.  The Eagle housing will bolt right into the NP242 hole, and if everything else is stock you are good to go.

Front Driveshaft:  The stock Eagle front driveshaft worked fine.  The yoke on the Cherokee NP242 is the same style as the NP129.  The NP242 yoke was a hair longer, but there was still plenty of space in the slip yoke.  Since everything in the front is hard mounted, the slip yoke doesn't see much action in an Eagle anyway.

Rear Driveshaft:  I didn't need to hack n' tap or shorten the rear output of the NP242 at all.  My NP242 was the early Cherokee style with a slip yoke on the driveshaft and a big rubber boot.  On a tip from Rick/eaglefreek, I got a junkyard driveshaft from a 2WD Grand Cherokee WJ.  It was about the right length but the front yoke was wrong, so I had a shop replace it with the Cherokee style yoke.  I drove my Eagle to the shop with the NP242 in 4HI with just the front shaft connected.  No issues, but I was clenched up the whole time.  I can't swear that they didn't cut the Grand Cherokee shaft down a bit, but I didn't see any evidence of that when I picked it up.  Note that I have a 2" lift in the rear, using helper springs.  Not sure how this would affect the length of driveshaft, check this before you commit.

Shifter:  I briefly toyed with using a Cherokee shifter but gave up quickly.  Too much fiddling around.  I got a Novak SK2X which mounts straight to the TCase and therefore isn't connected to the body at all.  It comes with a long handle you can heat bend into place, and some leeway on where it goes.  If you were very clever you could simply cut a slot for the shifter, but I ended up cutting out a larger access panel.  This made it easier to adjust the shifter and install from above.  Made a mess of my carpet, but it was never that great anyway.  I used a shifter boot from a Jeep CJ I think - just looked online for one that looked about the right size.  I plan to install a bezel around the boot and clean it up, once I get some shop time again.

Feel free to ask any questions.  Here are a bunch of pictures:

This was my Cherokee NP242

Tag, for reference:

Didn't use the Cherokee front driveshaft, but you can see the yoke is the same style as Eagles.

Here is the speedo gear.  Ignore the blue one - that was a Jeep Cherokee unit that will NOT work in the Eagle.  The rest is stock Eagle stuff.  I replace the white gear, and the black housing to fix my speedo ratio.

This was the back of my 998 transmission when I took off my NP129.  The red ring is the stock seal, and the short shaft on my NP242 won't go that far.  You can see here that the seal is installed fluch on the outside, but I found that the pocket is much deeper.

So I got this extension seal from Teraflex.  This pic is trying to show that it will move the seal out about 3/4" from the stock location.

Install the seal extension one micron at a time.  Take your time and do the math to stop when it's 3/4" proud of the original location.  You can overshoot if you are not careful.

This is the shifter I used.  Doesn't mount to the body at all, just cut a slot in the floorboard where you want it.  That upper handle is bendable with a torch.

I think this is a boot from a Jeep CJ.

Go for it and cut a big panel for access.  Save the piece and bolt it back in with some 1-1/2" aluminum bar stock around the seam to create a flange.

I was fighting a deadline at this point, I need to go back and clean it up.  I'll fabricate a bezel, cover the carpet madness.

Couldn't resist...

Immediately after putting in the Np242 I drove from Atlanta to Nashville.  Picked up 2 buddies and their motorcycles, did a speed run to Arkansas.  Got onto dirt and didn't stop for 2 weeks until we got to Salt Lake City.  Without the low gear, I would never have made it up (and down) the 12,000 ft rocky dirt mountain passes in Colorado.

Do it!

Title: Re: hooped transfer case / np242 swap discussion
Post by: RallyEagle on April 19, 2019, 06:58:28 AM
This is excellent information. Thank you.  I may have to change out my 119 for 242 after I test drive my car off road.  Fun fact, NP 218's were replaced by NP 242's in humvee's.  IIRC Splines are different from Eagles but still could be adapted.  Speedo is mechanical as well.  Both have hi and low lock with internal cooling loop in series with transmission lines.

Thanks again.

Added: These have no 2 wd fork so they are full time 4 wd .  218 is a fixed bolted output and this 242 is a slip yoke.  These are typically behind TH400 and 4L80E transmissions.  Connected via an adapter plate.
Title: Re: hooped transfer case / np242 swap discussion
Post by: TheBirdman on April 19, 2019, 10:07:29 AM
aaawww sweet, thanks amarshall. Ive read through your thread a couple times now and really love what youve done with that thing. Good into on the extension seal and the rear driveshaft, I never would have found that otherwise. I may still do the hack n tap and use the eagle driveshaft though, I like the slipjoint in the middle. Whatever I decide, Ill update this thread with my findings.
Title: Re: hooped transfer case / np242 swap discussion
Post by: amarshall on April 19, 2019, 11:27:57 AM
Glad I can contribute what worked for me.  I should also do a shout-out to Rick, we compared notes on most of this stuff and he encouraged me to go for it.  Thanks buddy!
Title: Re: hooped transfer case / np242 swap discussion
Post by: TheBirdman on April 21, 2019, 07:59:03 AM
Jackpot, I returned from the junkyard with a np242 from a 99 cherokee, and while I was there I grabbed the ECU and wiring harness too.

eventually Id like to get the fuel injection running again.
I was sitting there looking over this 99 cherokee we were taking the TC out of, and looked through the pricing book, and it was only 20$ for ecus, 3.50 per foot of wiring harness
and the engine part of the harness was actually super easy to pull
so I got the harness and ecu for $50, even if I never do anything with it its worth it for all the daydreams Im having about having a fuel injected eagle
since Ive still got all the original 4.0 parts, the only things Id need to fuel inject it now would be a high pressure fuel pump, a cable linkage to run the kickdown lever for the trans, and some way to get a crank position sensor working
which  means A. get a AW4 trans, that would solve the kickdown lever issue and have a spot to mount the CPS
B. find a 42RE flexplate, which supposedly has tone rings but is short enough to not grenade the torque converter, and hack a hole in the eagle trans to stick the CPS in
or C, get a CPS relocation kit that bolts to the harmonic balancer, but costs north of $400
an AW4 would be nice, then Id have a modern 4 speed auto in it too
I believe thats what the donor jeep at the yard had, so I might go back there and get it, but its pan is smashed in, and might be in rough shape

Title: Re: hooped transfer case / np242 swap discussion
Post by: amarshall on April 21, 2019, 08:54:30 PM
Good score.  Your yards must be better stocked than the ones near me.  Nice 'Wing also!
Title: Re: hooped transfer case / np242 swap discussion
Post by: TheBirdman on April 22, 2019, 01:40:47 AM
Ah thanks, its my "ford support vehicle", a 1980 cx500 that got a similar treatment to the eagle. Bought as a parts bike, turned into a runner, and eventually stuck some good parts into.

I was doing some research today, and on the wiring front, it looks like the ECU can be rigged up to run with only the wiring for the engine sensors, plus battery positive, negative, starter, ignition, and fuel pump, and the TCU needs only the inputs from the trans, plus the TPS that is a part of the loom I already grabbed, and a kickdown cable that I wont even have to fabricate because for once Ill have all the right parts, or close enough to not matter.

Well, as things usually go, this thread will probably turn into me mumbling about entire drivetrain swaps and "them dag gum computers", so maybe I should move to a project car thread...
Title: Re: hooped transfer case / np242 swap discussion
Post by: TheBirdman on May 09, 2019, 12:41:22 PM
Sure enough, I got the transmission and most of the rest of the guts I need to do junkyard fuel injection. since the scope of this project has gone beyond a transfer case swap, Im going to most my posts to this thread:
Title: Re: hooped transfer case / np242 swap discussion
Post by: RallyEagle on June 04, 2019, 06:13:30 PM
Thanks amarshall! Your write up really made my retrofit to a NP242 easy.  Great info.
Title: Re: hooped transfer case / np242 swap discussion
Post by: amarshall on June 05, 2019, 11:33:33 PM
Thanks amarshall! Your write up really made my retrofit to a NP242 easy.  Great info.

No problem!  Glad the info helped.
Title: Re: hooped transfer case / np242 swap discussion
Post by: Vgrizzw on August 08, 2019, 11:10:41 AM
What’s your opinion of the sk2x shifter? I’ve read a mix of opinions. Great write up btw!
Title: Re: hooped transfer case / np242 swap discussion
Post by: RallyEagle on August 10, 2019, 08:34:16 PM
I know you are asking Marshall but here's mine.
Lots of adjustment holes for installation.
Fits and is compact.

Things that slowed me down:
Link rod between shifter crank arm and tcase crank arm was too long so i cut it down.
The nuts and bolts that grip the shifter are a pia to tighten. It would be nice if nuts were welded in place.
Bottom hole area on bracket that mounts to tcase stud required grinding to fit my setup.
Access to the two nuts that attach the bracket to tcase is really tight.

The tcase shifts nice with this setup and I'm glad I installed it. Saved time tabbing up my own.
Title: Re: hooped transfer case / np242 swap discussion
Post by: amarshall on August 11, 2019, 11:14:04 PM
I’d agree with RallyEagle.  It’s a nice kit, but some adjustment is expected.  I think they make the threaded rod too long intentionally, knowing that you will have to cut it down.  And there are tons of adjustment holes, which is good and bad - it may take a couple tries to nail down the right setup.

It’s also a bit expensive, but I can’t imagine a better solution.  Hanging the shifter off the T-Case itself eliminates a bunch of linkage that you see in most other designs - including most factory designs.  Most of the time the shifter handle is hard mounted to the body, and there is a complicated linkage or cable bridging from the shifter to the T-Case lever.  Even with factory setups, these are notorious for being lousy.  The SK2X is much simpler since you just cut a hole in the floor.

RallyEagle and I went slightly different ways with the hole.  He kept it minimal and made all adjustments from below.  I cut a larger access panel and was able to adjust from above - then put the panel back in place.  Made it a bit easier, but bad for the carpet!