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Axle/diff/tcase question


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I’m finding conflicting info made more difficult by t being unknown what the PO changed underneath.

 

I have an 87 xj Wagoneer limited and I’m trying to figure out what exactly it’s equipped with. I know from the labels on them that I have a NP242 transfer case and AW4 transmission. I believe that is the select track package but I’m wondering how exactly it operates in terms of 4 Wheel Dr. and the differentials. I have included pictures of my axles, I’m wondering what they are. And what I should upgrade them to, if necessary.

 

Also, I’m wondering exactly how many shift positions the transfer case has. Shifter doesn’t line up with anything on the display next to handle.

94df0f317e091e3b337f4ee0f0cf333c.jpga352f12a4892a12ab2b63b43560526c8.jpg4e287b77fcecac3c0aeb0c928409c3e9.jpg93fd14367fe29874c98415642590278d.jpg

 

Also my spring on the driver side is rubbing against the, steering knuckle? I’m not sure the proper term. Any fix?

bdec1c519d52c47ee3a7783fac0e0e78.jpg

 

 

87' XJ Wagoneer I-6 AW4 NP242

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Assuming you read your tcase tag correctly you have a NP242.  The shift positions are 2wd, 4wd part time, 4wd full time, neutral, 4wd part time low range.  Note, part time means it is only to be used for part of the time, as there is no central differential action in this position, IE not for dry pavement.

 

Chances are the tcase shift linkage is all screwed up and out of adjustment because it's a terrible design.  You may be able to adjust it.

 

You've got the regular non-CAD HPD30 in the front, and a D44 in the rear.  Good stuff.

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And the spring rubbing the inner C (or inner knuckle, not the steering knuckle) is because the coil either isn't in the bucket and pinned correctly (there is clips to retain them, they strip out), or it's an aftermarket coil that's too large of an OD, or the track bar is the stock one or poorly adjusted so there is side loading on them.  Spring steel is super hard, so it's not going to wear out any time soon, but it may be able to be corrected.

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Assuming you read your tcase tag correctly you have a NP242.  The shift positions are 2wd, 4wd part time, 4wd full time, neutral, 4wd part time low range.  Note, part time means it is only to be used for part of the time, as there is no central differential action in this position, IE not for dry pavement.
 
Chances are the tcase shift linkage is all screwed up and out of adjustment because it's a terrible design.  You may be able to adjust it.
 
You've got the regular non-CAD HPD30 in the front, and a D44 in the rear.  Good stuff.



Okay that’s what I thought about shift positions...what was throwing me off is the nomenclature on the shifter display. Now when I have it in 4wheel drive one tire will spin while the others don’t...is that where lockers come in. I’m trying to understand how exactly the drive train works. Lockers refer to he hubs, correct? Would it be feasible to put lockers on the axle set I have, front and rear/ether-or?


87' XJ Wagoneer I-6 AW4 NP242
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17 minutes ago, Kyleinreallife said:


Okay that’s what I thought about shift positions...what was throwing me off is the nomenclature on the shifter display. Now when I have it in 4wheel drive one tire will spin while the others don’t...is that where lockers come in. I’m trying to understand how exactly the drive train works. Lockers refer to he hubs, correct? Would it be feasible to put lockers on the axle set I have, front and rear/ether-or?
 

 

 

 

No. The locking is in the transfer case, not the differentials.

 

With the 242 SelecTrac option, the "Part-time 4WD" position locks the transfer case so the front and rear driveshafts always turn at the same speed. It seems a bit counter-intuitive at first, but it's called "part-time" because you're only supposed to use it "part time," when the wheels are on slippery stuff. If you run in that position on dray pavement, the drive train will bind up and something will break.

 

In the "full-time 4WD" position, the transfer case engages a differential that allows the front and rear driveshafts to spin at different speeds -- such as when going around corners. This means you can use it in 4WD even on dry pavement.

 

You may (or may not) have a limited slip differential in the rear. If you do, it may or may not be worn out. Jeep never offered a locking front differential in the XJ or MJ. You can certainly install a locker or a limited slip in either the front or rear axle -- or both, if that's what floats your boat.

 

"Lockers" refers to the differentials, not to the hubs. You can have locking hubs with or without locking differentials, and you can have locking differentials with or without locking hubs.

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And the spring rubbing the inner C (or inner knuckle, not the steering knuckle) is because the coil either isn't in the bucket and pinned correctly (there is clips to retain them, they strip out), or it's an aftermarket coil that's too large of an OD, or the track bar is the stock one or poorly adjusted so there is side loading on them.  Spring steel is super hard, so it's not going to wear out any time soon, but it may be able to be corrected.

I think you’re dead on on the over sized spring, I imagine they were part of the rough country lift the PO had put on. Now for the shifter/tcase issue. When I use the lever from in the cab I can get into what feels like 4wheel full time and 4wheel lo (part time? I believe) the space in between is slack on the lever side. But when I go underneath and manually shift the tcase with a wrench, I can feel it lock nicely into more positions than are on the shifter display [maybe PO changed center console?]

The pictures I’ve seen for the Wagoneer shifter show 2, 4full, 4part, 4part lo. Mine only shows 2, 4hi lock, 4 lo lock as show in the pic above.

I have 2 indicator lights that turn on 4wd and lock. What do they mean, they turn on sporadically when I have the tcase any mode other than 2wd. The wires for the connector are a bit frayed, I suspect this is cause for the sporadic issue, but in what modes are they supposed to come on?

I’m going to invest in a Novak cable shifter in the hopes of being able to diagnose whether my tcase is working properly.


87' XJ Wagoneer I-6 AW4 NP242
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Yours being an 87 means its the first year of the 4L, and the Aw4, and the NP242.

 

The "full time" or "part time" nomenclature started up in 88 and on.

 

Basically, your "Hi lock" means "Part Time" and your 4wd means "full time",  then neutral, then your "Lo Lock" means "4 Lo part time"

 

As stated before, "Part time" means you should only use it part of the time, since the transfer case is locked, like in mud, loose or slippery road surfaces. And since yours say "Hi lock" its actually the most intuitive nomenclature out there.

 

In 88 they looked like this:

 

clip_image016.jpg

 

 

And 97+ they looked like this:

standard.jpg

 

And this is the sticker that newer jeeps have on the headliner:

 

np242_modes.jpg

 

 

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Yours being an 87 means its the first year of the 4L, and the Aw4, and the NP242.
 
The "full time" or "part time" nomenclature started up in 88 and on.
 
Basically, your "Hi lock" means "Part Time" and your 4wd means "full time",  then neutral, then your "Lo Lock" means "4 Lo part time"
 
As stated before, "Part time" means you should only use it part of the time, since the transfer case is locked, like in mud, loose or slippery road surfaces. And since yours say "Hi lock" its actually the most intuitive nomenclature out there.
 
In 88 they looked like this:
 
clip_image016.jpg
 
 
And 97+ they looked like this:
standard.jpg
 
And this is the sticker that newer jeeps have on the headliner:
 
np242_modes.jpg
 
 

So the 4wd spot on my indicator is essentially “all wheel drive?” And I should be using hi lock and lo lock for actual off-roading? When would 4wd, open diff come in handy? Also, I’m rarely on icy roads, but in that case what mode would be best?


87' XJ Wagoneer I-6 AW4 NP242
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No. The locking is in the transfer case, not the differentials.

 

With the 242 SelecTrac option, the "Part-time 4WD" position locks the transfer case so the front and rear driveshafts always turn at the same speed. It seems a bit counter-intuitive at first, but it's called "part-time" because you're only supposed to use it "part time," when the wheels are on slippery stuff. If you run in that position on dray pavement, the drive train will bind up and something will break.

 

In the "full-time 4WD" position, the transfer case engages a differential that allows the front and rear driveshafts to spin at different speeds -- such as when going around corners. This means you can use it in 4WD even on dry pavement.

 

You may (or may not) have a limited slip differential in the rear. If you do, it may or may not be worn out. Jeep never offered a locking front differential in the XJ or MJ. You can certainly install a locker or a limited slip in either the front or rear axle -- or both, if that's what floats your boat.

 

"Lockers" refers to the differentials, not to the hubs. You can have locking hubs with or without locking differentials, and you can have locking differentials with or without locking hubs.

Great info, thanks.

 

What exactly does limited slip diff mean and how would I determine if I have it and if it’s functional?

 

Also, does that mean that locking diffs and locking hubs do effectively the same thing? What’s the comparison in terms of effectiveness?

 

 

87' XJ Wagoneer I-6 AW4 NP242

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From in the cab, the shifter only locks into 2wd, 4wd and lo lock (with some finagling of the handle). It goes from 2wd to 4wd nicely but is loose through hi lock. To get it into lo lock, I have to reset to 2wd (neutral, will explain shortly) and sweep down to lo lock and it will kick in.

Going from 2wd to 4wd works but when I pull it out of 4wd it goes into either N or in between settings. To get it all the way back into 2wd I have to get underneath with a wrench and do it manually. The shoddy linkage and indicator lights make it difficult to determine what mode it’s in and I haven’t had a help to be above while I’m underneath to diagnose...

Meaning I’m only sure of being in 2wd or lo lock and can’t tell if I’m hi lock or 4wd...

For context, I’m trying to get maximum traction on uphill dirt roads without going into lo gears.


87' XJ Wagoneer I-6 AW4 NP242

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Assuming you read your tcase tag correctly you have a NP242.  The shift positions are 2wd, 4wd part time, 4wd full time, neutral, 4wd part time low range.  Note, part time means it is only to be used for part of the time, as there is no central differential action in this position, IE not for dry pavement.
 
Chances are the tcase shift linkage is all screwed up and out of adjustment because it's a terrible design.  You may be able to adjust it.
 
You've got the regular non-CAD HPD30 in the front, and a D44 in the rear.  Good stuff.

What does non cad mean? And what’s the benefit of high pinion over low pinion? Clearance? Driveline geometry?


87' XJ Wagoneer I-6 AW4 NP242
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One more thing, now that y’all have helped me identify what axles I’m working with. And I believe they will suffice for what i need, not going bigger than 35s and not dropping in a v8, just weekend warrior stuff and the occasional trip.

 

How would I upgrade them to be a bit more sturdy and give maximum torque/traction?

 

 

87' XJ Wagoneer I-6 AW4 NP242

 

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If by "a bit more sturdy" you mean stronger, you can upgrade your axle shafts. If cost is not an issue, I would get RCVs. Here's a link:

http://www.rcvperformance.com/index.aspx

 

For better torque you'd need lower gears. For instance, if your gear ratio in your axles is currently 3.54:1 you might consider 4.10:1 or 4.56:1 gears. 

 

Better traction can be achieved with a variety of lockers and limited slip differentials. Again, if cost is not an issue, I would get ARB Air Lockers - which are selectable in that they are either in "open diff" mode or completely locked. 

 

Here re is a link to the ARB site:

http://store.arbusa.com/Air-Lockers-C7.aspx

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8 hours ago, Kyleinreallife said:

 

What exactly does limited slip diff mean and how would I determine if I have it and if it’s functional?

 

Also, does that mean that locking diffs and locking hubs do effectively the same thing? What’s the comparison in terms of effectiveness?

 

 

A limited slip differential is a light to medium duty "locking" differential that's suitable for regular driving on pavement because the "locking" is accomplished with clutches that can release. When a vehicle turns, the outer wheel on an axle travels farther than the inner wheel, so the two wheels aren't rotating at the same speed. With a true locker, in tight turns this results in tires chirping and often some clanging and banging from the differential as the diff locks and unlocks. With a limited slip, on dry pavement the tires have enough traction that the torque causes the clutches to slip, eliminating tire chirp, and there is no banging. If you have it, there would have been a tag on the rear diff, but by now that might have been lost. Jack up one rear wheel and try to turn it (with the brake off and the transmission in neutral). If you can't turn it, you probably have a limited slip. However, you could still have a worn-out limited slip even if you can turn it -- the only way to know for sure is to open up the differential and look. The limited slip carrier looks very different from the open carrier.

 

Locking diffs and locking hubs are completely different. If you put a locking diff on the front axle, it creates very unpleasant driving characteristics on pavement. To alleviate this, hubs that can unlock the wheels from the axles are used. When unlocked, the wheels are free to turn independent of the axles, so the locked differential doesn't affect road manners.

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8 hours ago, Kyleinreallife said:


So the 4wd spot on my indicator is essentially “all wheel drive?” And I should be using hi lock and lo lock for actual off-roading? When would 4wd, open diff come in handy? Also, I’m rarely on icy roads, but in that case what mode would be best?


87' XJ Wagoneer I-6 AW4 NP242

 

Yes, the 4wd is like AWD. Hi lock or low is good for off-road. I will use the hi lock when snow and ice is pretty bad, but once roads are more wet and just a little snowed or I wet I goto the AWD. Even in rainy conditions the awd helps in keeping traction. 

 

When i I am actually off-roading I'm usually in lo lock, I off-road in the mountains here and I want to lower gearing the lo lock provides. 

 

You can shift on the fly to either of the 4wd hi modes. But to enter lo you need to be stopped, with the tabs in neutral, and then shift into lo lock. Likewise to leave lo you will need to be stopped with the trans in neutral. 

 

CAD refers to center axle disconnected, which your axle does not have. In the 87-90 years of jeeps if you got the np231 transfer case you got the CAD front axle. If you got the NP242 like you have you got a non CAD axle. This is a good thing as generally the CAD mechanism would break leaving you without 4wd. 

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1 hour ago, Kyleinreallife said:


Any particular reason for not replacing the z linkage? Alternates? Or just no...lol

 

DIY it with some rod ends and threaded rod, etc if you can't get the factory one to work.  Cable shifters are never that reliable, and generally give poor operator feedback, they're really a solution that is meant to be used when a traditional linkage would be too complicated to ever work reliably (typically in cases with doublers/triplers or divorced transfercases) and at $180 I just don't see how anyone could justify the Novak setup.  Boostwerks makes a linkage replacement, but that chances of it actually fitting correctly and working are very low, I also seem to recall it's quite expensive as they complicated it several magnitudes of order more than it needed to be (which is also likely part of the reason why it often doesn't work).

 

This is mine, total cost invested was under $10:

o2E4ePbh.jpg

ljOPAMsh.jpg

 

It's just a piece of flat bar which was drilled/filed to allow it to index correctly on the shift stud on the tcase, some rod ends I had lying around, and some stainless allthread I had left over from a JB Custom Fab NP205 shifter setup.  You may need to make it slightly different depending on the positioning of the tcase vs the floor/shifter, but the main thing to keep in mind is to keep the throw ratio at 1:1 and have the arm on the shift stud nearly hit the tcase when in the farthest back position (which is 2wd high).

 

I can shift the tcase with my pinky finger using this setup, and the gates/detents can be clearly felt.  Make sure your motor mounts and tranny mounts are in good condition though as it may want to pop out of gear otherwise (which is a problem with the stock setup too).

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22 hours ago, Kyleinreallife said:


So the 4wd spot on my indicator is essentially “all wheel drive?” And I should be using hi lock and lo lock for actual off-roading? When would 4wd, open diff come in handy? Also, I’m rarely on icy roads, but in that case what mode would be best?


87' XJ Wagoneer I-6 AW4 NP242

I've got the 242 tcase in my MJ. I use the full-time 4x4 (4wd on yours) any time I'm on the road an would like a little more traction on a road without compromising anything. Basically when the roads are snowy, gravel roads, basically anywhere there's low traction but inconsistently, where I'd risk binding something if I suddenly had traction again, or surfaces I don't want to risk damaging by spinning wheels, like a lawn. I've also used it while towing, to take some of the load off my turdy5 and for a little extra stability. I generally would only use 4hi (i.e. part-time, Hi lock) if I was on a surface where there was a risk one of the wheels might stop turning, like mud, larger rocks, deep snow, etc. Low range gets busted out if I need less wheel speed, more torque, or both, like if I'm stuck, trying to climb up a steep slope or a taller curb, or recovering a stuck vehicle.

One of the biggest advantages to having the full-time 4x4 option is the better handling characteristics. Part-time 4x4, with the axles forced to turn at the same speed, tends towards pretty significant understeer at any speed, and also increased turning radius at low speeds. It also will scrub the tires while turning as one tire will end up breaking loose or dragging to make up for the different radius (and required speed) each axle turns through, which will either chew up tires or the surface you're driving on, and if your traction is too good you'll build up pressure as the axles try to turn at different speeds until that pressure is released, generally by breaking something. In full-time 4x4 with a differential between your driveshafts, the front axle is still driven but is able to turn at a different speed than the rear, meaning there's significantly reduced slipping and scrubbing, no drivetrain bind, and minimal effect on turning radius (vs 2wd), and just in general similar driving characteristics to 2wd, albeit with the front tires still pulling you along. It's great for high-speed driving on loose surfaces, I'll tell you that.

Going back to the first paragraph, my full-time gets the most use on snowy roads (last season's last snowfall here was June 10th, the first one this season was sept 12th... I haven't seen the pavement on my street since some time in December), then ripping around on gravel, then for towing up steep hills or loose surfaces. There is a noticeable increase in fuel consumption over 2wd, so typically I won't use it if I don't really need to, although "need" may be a more broad definition than you'll find in the dictionary...

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The Cherokee my late wife drove has a 242 transfer case. She came from an area that never saw snow, so driving in real winter wasn't something she was comfortable with. When the first snow flew I would put it in full-time 4WD, and just leave it there until spring. It made her feel a lot more secure on the road.

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DIY it with some rod ends and threaded rod, etc if you can't get the factory one to work.  Cable shifters are never that reliable, and generally give poor operator feedback, they're really a solution that is meant to be used when a traditional linkage would be too complicated to ever work reliably (typically in cases with doublers/triplers or divorced transfercases) and at $180 I just don't see how anyone could justify the Novak setup.  Boostwerks makes a linkage replacement, but that chances of it actually fitting correctly and working are very low, I also seem to recall it's quite expensive as they complicated it several magnitudes of order more than it needed to be (which is also likely part of the reason why it often doesn't work).
 
This is mine, total cost invested was under $10:
o2E4ePbh.jpg
ljOPAMsh.jpg
 
It's just a piece of flat bar which was drilled/filed to allow it to index correctly on the shift stud on the tcase, some rod ends I had lying around, and some stainless allthread I had left over from a JB Custom Fab NP205 shifter setup.  You may need to make it slightly different depending on the positioning of the tcase vs the floor/shifter, but the main thing to keep in mind is to keep the throw ratio at 1:1 and have the arm on the shift stud nearly hit the tcase when in the farthest back position (which is 2wd high).
 
I can shift the tcase with my pinky finger using this setup, and the gates/detents can be clearly felt.  Make sure your motor mounts and tranny mounts are in good condition though as it may want to pop out of gear otherwise (which is a problem with the stock setup too).

My brain is having trouble understanding how that would work, how does it not bind up? How did you get the proper indexing?


87' XJ Wagoneer I-6 AW4 NP242
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45 minutes ago, Kyleinreallife said:


My brain is having trouble understanding how that would work, how does it not bind up? How did you get the proper indexing?

 

It's so simple that people can't understand it.  The throw ratio is 1:1 with the stock gate, the super complicated linkage that Jeep used is in fact effectively a 1:1 ratio itself.  So the length of the arm I made is (center of the shift stud to the hole for the rod end, a second hole was drilled for no reason and I have always wondered why I did) the same length as the arm off the stock shifter (center of the pivot point to the hole in it that the factory provided).  There only physical gate in the stock shifter is from the 4hi-neutral position, so as long as you're adjusted to hit that perfectly it won't matter if it is slightly out in the other positions, functionally mine lines up fine although I will admit I do not have a normal XJ/MJ to compare it to (my XJ has triple sticks).

 

One can resort to using cables, or complicated linkages with bushings, or fancy laser cut parts, but there simply is no need.

 

The stock linkage was designed to isolate NVH, and to provide some artificial feel/resistance to the setup.  With this there is only actual feel, and the only resistance is that of the detent riding over the shift cam, and the actual shift collar in the tcase sliding into place.

 

If one was not running a center console or regular interior, I would say it is preferable to not have the shifter attached to the body/chassis in any way, as there always will be issues associated with excess driveline movement in that scenario.  However, if your motor and trans mounts are in good shape, it does not present any actual functional difficulty (this is for either my linkage or the stock one, both have the same issues if the mounts are soft/torn).

 

Another note on cables is that the JK uses them from the factory.  It's a terrible setup, but very good at isolating NVH.  It also would have had a much lower per unit cost given the intended production lifespan, and very real savings regarding labour for initial installation and adjustment (or the fact there isn't any adjustment, more correctly) so they can do for a net cost of very few dollars what would cost many times as much for the aftermarket.  I've only had it freeze solid a handful of times, and fall right apart once, and that's in the span of putting 40K kilometers on my JK.  Meanwhile I can shift my MJ's tcase with no issues, and have no worry about breaking the linkage or a cable in the event it were to magically bind up...

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It's so simple that people can't understand it.  The throw ratio is 1:1 with the stock gate, the super complicated linkage that Jeep used is in fact effectively a 1:1 ratio itself.  So the length of the arm I made is (center of the shift stud to the hole for the rod end, a second hole was drilled for no reason and I have always wondered why I did) the same length as the arm off the stock shifter (center of the pivot point to the hole in it that the factory provided).  There only physical gate in the stock shifter is from the 4hi-neutral position, so as long as you're adjusted to hit that perfectly it won't matter if it is slightly out in the other positions, functionally mine lines up fine although I will admit I do not have a normal XJ/MJ to compare it to (my XJ has triple sticks).
 
One can resort to using cables, or complicated linkages with bushings, or fancy laser cut parts, but there simply is no need.
 
The stock linkage was designed to isolate NVH, and to provide some artificial feel/resistance to the setup.  With this there is only actual feel, and the only resistance is that of the detent riding over the shift cam, and the actual shift collar in the tcase sliding into place.
 
If one was not running a center console or regular interior, I would say it is preferable to not have the shifter attached to the body/chassis in any way, as there always will be issues associated with excess driveline movement in that scenario.  However, if your motor and trans mounts are in good shape, it does not present any actual functional difficulty (this is for either my linkage or the stock one, both have the same issues if the mounts are soft/torn).
 
Another note on cables is that the JK uses them from the factory.  It's a terrible setup, but very good at isolating NVH.  It also would have had a much lower per unit cost given the intended production lifespan, and very real savings regarding labour for initial installation and adjustment (or the fact there isn't any adjustment, more correctly) so they can do for a net cost of very few dollars what would cost many times as much for the aftermarket.  I've only had it freeze solid a handful of times, and fall right apart once, and that's in the span of putting 40K kilometers on my JK.  Meanwhile I can shift my MJ's tcase with no issues, and have no worry about breaking the linkage or a cable in the event it were to magically bind up...

Got it. What do you mean “physical gate from 4hi-neutral”? And did you use 1/4” or 3/16” for your replacement tcase arm?


87' XJ Wagoneer I-6 AW4 NP242
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