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Discussion Starter · #1 ·
All you experts can have a good laugh when your done reading this but I don't care, I have to learn someway, at least I admit I'm pretty ignorant but I don't want to be and am getting less and less each day. Anyway, what exactly is so different about a XJ and a XJ with command trac. Is it a different type of transfer case or what? Alright laugh it up than ya can respond if ya want.

Jeff

 

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Jeff,

good question, and often asked, no laughing here. Run a search for the topic, we have covered it MANY times man.

have fun,

Todd



88' XJ
3" rusty's
1.75" Shackles
2" RE spacers.
Rusty LCA's.
RE adj trackbar
 

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Jeff, I take it that your 86 has Command Trac.....for your year XJ, like mine, that means a NP 207 transfer case. Command Trac is a part time 4wd system, meaning that it cannot be used on dry surfaces. If you engage the 4wd on a dry road surface and leave it in 4wd more than just a short while, you can damage it. On the plus side, Command Trac is more capable off road than Select Trac is.

Select Trac is the full time 4wd system. For our year XJ, that means a NP 228 transfer case. Select Trac can be used at any time on any on or off road surface. You could run it in 4wd 100% of the time and not damage it. It is by far the best system to use on rainy, snowy and icy roads. However, on low traction off road conditions, it could bog down. It is not as good as Command Trac in that case. /wwwthreads_images/icons/smile.gif
 
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Discussion Starter · #4 ·
So your telling me that it sucks in the snow. That [censored] blows cause I ski like 80 times a year and most of the time there is a lot of snow on the road. Is there something I can do to make it better in the snow.

Jeff
 

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No, the Command Trac will work in the snow....the difference is that the Command Trac could be dangerous if driven at high speeds on snowy/icy roads; the Select Trac is much safer in that case. So if you are careful with the Command Trac, the Cherokee will get you to the slopes. Sorry I didn't clarify that.

 
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Discussion Starter · #6 ·
So as long as I take it a little slower than the speed limit and it is in 4 wheel drive (which is better hi or lo I never learned the difference) than it won't fish tail and slide out of control? If ya can give me any pointers on driving it in the snow I'd be grateful. I have only taken it in the snow a few times and did alright (because I got it at the end of the winter). Also do beefy snow tires make that much a difference? Thanks XJ

Jeff

 

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For snowy roads- Cooper makes the best tires! Low range will make your engine spin 2.72(or whatever your transfer-case ratio is) times more for each turn of the tire. This means you'll get nearly 3 times the power at one-third the speed.

 

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Yes, snow tires would be better but most all terrain tires and all weather radials are almost as good. Probably the best are the Blizzak tires but expensive.

The trouble with any part time 4wd system on snowy and icy roads is that the front and rear driveshafts are locked together and must spin at the same speed. If you should lose traction in all four tires (pretty common on icy roads especially) then all four tires will spin. The gyro efect will send the Jeep sideways, completely unsteerable. At slow speeds, you might be able to stop but at too fast a speed, you'll end up in the ditch or worse. The word is: CAREFUL!!

Select Trac transfer cases have a differential in the case itself. This differential, similar to the ones in the axle, allows the driveshafts to turn at different speeds, depending on the traction condition differences that each axle is experiencing. By doing that, it is more less likely to "crab" sideways. Even still, it is always best to be careful and go at a safe speed. Four wheel drive is not the same as four wheel stop./wwwthreads_images/icons/crazy.gif
 
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Discussion Starter · #9 ·
Thanks for telling me that, this I did not know before. Do you think I would be better off getting good snows and just going slow? I dont care about expensive I do a lot of winter driving, I am a ski instructor in the winter and avid skier, I travel a good 5kmi + during the winter months. Should I sell this XJ and get one with Select Trac because I want this Jeep as my winter car, but if a front wheel drive or a Select Trac system is better please tell me.

Jeff

 

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Or you could just put a select trac x-case (NP-242) and driveshafts into this Jeep.... The 'case will bolt up where the old one went, the linkages should work just fine, and the driveshafts for a select-trac (or you can get new ones) only take 8-bolts per 'shaft to install.

 
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Discussion Starter · #11 ·
Your telling me I only have to remove and re-install 8 bolts? It is probably more complicated than that. Could you respond with how to do it, as indepth as possible would be good, what kind of equipment if any I need, average cost and if I myself could do it. I am not a mechanic by any means but I do know some stuff and am learning everyday. With help I would surely give it a shot if it means a safer and more reliable winter and at a small cost. Thanks for the help.

Jeff

 

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Jeff, I think that you are better off selling the 86 and getting a newer model XJ, one with Select Trac. The NP 242 Select Trac transfercase that Schyo15 mentioned is a more modern version than the one that came with the 86. It has both part time and full time 4wd selections; so it is the best of both worlds. Swapping in a transfercase yourself might be a bit too advanced for you at your current level of experience. If I remember, you are already considering selling the 86 any way. If you do a lot of winter weather driving, then it would be a good idea to buy a set of winter tires, along with a set for the other seasons.

Keep asking questions and we'll be more than happy to help. Good Luck!!/wwwthreads_images/icons/smile.gif
 

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No, the eight bolts are for the driveshaft. The tough part is the new transfer case. Although a tough task, you would learn a lot and have that great sense of pride. You would also overcome the fear of not understanding what you're doing. This all worked out for me when I pulled, rebuilt, and reinstalled my own engine.

Unfortunately, you need a pretty decent set of tools, a lift (or good jack-stands), and a good service manual to help you along your way. If your up to the task, we can help you by our knowledge, but it will put your Jeep into submission as you change t-cases. It also costs money -- probably about $200-450 for a good t-case.

If I didn't have a Jeep, I wouldn't have a life.

'88 MJ SporTruck
Rebuilt 2.5L: 40 over rings, 10 on crank, 10 on bearings
nearing 400K
 

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Its not hard to change x-cases (at least not between the NP/NV cases used in Jeeps). Its what, 8 bolts per driveshaft (16 tiny bolts, but due to the slip-yoke design you can just remove 12...) and six bolts for the x-case itself. Seven if you count the speedometer cable. Here's how to do it.

You'll need a nice set of wrenches and ratches, those ratching box-end wrenches would be nice too...I love my set. A hydraulic floor jack, 4 tall jackstands, an oil drain pan. A really huge wrench, like 1.5", or a pipe wrench that adjusts that large. Thats about it I think

Step 1:
Jack the Jeep way up and stick it on the jack-stands. Use a wrench to take the speedometer cable off the rear of the x-case (its the only cable that goes into the x-case back there...) There should also be a vent line, and I think some electrical or vacuum lines run into it- pull them all off. Disconnect the shifting linkage from the x-case's shift-arm.

Step 2:
Unbolt the front driveshaft at both ends (4 tiny bolts on each end). Unbolt the rear driveshaft at the axle end, and then pull the other end out of the x-case (have the drain-pan positioned to catch any fluid that comes out). Use that HUGE wrench or pipe wrench to take off the x-case drain bolt and drain all the ATF out of it to lighten it up for you.

Step 3:
Put the floor jack under the x-case and jack it up just enough to take any weight off the x-case (you may want to strap the x-case to the floor jack somehow). There are six bolts that hold it to the transmission- take them off. You can then pull the x-case rear-wards to disengage it from the transmission and roll it out from under the Jeep.

Step 4: Strap the NV-242 to the floor jack and line it up with the tranny. It helps to have it in 4x4 mode so you can turn the front output so the splines will line up with the input shaft sticking out of the tranny. Anyhow- bolt the x-case back onto the tranny, fill it with ATF, re-attache any wires/lines/cables/linkages that it needs, and bolt on the driveshafts (I hear that this 'case requires different driveshafts than the NP-231 you took out, look into that!)

Did I leave out anything? Oh yeah- the x-case weighs around 70#s, which means you can probably bench-press it out of and into place with the help of a friend turning the wrenches and yokes.... I manhandled an NP-208 (MUCH heavier-duty/larger version of the NP-231 [actually should be the same size as the NP-228, aka Select-Trac, used in older Cherokees...]) onto my transmission while the Jeep was overhead on a car lift. I had to do it 3 times /wwwthreads_images/icons/crazy.gif and the last time I hurt my back a little bit...so ask for some friends to help if your not a pretty buff guy.

 

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There is nothing wrong with the Selec-Trac off-road. It's actually better than the Command-Trac, due to the addition of an added range. With the ST, you get 4x FullTime (all road surfaces) 4x PartTime (loose, slippery surfaces), and 4x Low PartTime (loose, slippery surfaces at very low speeds). Whenever you are in the Part Time mode (High or Low), the front output shaft of the t-case is locked. It's the additional 4x Full Time that unlocks the front output shaft (similar to the AWD NP249 case on ZJs) that separates the two.

I would much rather have the SelecTrac NP242 and have the ability to run 4WD on all surfaces, while still having true 4wd in the woods.

My .02

85 CJ-7 258/T176/D300 Scout D44s F&R with Lock-Rites and 4.56 gears. 4" springs with lift shackles 36" SS TSL Radials Hella Rallye 4000s for guiding small planes into the woods
 

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There is another point that nobody has mentioned concerning changing a Command Trac XJ into a Select Trac one. The rear driveshafts are different. If Jeff wants to install a NP 242 in place of the NP 207, the rear driveshaft has to be changed as well. There are also 2 types of front driveshafts, as well

I agree that the 242 is a good transfer case....probably the best all around available in an XJ. Whether it is better off road than a 231 or a 207 is a subject for debate. There are a few ZJ owners on here who have reported that the 249 is a POS /wwwthreads_images/icons/smile.gif
 
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Discussion Starter · #17 ·
Ok I know some people who know more than I do that I think could give me a hand and have the tools. How much am I looking at here for the different transfer case and the rear driveshaft? Could I pick any of these up at a junkyard, or would I be better off buying them new, remember I am only 17, if it is under a few hundred overall I'm game. I'd love to give it a shot. If I can't do it which I think I could I'll just save and have someone else do it. Thanks for the info. When I get all the stuff and get ready I'll report back.

 

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At the end of my last post I did mention that the driveshafts are different. However, I don't know how they differ! Are the 242s driveshafts shorter then the 231? If so, this is a good thing as they can be shortened instead of replaced (saves money). As for getting the 242 itself, try to trade someone your 231! Maybe give them $50 cash also.... I sold my '89 Wrangler's 231 for $100, and the rear driveshaft with 2 new u-joints and a new slip-yoke for only $20, but then I'm not in this for the money....

 

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Hey Sycho, sorry your mention didn't stick in my head full o' mush; probably the start of middle age./wwwthreads_images/icons/tongue.gif/wwwthreads_images/icons/wink.gif

They differ in this manner: the Command Trac (the 86 models have the NP 207, not the 231)rear driveshaft is one piece with welded yokes at the ends and the Select Tracs have a two piece axle with center bearing and splines. Unfortunately, the Command trac shafts won't mate to the Select Trac cases (either the NP 228 or the 242). The front Select Trac drive shaft has a double cardan joint at the t'case end and the Command Trac has a CV double off set joint at the t'case end. I'm no t sure about the front shafts, though, either may mate to the 242.

I think all the NP/NV transfer cases are the same physical size so length of driveshafts are not an issue./wwwthreads_images/icons/smile.gif
 

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I never knew the NV-242 had a fixed year yoke, that is music to my ears! Now for the NP-228, I knew this used one as I had the rear driveshaft from one cut down to use in my Wrangler when I swapped the NP-208 into it....

Will the NP-228's driveshafts interchange with the NV-242s? If this is so, I know of 2-3 Jeeps (with NP-228s) in the local 'yards with this case that could be pillaged /wwwthreads_images/icons/smile.gif

I've very intersted in finding out as much about this as possible since I want to put an NV-242 into my MJ.

 
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