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NV241 Rock Trac Transfer Case Swap

Discussion in 'TJ How-to Guides' started by Rook, Dec 20, 2016.

  1. Rook

    Rook Member
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    Im not very good at explaining how I do things, so I will try and give you guys the basics thta was done to make this install complete.

    1st off let me tell you the only thing that will bolt/plug right in, is the tranny and vent hose. I believe just for a 97-98 TJ jeep wrangler. Before I started my install I tried to get all my parts needed so I wouldnt be running around at the last minute. The NV241OR Rubicon transfer casecomes with 32 spline output shafts, on the front come with a 1330 cv yoke and the rear comes with a flange.

    T-case003.jpg

    With the help from Coast Driveline in Ventura Ca. I was able to score 2, 1310 style yokes that will bolt right up to my current driveshafts.

    T-case005.jpg
    1310 on left 1330 on right

    I also noticed that the speedo gear and wiring was different from my NP231. The 231 has an actual gear, and the Rubicon transfer case comes with a magnetic speedo sensor. The new wiring does not plug right into the harness. Along with this, I knew the 4x4 light would also not work.

    I did the wiring last, but I went to a local auto parts store and picked up a 3-wire connector that is weather resistant. One huge thing that helped out was a wiring diagram I got from TeraFlex. There SYE kit gives you the cennector you need and has a wire diagram chart for what color wire does what. The place I got the info has not been working since I used it, but ill give the color combos later.

    So basically I thought I would have the most trouble with wiring and maybe some shift linkage stuff. It turns out that the Transmission mount will not clear the new and much larger NV241OR. I was kind of stumped at this point and actually got an used Rubicon skid plate to see if that would work. I soon found out the frame bolts would not line up right. I ended up buying new Grade 8 bolts for the mount and made about a one inch spacer

    T-case024.jpg

    this is the gap, because it hits on the lower pic

    T-case022.jpg

    so an easy fix(I know its not the best solution but it has been very solid so far and most of the weight is on the skid plate anyway)
    T-case028.jpg


    so now that I had the mount figured out, the size of the new case is not supposed to be used with the older style skid from 97-98. The newer cross member skid plates are much larger and have plenty of room for the Rock-Trac t-case. In order to make all the geometry in the shift linkage the same, and not have the case hitting the tub, I HAD to either put a body lift or a t-case drop.
    this angle has to be even or links will rub

    I just so happen to have my old (but brand new) 1 inch lowering kit. This works perfect, but I really dont like losing another inch of clearance so will probably be doing a body lift later on towards summer.

    T-case026.jpg

    T-case025.jpg

    T-case031.jpg
    One thing that really confused me was the shift pattern on the two cases. ON THE ACTUAL CASE they shift differtly. Its hard to explain unless you are looking at it in front of you.

    Basically the rod im holding PUSHES down on the lever on the case(green spot), pushes down to get to 4LO. and the Rubicon transfer case it actually shifts upwards towards the tub of the vehicle.

    T-case011.jpg

    you can see the different positions of the lever when they are both in 4low here:

    T-case014.jpg

    hopefully I am making sense when im showing these pictures, trust me this was a BIG project and there were tiems where I didnt think I would be able to pull it off, doing 95% of the work by myself and the Rubi case is NOT very light weight.

    So along with my troubles with the shift linkage you CAN re-use old stuff. You can buy a new bracket from Skyjacker or Novak adapters but I was in a time constraint. The rod that goes from the shift handle(inside the cab) to the lever on the case has to be shortened a little less than an inch. I bought some small tubing and was going to cutt and sleev it to the size I need. Just to see if it would work, I just bent the rod. Luckily enough it works fine(for now).

    T-case027.jpg
    so i just left it for now.
    these are the 3-wire plugs I got:
    wol_error.gif This image has been resized. Click this bar to view the full image.
    T-case010.jpg
    wol_error.gif This image has been resized. Click this bar to view the full image.
    T-case029.jpg

    Im sure I left out a lot, but if anyone has any questions feel free to ask!!! I searched everywhere and got very little feedback so basically had to figuer it out as I went. Everything is solid and works great. I have not had any "real" testing done with the new 4:1 but from the my experiences on going through the neighors empty lot and short wall in front of our house all I can say is.....wow...Johnsone valley here I come..again! On the street in 4LO i slammed on my brakes and could not stop my jeep or stall it. I cant wait to get it out on some rocks. Well here are some more random pics! hope you enjoy!

    T-case015.jpg

    T-case001.jpg
     
  2. Kyle_W

    Kyle_W Artist formerly known as "Nashorn101".
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    I am not sure why when you switch to 4-lo, why you move so much slower than when you are just in 2wd?

    I understand that you basically drop to a lower gear, but I just don't understand that? What gear are you dropping to - does your transfer case have a separate gear only for 4-lo? (I imagine that 4-hi uses the same gear as normal 2wd)

    And, if I understand correctly, the change out that you just did gave you an even LOWER idle speed while in 4-lo?
     
  3. Chris

    Chris Administrator
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    Read this: How a transfer case works

    Correct! Great for rock crawling or other slow crawl terrain.
     
  4. Kyle_W

    Kyle_W Artist formerly known as "Nashorn101".
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    Thanks!
     
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  5. mrblaine

    mrblaine TJ Guru
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    Rook, a few things for you. First is your trans mount. You will ruin your transmission if you don't get the bolts tightened up against it. Get a bolt long enough that you can see the threads on top. Put two nuts on where you have one. Thread one nut up against the bottom of the trans and tighten it down so the soft cast aluminum isn't getting the threads hammered by the bolts. Thread the other one down against your plate like you have it now and tighten it. That will stop any damage that is going to happen.

    Standard makes a switch that screws in there where the big one is now. It works opposite of the one in the 231 that closes a circuit to turn on the 4wd light so you dash light will work.

    The 241 does shift backwards which is why the lever points up instead of down like the 231.

    The shift linkage is very different and if you need some 241 specific, I probably have several. I would convert to a cable shifter if it was mine.

    I would have also kept the balancer on the back of the case. I've had several conversations with Tom Wood about that and he strongly recommends it due to some funky harmonics the 241 develops with the right gearing combos.

    Not sure why you couldn't find any write-ups on the swap, I've seen several over the years.

    The connector for the t-case switch from Standard has a keyed slot that you will need to cut into your harness side connector.
     
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  6. Chris

    Chris Administrator
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    BTW @mrblaine, I see the Rubicon transfer case called the following names:

    NV241
    NV241OR
    NP241
    NP241OR
    NP241J

    I'm a little confused. Do you know what the proper name for it is?
     
  7. Stinger

    Stinger TJ Addict
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    :wave1:
    The build sheet on my 05 callers it a NP 241 OR.
    A Google search shows an 03 as NP 241 but the post title says NVG241 OR Rock Trac.:wave1:
     
  8. Chris

    Chris Administrator
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    Haha... Yep, I've seen it called so many things that it confuses me. I've always called it the NP241OR.
     
  9. mrblaine

    mrblaine TJ Guru
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    It has to the with the progression of the company and the various names associated with it over the years.

    New Process = NP
    New Process Gear = NPG
    which morphed into New Venture Gear where we get NVG which is often shortened to NV.

    This will help and it also has the full correct name for the t-case in the Rubi.

    http://www.allpar.com/mopar/transmissions/NVG-history.html

    The 231's still have NP231 on the tags. I'll have to check the tag on the Rubi case I have and see what it says.
     
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  10. mrblaine

    mrblaine TJ Guru
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    All are technically correct.
     
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  11. Stinger

    Stinger TJ Addict
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    I just call it a 241!
    What I called it when mine blew up and cause over 5k in damage isn't printable. For just a bit more one can install an Atlas and be done with it.
     
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  12. Teagan

    Teagan New Member

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    Hi Rook,

    I am picking up a rubi T-case tommorow and am doing the swap into my 98 tj. If you dont mind, I have a few questions for you. So the only parts you had to buy were the yokes? And to fix the spedometer you just spliced the wires together with a connector? Other than that it bolted in fine after u did a t-case drop and made custome mounts? The 4wd spedometer works fine now and the 4WD light come on?
     
  13. JeepDew

    JeepDew New Member

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    @Teagan, did you ever do the swap...I'm so close to pulling the trigger on this because it looks more complicated to me than what I thought it would be.... Keep me posted if you don't mine.

    Thank you in advance.
    JeepDew
     
  14. ac_

    ac_ TJ Enthusiast
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    It does look like a lot of hurdles to overcome. What is the reason for the swap? I mean what do you gain by having a Rubicon transfer case?
     
  15. Chris

    Chris Administrator
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    I'd just put in an Atlas transfer case if I didn't already have a Rubicon. It would be a hell of a lot easier I think.
     
  16. Ranger_b0b

    Ranger_b0b TJ Addict

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    4:1 gear ratio in low is the main benefit. It's pretty awesome...
     
  17. mrblaine

    mrblaine TJ Guru
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    Not even close. By the time you get through lining up either the shift levers or installing the cable shifter box and getting them to work in the OEM slot in the console, you could install a 241 and be done. That and the tub work for an Atlas in most raised skid configurations is a fair bit more time consuming. Plus you need a custom mount in most cases. The Atlas is a viable albeit dumb option. It is big, heavy, and way too tough for anything we need a t-case for. I run one but I'm sure not happy about it.
     
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  18. ac_

    ac_ TJ Enthusiast
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    Thanks for that,
     

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