Jeep XJ Cherokee Transfer Case Interchangeability

[whiskies]

Gents.

 

Looking for a little guidance, i have a 94 Cherokee XJ with a 242J behind a AW-4 automatic on the TC tag reads

242J

5209 8046

5 19 94 2

272

 

I also have a 231J with a tag that reads

231J

5209 9212

1 14 98 3

272

 

Are they interchangeable? I have a spare front xj driveshaft and it fits both outputs, although the cases do appear to be a little different, the 231 is from a wrangler with fixed outputs front and rear, as well as having one sensor in the front case half and another sensor on the back case half. the 242J has them both together on the back half. The shift linkage looks to be the same.

The 231J has 23 spline input, not sure about the 242J as it is my daily driver, Any help would be muchly appreciated as there is so much info on the net i get it buggered up trying to get it straight

 

[Moses Ludel]

Whiskies...To sift out differences in transfer cases, splines and transfer case input hub lengths, I have furnished the two links (below) to Novak's description.  This is the most thorough and detailed account of the NP/NV231J versus NP/NV242.  You likely have a bolt-up if the input hub lengths match for your AW-4 output shaft.  (This determines engagement of splines.)  Spline count should be 23 on both units.  Seals must align at the same locations.  Novak talks about linkage to an extent.

 

Measure the input hub lengths and compare the overall lengths of each transfer case.  Length and output yoke positioning (fore and aft) will determine driveline interchangeability.  I can furnish Mopar part numbers on drivelines to clarify if necessary.  Begin by scouring these two pages at the Novak site:

 

http://www.novak-adapt.com/knowledge/np242.htm

 

http://www.novak-adapt.com/knowledge/np_nvg_input_gears.htm

 

Glad to take it from here as necessary...

 

Moses

[whiskies]

Moses;

I looked and looked at those sites, I think I may have got lucky to an extent, I believe the previous owner installed a SYE in the 231J (from wrangler) and it was getting me turned around, having said that I am going to remove the 242J this weekend and hopefully it interchanges without changing inputs, I appreciate your help, thanks

Dave     

[Moses Ludel]

Dave...So, will you be constructing a CV-driveline for the rear?  The 231J with an SYE will eliminate the slip yoke style driveshaft at the rear.  You currently have a slip yoke at the rear output of the NP242, right?

 

The common approach is to construct or buy a prebuilt rear CV driveline.  The new rear driveshaft will have a double-Cardan (CV) front joint and a common cross-type single Cardan joint for the stock rear axle U-joint flange. 

 

A CV-driveline's front joints (two U-joints with a coupler) have self-cancelling angles.  The pinion/axle end joint usually requires tilting the rear axle pinion shaft upward.  I like a 1.5-2 degree angle for the rear axle U-joint with the vehicle weighted on the ground at curb height or on axle stands.

 

If you rotate the rear axle pinion shaft upward, use steel wedge shims at the springs.  These commonly come with lift kits or can be purchased from a supplier like Specialty Products.  Make sure that the leaf spring center bolts penetrate through the steel wedges and into the axle's spring perches.

 

Moses 

[whiskies]

Moses;

 

Yes there is a slip joint on the 242, I have a front spare driveshaft with a tight double-cardan joint that I believe will work, I am only lifted about 3 - 3.5 inches and running 31inch tires. Not sure if it is the right length. I guess it will vibrate till I get the rear shims installed? Going to tackle it this weekend. I could just use an angle finder on the rear diff input yoke to find degree of angle required? I was told the 231J was from an 89 wrangler and that they are clocked differently? and it may hit the floor of the vehicle ? does that sound right to you? I thought all 231J used same case?   

[Moses Ludel]

Dave...Would be optimal of that front driveline works or is at least running long.  It can be shortened and re-balanced, that's much less expensive if the yokes will work at each end. 

 

If the shaft fits as is, vibration would not be likely if the angle of the rear single Cardan joint is within reason.  The lift is mild, and I like your idea of measuring the rear U-joint angle with an angle gauge.  It may turn out close or acceptable.  The CV joint is a big improvement.

 

This clocking issue is true, there are differences around the YJ versus XJ and BA10 versus AX15 transmissions.  Another issue is the front yoke on the NP231J from an earlier YJ Wrangler.  Compare the front driveshaft flange yoke on your NP242 to the NP231 front yoke.  The NP242 is definitely for a double-Cardan front CV driveline.  The '89 YJ could be a single Cardan (non-CV) joint with a single Cardan joint.  Compare the front output flanges.

 

You can measure the clocking by the bolt hole locations in the six-bolt flange.  The difference is around 13 degrees, readily measureable before you fiddle with the swap.  Also, YJ shift linkage may be necessary to get the 231 transfer case to work in the XJ Cherokee.  Compare the shift linkage designs and what you can do here.

 

Lastly, the early transfer case may also have a different cut on the input splines.  Note the spline count: the NP242 is 23-spline, the NP231 from an '89 model could be 21 spline or 23 spline.  If spline count matches, look closely at the cut on the splines to be sure the spline fit matches between the AX4 transmission output shaft and the earlier NP231 transfer case input.  The 1994 models were a transition in spline cut design.

 

Please share your findings.  This can be a comprehensive and valuable look at transfer case differences and what works here, Dave.

 

Moses

[whiskies]

Moses;

 

          I swapped out the T-cases today  Everything worked well, both had 23 spline count and the 231J already had a AA short shaft "fixed yoke" kit already installed, I need to order the proper gear for the speedo though as previous owner had it geared for 32" tires where as I am running 31". The rear double cardan joint shaft looks like it is stretched out to the limit which makes me a little nervous. It clocked well it all stayed above the crossmount  

          Now I have another question I hope you can help me with?

 

Here is the measurements I got using an angle meter, can you tell me what degree of shim I require? and please explain to me how you got the measurement?

Can I use the same formula for the front diff as well? I realize there is steering angles involved, I have had the front end alignment and it tracks well however not sure about the caster angle as alignment shop said it was within specs. I have adjustable lower control arms

 

[Moses Ludel]

Whiskies...First, for rear driveshaft length, you need to see if the shaft is long enough for the coupler splines to be safely engaged when the rear axle is at full drop.  (Allow for additional drop when the axle is articulated.)  A quick check without a chassis hoist would be with jack stands supporting the rear of the chassis.  Let the axle sag or hang naturally; disconnect the driveline if necessary.  The goal is to make sure that the driveshaft, if attached at full axle drop, is not hyperextending.  Spline engagement must be enough to not stress the splines or have the shaft come apart!

 

As for angles at the rear shaft joints, the CV angle is immaterial unless extreme, since one joint of the CV cancels the other joint at the CV coupler.  For the rear axle end, your concern is the pinion shaft angle.  Rolling the axle (pinion shaft) upward is to reduce the driveline slope and rear U-joint angle.  You must not raise the pinion shaft to the point that the driveshaft to pinion shaft angle becomes zero.  If you do so, the bearings in the U-joint crosses will not rotate adequately, and the joint will fail quickly. 

 

So, the goal is to get a slight angle between the driveshaft (tube section centerline) and the pinion shaft (a line extending directly from the pinion shaft).  On a lifted vehicle with a CV driveline like yours, the angle between the shaft tube and pinion shaft centerline works well around 1.5 to 2.0 degrees.  These measurements are with the vehicle's full weight at curb height, either all four wheels on the ground or the vehicle setting on four uniform height jack stands.

 

Before stressing over a slightly greater rear joint angle, consider the front axle.  Caster, as you suggest, dictates the front U-joint angle.  In some cases, the front axle's front joint angle is over 2-degrees to allow for proper caster angle.  (Caster often gets ignored on lifted vehicles to reduce the U-joint angle;  I always use the factory recommended degrees of positive caster.)

 

Note: Due to front driveshaft length and the front output yoke location on the transfer case, the front driveshaft's slope angle is typically less severe.  A Jeep CJ or Wrangler has a shorter wheelbase than an XJ Cherokee.  The CJ or Wrangler rear driveshaft is shorter.  In your case, the rear driveline is as long or perhaps even longer than the front shaft due to the longer wheelbase.

 

This factory procedure (below) for the 1994 XJ and YJ will help demystify your driveline measurements.  As noted, the axle/pinion shaft rotation is with steel tapered shims that have slots to clear the spring center bolt.  (Do you have tapered shims with the lift kit installed?)  At the correct U-joint angle setting, make sure the spring center bolt heads reach through the tapered shims (one tapered shim at each side) and seat properly in the spring perches of the axle: 

 

XJ Cherokee U-joint Angles.pdf

 

Note that if you do need to rotate the rear axle/pinion shaft upward, you will also be moving the rear U-joint yoke closer to the transfer case.  This may work to your advantage if the rear driveshaft is too short now.

 

As a footnote, you don't want a driveshaft to be too long, either.  If the splined coupler is collapsed fully at vehicle curb height, when the axle housing rises, the collapsed driveshaft has no room to shorten.  Transfer cases have been known to break apart when the collapsed driveshaft drives forward.

 

Moses

[whiskies]

Moses;

Thanks again for the info, I think turning the pinion up will allow more travel on the spline, I will print off the link next week and do some adjustments, I took it for a drive tonight and got some vibration & noise, I am going to try driving it without the front drive shaft tomorrow and try and isolate the vibration, once again thanks for the help. much appreciated.

[Moses Ludel]

whiskies...Turning the axle housing (pinion shaft) upward with tapered shims should do it.  I prefer hard steel shims.  Watch the spring center bolt heads, make sure they penetrate into the spring perches to keep the axle housing aligned. 

 

When you're done, the splined shaft of the rear driveshaft coupler should penetrate the coupler splines sufficiently and not bottom when the driveshaft collapses fully in service (must work over the full range of rear suspension travel).  Establish spline coupler travel with the vehicle at curb height and normally weighted.  Allow for proper travel when the springs drop or rise fully. 

 

Strive for the 1.5-2.0 degrees of rear U-joint angle (pinion angled slightly below the driveshaft tube line).  Vehicle should be at curb height and loaded.  This should eliminate rear driveshaft vibration with a CV driveline.

 

Keep us posted, glad the project is unfolding without fanfare.  What did you do about shift linkage?  Both inputs were 23-spline.  Were the spline cuts the same, too?  Easy fit?

 

Moses

[whiskies]

Moses;

 

I pulled the 231 tonight and re installed the 242 as I think I will rebuild the 231, it started making noises....my luck, oh well. from what I understand the spline cut difference is in the TC not the splines attaching to the trans. I think once I get the rear pinion turned up ill feel better about the cv shaft. when I get my shims I will get new center bolts as well. once I get straightened around I will post some pics of the ole girl

Dave  

[Moses Ludel]

Thanks, Dave...Sorry the older 231 unit needs attention, you're on the right track if the rebuild is not extensive.  If the fit turned out correct, your "trial fit" was worthwhile!

 

Would like to see the end result, your XJ Cherokee with a reliable, predictable part-time 4x4 system.  The 231 with Advance Adapters SYE in our XJ has over 50K miles on it, the transfer case has many original parts, with 140K-plus miles on the Jeep.  You're on the right track!

 

As a footnote, the NP231 can be upgraded to a six-pinion planetary gear set for more durability than the stock 3-pinion design.  This is a straightforward and direct conversion, and the gear set (planetary) is readily available in the aftermarket.  Something to consider during your rebuild, maybe overkill for your equipment and driving plans.

 

Moses