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Old July 1st, 2005, 16:38
chilibill chilibill is offline
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Join Date: Apr 2005
Location: Arizona
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Front Axle and Transfer Case Questions

I have a 1990 XJ with a A4W transmission and a Selec-Trac Full Time 4WD transfer case. The front axle is a Dana M30 and the rear is a Dana 35C. I never seem to hear transfer cases referred to as Selec-Trac, but rather by numbers and letters like NP 231.

I am getting ready to lift the XJ and Rubicon Express recommends a slip yoke eliminator and CV driveshaft for the NP 231 transfer case. How can I determine if my transfer case is a NP 231 and if it needs the extra components?

I have done a search for the Dana M30 axle and couldn’t find any information on it. Is it a reliable axle? Is it vacuum activated and, if so, what is the best way to eliminate the vacuum control and install something better?
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Old July 1st, 2005, 17:47
Mercenary Mercenary is offline
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Join Date: Feb 2004
Location: British Columbia
Posts: 97
Re: Front Axle and Transfer Case Questions

Hi Chilibill. It is likely you have the 242 transfer case. There is one way to eliminate wether or not you have the np 242 selec-trac transfer case is by the shift pattern. The np 242 t-case has the following shift pattern... 2 high..4wd part time..4wd full time..neutral..4wd low. The 231 doesn't have the 4wd full time selection.

Your dana 30 front axle should be vacuum actuated. The way to confirm this is to visually inspect your front axle for a box that sits on top of your axle tube with vacuum tubes running into it. Jeep changed its front axles in 92 to a full time setup. One way to eliminate your vacuum actuator is with a posi-lok. Here is the url for their web The Dana 30 is a decent axle. A friend of mine is running 33 inch boggers on his 30 right now. He is heavy on the go pedal too! I guess it all depends on what you use your rig for. He uses his mainly for mudding.

The height of your lift and your wheeling style will determine wether or not you need a slip-yoke eliminator kit with the cv driveshaft. The main problem with the slip yoke set-up on both 231's and 242's when lifting the rigs they are installed in reveals more splines on the slip yoke. The more splines exposed=less strenght. If Rubicon express is recommending a SYE, then I would guess you are lifting over 4 inches. In my opinion it is a cheap upgrade that gives great benefits.

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Old July 1st, 2005, 17:47
Gunner Gunner is offline
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Join Date: May 2005
Location: Grand Junction, Colorado
Posts: 153
Re: Front Axle and Transfer Case Questions

I'd bet money you have the NP242. And IF you have the NP242 your axle better not be vacuum actuated. If it is someone has swaped some parts. Slip yoke eliminators are always good and much stronger than stock. I got mine from Tom Woods I think it was about $300 for the kit and shaft. If you can crawl under your jeep and look at the t-case there will be a silver dollar sized plate on the drivers side that will tell you which model it is. If it's the 242 the short shaft kit is a little more work to put in due to the needle bearings on the output shaft, the 231 takes about 10 minutes. I have done them both and never even removed the t-case. My suggestion would be find out which one you have and it should be the 242 call Tom Woods and give him the scoop. He has always treated me right and never tried to BS me into something I didn't need.

As far as the axle goes. As long as it isn't vacuum actuated its pretty darn strong. Your shafts probably have the 260 ujoint which will break if your locked in the front just by putting it in drive. Otherwise your fine. They are easy to upgrade as well. I put 4340 shafts in mine an been VERY VERY hard on it. If it is vacuum actuated your still ok just a few more moving parts, and with a little work and a different seal you can put a 1 piece axle in the passenger side, you can tell if there is a "sleeve" looking part in the passenger side of the axle about mid way to the tire. . The ball joints are probably the weak link. Hope this helps

89 XJ 10" lift, 8.8 rear welded, HP dana 30 front lock right, 36" TSL's
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