NP242 Lovers with Lifts

I've got a 91 XJ / Jasper NP242 with SYE, D30 / D44 at 3" and planning to go to 4.5"

The RE site says "Over 3.5-inches of lift on a full-time NP242 unit may cause unacceptable vibrations on the front driveshaft, when driven in ”part-time” or locked constant use 4WD."

After searching forever, setting caster at 5.5 (from GoJeep's site) seems a good place to start. And rebuilding the front shaft would be a good idea considering mileage.

Going with RE drop brackets, adjustable upper and lower control arms so pinion / caster changes won't be that difficult. If necessary, I can add a T-case drop (not something I'm keen on).

I know there are a few people out there running an NP242 on a lifted Jeep that have addressed vibrations on the front driveshaft. . .

I'm good at 4.75" of lift, with my 242, adding a t/c drop will make the front shaft angle worse causing more vibes. I went with adjustable upper and lower arms and had my buddy at the alignment shop sent up my front end including pinion angle

I'm at a bit less than 4.5 inches, but have had no problems (80 is about as fast as I've had it, post lift in 2WD--about 65-70 in Full Time, probably). I did have DW at 60+ until we moved the caster down to about 5* via the LCAs. That was prior to installing the stabilizer as I wanted it right without that potential band-aid.

I do have the Tom Woods installed H&T and new TW HD axles front and rear. No xfer case drop.

my 91 on it's first lift was at just under 4.5 without even the sye on the 242 and i never had vibrations or odd steering issuses. when i went up to 5.5 i still had no vibes but i noticed when i was regearing that at full droop with both tires hanging the u-joints were locked on the rear shaft. not a problem when i was crossed up on the trail but it would have shredded over the first whoop-dee-doo in the desert.so i installed the tom woods sye. at that time i was about 6" lift, re drop brackets,fixed lowers, adj upers set all the way in,double shims in the lca pockets and still had no vibes. the earlier xj's seem to behave better with lifts than the later ones. i really don't think you need to case drop too. all you will get worse front angle (since you should have a hp axel) and less clearance on the trail...

I have a 6.5 on mine with t-case drop.. (3/4) drop... No vibs

242 w/ a Tom Woods SYE and 6.5" Clayton's Hardarm. Mild vibes at highway speeds, (60-70 mph) but it's a very mild, slow rhythmic hum, not an actual vibe per se. It's acceptable to me, given the mods. I did set the front pinion angle (87 degrees measured up/down across the front of the diff cover face)


No T-case drop, not really possible with the Clayton's kit.

242 RC 4.5" no sye..... no vibes, no noises.. only issue is i need my front end allighned cause it steers to the right a bit..
I love driving in FT.

242 RE 3.5 actual lift ~ 5", TC Drop (for the rear not front), SYE sitting in a box waiting to be installed..

I don't mean to hijack the thread, but I have a question that this topic brings to mind. Since we are talking about setting the caster to 5-5.5 does that mean you NEED to have adjustable LCA's and UCA's. When I was going to have a shop do my front half of the lift and do an alignment, they said "unless the LCA's are adjustable you are just wasting your money- there is nothing to adjust" I thought that was strange and decided to walk away. I do not however have a working knowledge of caster/camber, etc. I have been told with fixed LCA's for a 4.5 lift and stock UCA's I will be fine. Is this correct? If anyone can PM me with sound advice I would greatly appreciate it. :wave1:
BTW- 4.0, AW4, NP242 going to RC 4.5 Rear leafs, Rusty's 4.5 front Springs. The only concern is about fixed uppers and lowers. I do not have a hack and tap or TC drop planned.

With that height, you might find yourself opting for one or the other (drop or H&T) To make this as short as possible (I'll just say I'm the exception to everyone else in this thread having vibe free lifts) I have 3.5 RE SF with fixed lowers, RE H&T with front shaft in rear....I DO have vibes, minor from the front shaft. And have had them from the day I did the lift (put the H&T on thinking it was my rear causing it when in fact it was more likely the front) I just got my RE adjustable upper CA's in the mail yesterday, so HOPEFULLY that will allow me to bring my pinion up enough to stop the vibrations....

As far as caster...it IS adjustable VIA the LCA's if you look at them there are slotted bolt holes at the rear frame bolt, that moved in and out by using shims behind the arm, adjusts the length of the arm, and changes the caster. But the problem with mine was, even with the LCA as far back as it goes, my pinion is still not set at the right angle to eliminate vibes....= needing longer uppers to correct it (or shorter lowers...)

With aftermarket LCAs and stock uppers, I see a LOT of people having no problem. I did, so just depends whether or not your jeep likes you taking it apart or not

91Woody said:

I don't mean to hijack the thread, but I have a question that this topic brings to mind. Since we are talking about setting the caster to 5-5.5 does that mean you NEED to have adjustable LCA's and UCA's. When I was going to have a shop do my front half of the lift and do an alignment, they said "unless the LCA's are adjustable you are just wasting your money- there is nothing to adjust" I thought that was strange and decided to walk away. I do not however have a working knowledge of caster/camber, etc. I have been told with fixed LCA's for a 4.5 lift and stock UCA's I will be fine. Is this correct? If anyone can PM me with sound advice I would greatly appreciate it. :wave1:
BTW- 4.0, AW4, NP242 going to RC 4.5 Rear leafs, Rusty's 4.5 front Springs. The only concern is about fixed uppers and lowers. I do not have a hack and tap or TC drop planned.

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How to adjust your caster here:
http://www.go.jeep-xj.info/HowtoAlignment.htm
Yoke style SYE using front shaft IF you have a auto AND a D44 or 8.25:
http://www.go.jeep-xj.info/HowtoSYEconversion.htm

Backroads said:

With aftermarket LCAs and stock uppers, I see a LOT of people having no problem. I did, so just depends whether or not your jeep likes you taking it apart or not

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I think my Jeep get's lonely if I don't take it apart at least once a month....there is always something to replace- which usually gets upgraded at the same time, but wow....I don't think it will ever let me stop operating.

Thanks Gojeep for the links!

I have the RE 5.5" with drop brackets. 242 w/RE hack and tap. I installed the lift myself before I really knew about shimming and pinion angles. Maybe I am one of the lucky ones, but I have no vibes at all.

I did, however, drive around a parking lot post lift/pre SYE and had a harsh vibe from the rear. After the H&T install it was back to normal.

8" Clayton lift, hp30 with 242+Tom Woods SYE always used on the street in fulltime. No vibes in last 10,000 miles. I have run it in 2wd with my Warn hubs unlocked a couple of times and it sounds the same.

fubar XJ said:

242 w/ a Tom Woods SYE and 6.5" Clayton's Hardarm. Mild vibes at highway speeds, (60-70 mph) but it's a very mild, slow rhythmic hum, not an actual vibe per se. It's acceptable to me, given the mods. I did set the front pinion angle (87 degrees measured up/down across the front of the diff cover face)


No T-case drop, not really possible with the Clayton's kit.

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Using the formula off GoJeeps site, that puts Caster at 6 degree's, wonder if dialing it to 5 or so would eliminate the vibe?

I get the point about the T-case drop and the front DS angles. . .