JeepMN

Specs: 1999 xj np242 4.5 lift with hack n tap sye. I've diagnosed my recent driveline vibration to my 242 transfer case. I've taken out both of my driveshafts and it still vibrates on both occasions, so I am fairly confident it has to be something with the 242. My only question is which bearing is most likely the cause? Front input or rear output? I can definitely hear a 'clank' in my tc if either driveshaft is spun but it's very hard to tell which side is causing the vibration. Any input? All of the 242 vibration threads have been abandoned with no answers so I'm still trying to see what my options are. Also, are both of the bearings able to be replaced with the transfercase still installed? It's my DD so I don't have a lot of time to work with. Thanks in advance.

ehall

The front output usually goes bad the first, because it gets all the crap from the drivers side tire

SteveMongr

If you suspect a fouled bearing, try using an infra-red temperature gun to confirm and pinpoint which bearing, they will usually make excessive heat.
I would not rule out other possibilities such as harmonic damper, tire/wheel issue.

JeepMN

I just got done driving around and went to feel how hot my transfercase and it was literally too hot to touch for more than a second. I am fairly certain it has to be something with the tc since I can feel the vibes and hear the binding below my feet. It's a pretty scary vibration so it's pretty easy to tell its coming from that area. Tires and wheels have also been crossed off the list as well as both of my driveshafts(had both of them rebuilt at a driveline shop)

SteveMongr

As for TC temperature, 150 F is normal. Anything over 120 will be too hot to touch. IR temp gun is $20. Works great for diagnosing wheel bearings, sticking brakes, cooling system function, dash gauge comparison, etc.

JeepMN

Well, just went and got an IR gun and most of the case was around 150*.

I've literally replaced ever single u joint and wheel bearing within the past year. Gears only have about 25k miles on them and there doesn't seem to be much play in any of the yokes, transfercase included.

What do you think?

JeepMN

Quick question. If it was the front input bearing that was bad and I took my front driveshaft out, could it still cause my vibration? I'm guessing the front bearing still spins even though I only have the rear driveshaft in. I have never taken apart a transfer case so I don't know too much.

SteveMongr

There are other things to rule out before tearing apart TC.
Vibrations can be tricky. You use the term 'binding' and 'clank in the transfer case', hard to figure from this side of a computer.
Suspect motor mounts, muffler where it passes over cross member, flex plate.

SteveMongr

No, front output shaft on TC will not spin.
If you suspect a specific output bearing, that yoke would show high temps and the IR gun can pinpoint heat spikes.

ehall

In 2WD the chain that drives the front output is disconnected internally, so the front output will only turn if the driveshaft turns it (which is what normally happens). If you disconnect the driveshaft, in 2WD, the front output should not turn much, although it can get some drag from the bearings.

In 4WD Part-Time the chain is locked and both outputs spin at the same rate, regardless of the driveshaft.

In AWD Full-Time the chain is engaged on the differential and power will go to the output with the least resistance. If the front driveshaft is disconnected, the front output will have no resistance and all the power will go there (car won't move)

JeepMN

Thank you for the information. That explained it very well. So with my case, the symptoms while in 2WD are much worse(with both driveshafts in) the vibration is terrible and makes me want to throw stuff at the jeep. While in Full Time, the vibration is muchhh less but still noticeable. While I drive without my rear driveshaft in, while in part time my vibration is much less but you can feel a pulsation while coasting. When it's under load it's not very noticeable at all. So with those symptoms where would you go? Remember I have 2 rebuild driveshafts, pinion bearings on both differentials seem fine(I replaced my rear pinion seal and my timken bearings looked and felt/spun fine)I was able to move the actual pinion gear in and out quite a bit with the seal removed but idk if that is normal or not.

JeepMN

Wheels and tires have been checked off list and I have replaced all wheel bearings in the past year. It is definitely something with driveshafts. If you were in my jeep you could definitely tell it was something under your feet.

ehall

Is the Jeep lifted?

JeepMN

Yes around 4-4.5'' with a hack n tap sye. I am confident my pinion angles are correct since I didn't have this vibration 2 months ago with the same lift.

ehall

With the driveshafts installed, grab the slip joint with your hand and try to shake the joint. Does it have any play at the joint?