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Drive Line Vibrations??

mfascuba

NAXJA Forum User
OK, here goes. The jeep is a 1997 XJ, 4.0 automatic, NP242 xfer case with a 2" budget boost (coil spacers up front, shackles and 1/2" spacers in the rear), on 31" tires.

When I first put it on the road after lifting and "freshening up" the suspension (new upper & lower control arms/bushings, all U-joints replaced, end unit bearings replaced), there was a lot of "road noise", but it was just loud. I started getting some clunking in the front end so I took it to a shop that does quite a bit of jeep work and had the front and rear diffs checked out, and seals replaced. They also did the front & rear pinion bearings, and rear carrier bearings. Apparently the previous owner had grenaded the D35 rear somewhere along the way and had it rebuilt but the shop had left metal shavings in the axle tubes that were gradually taking their toll. Anyway, I picked it up late last week without the front driveshaft, as they were keeping that to put a new cardan joint on it, so I've been 2wd by default since then.

Before on the highway the jeep was just loud from road noise, now it has vibrations that kick in around 65 mph and continue/get worse up to the 85 mph range where I stopped accellerating.

When I did the U-joints in the front axle I also did the rear drive shaft u-joints (and tried the front DS joints).

The rear axle is much tighter (less lash) than before, as it doesn't clunk when I put it in gear (NICE!!). The rear end almost feels like a tire out of balance, but the weights are all in place and they ran smooth before the axle work. The shop said my planetary gears in the front of the transfer case were very worn and causing what I'd categorized as road noise, and after his explaination it made sense.


Anyway, am I now at the point where my rear axle has been refreshed to the point where my driveshaft needs to be replaced? If so, I'm thinking of doing a SYE kit (hack-n-tap) on a remanufactured transfer case, all at once.

Am I barking up the right tree, or am I just confused?

Thanks,

Mark
 
The real source of my confusion was that everything was OK until I tightened up the rear diff. Is there any logic to that? I'm baffled. Before, I could hit 90 on the highway, no vibes, now a week later, 80 and I'm really getting worried....

Thanks,

Mark
 
How do they know your planetaries are bad without taking the case apart?
Just by test driving it?
The planetaries only come into play when you have it in 4wheel low.....not in 2wd.:doh:
That's how you get the low range reduction.....

EDIT:You have the 242 case...but still.In 2wheel hi the planetaries aren't involved.
 
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To add to this post...I'd think twice about the hack-n-tap. For like $450 you can do a short shaft AND custom drive shaft from Tom Woods. Unless you're very confident in your fab skills, I'd avoid the H/C. First you need to remove the output shaft to cut it...same to install a "new" short shaft. Second, after hacking the shaft, you need need a new drive shaft...Tom Woods is second to none!

Just my 2-cents...I'm installing a Tom Woods short shaft and custon drive shaft now in my 242.
 
It can be done without out removing the output shaft....many have done it that way.Put the tranny in neutral and let the engine idle(which turns the output shaft slowly)and use masking tape to mark the cut all the way around.Fire up the angle grinder and hold it steady.:yelclap:
 
:spin1: Gojeep the Aussie dressed a shaft someone had done a bad hack job on by putting it in reverse with the engine running, said it worked great![read it here of course] That gives me the confidence to do my own when the time comes. I have a 242 so I'm going to do the Corvette slip yoke/frnt d/shaft thing.
 
Where I'm probably headed is to order a remanufactured case and a tom woods shaft, fit the modified shaft into the case before installing it and calling it a day. I've spent more than I'll admit on this particular vehicle, but the end product is worth it - a "real" 4wd vehicle that doesn't shake, rattle or die, and I can drive it to work every day and off road to dive sites on the weekends.

Mark
 
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