JP Magazine Homepage

Tech Questions - January 2008 Your Jeep


By Christian Hazel
photographer: Christian Hazel


The Wheel Deal

I own a '95 Wrangler and am about to have a Rough Country 4-inch lift installed. I plan to buy some new wheels and tires, but before I do, I want the right size. I will be buying 33x12.50-15 tires, so do I need 15x8- or 15x10-inch wheels? I drive my Jeep every day and will do limited off-roading.

C.L. Long
Teague, Texas

I ran 33x12.50-15s on my '95 YJ on 15x8s with a 4-inch lift. I had a little rubbing of the front tires on the springs at full turn, and I needed to nip just a tiny bit of plastic from the rear of the back fender flares. Otherwise, they were a good fit. I think you'll have more clearance issues than this with the wider 15x10s. My advice would be go for the 15x8s.

Shudder Bugger

I believe the time has come to rebuild my NP231. I have a '95 ZJ with a 4-inch Rock Krawler lift and a 1-inch T-case drop kit that I swapped the NP231 into. I've been experiencing some bad vibrations, especially at highway speeds, and I have deduced that it's the T-case causing the problem

I removed the front driveshaft the other day to see if that was the issue, and it seemed to be. I took my ZJ on the highway all the way up to 85 mph and didn't feel a single vibration. I thought it was the driveshaft's balance. I took it to a very reputable shop that built it for me, and the guy there said it was probably out of balance due to the rub mark on the tubing (from my crossmember when I didn't have the T-case drop kit installed). He put it on the machine and informed me that it was, indeed, out of balance. He balanced it, and I reinstalled it under my ZJ. The vibration was still as bad as it was before. This tells me that it's not the tires being out of balance nor is it anything in my frontend, and it ultimately was not the driveshaft.

I put it up on an alignment rack at work and jacked it up by the axles. I put it in 4-High, so the front driveshaft would be spinning as if I were going down the road and accelerated to about 70 mph. A few technicians said my T-case was pretty noisy and felt like it was shuddering a bit.

Now, a few questions for you:
1) What does this sound like to you?
2) Should I go ahead and get a complete rebuild kit for it?
3) Since I'm already going to be tearing into it with the rebuild kit, should I upgrade components like the kits offered by Tri-County Gear?
4) Should I just go ahead and do a slip-yoke eliminator and get a CV rear shaft because the only way to upgrade components in that way is with a short-shaft conversion through Tri-County Gear?
5) If I get the slip-yoke eliminator and take the T-case drop kit out, how do I keep the front driveshaft from rubbing the crossmember when the axle is at full droop?

Mike Kline
Charleston, South Carolina

From what you're saying, it sounds like the vibration came on at the same time you installed the T-case drop. I'm thinking your vibration is caused by less than ideal front driveshaft angles and not by any problem with your T-case.

When you lower the rear yoke of the T-case for a better rear driveshaft angle, you raise the front yoke, which worsens the angle. Since your ZJ has no front hubs, your front driveshaft angle affects vibration just as much as the rear because it's always spinning. A 4-inch lift on these trucks is a lot and is just marginal for the front driveshaft angle. Dropping the case or adding 1-inch lift motor mounts could be just the thing that would push the front driveshaft angle over the top and make it start buzzing.

First, you can add locking hubs to your front Dana 30 with a kit from Warn. Sorry, I know it's pricey, but that's pretty much the only way you're going to keep that front driveshaft from spinning in 2WD.

Second, you can install adjustable control arms or cam bushings on the lower control-arm mounts at the axle to rotate the front pinion up to alleviate the driveline vibration. However, this will reduce caster and can lead to some wandering.


1  | 2  | Next
Get no-obligation new car and truck invoice pricing quote online.

Related Photos

Related Articles

 
 
 
Ask Bree Three - May 2007
Bree answers the age old question... Why do Men have nipples?... more
 
Ask Bree Three - March 2007 - Jeeps, Off Road, & Pictures
What if Chuck Norris drove a Civic on Star Trec?... more

Jeep Forums

 
Hood Louvers
I am looking for hood louvers to get / let the heat out. We have had some hot days here lately,... more
 
3.0L CRD and BIODIESEL
Hello All! I'm brand new to this forum and am glad to have found you. :cool: I'm an avid... more
 
Stolen 1994 Jeep Cherokee Sport 2 Door 2WD RED
VIN #1J4FT67S0RL234589 IL Plate C650246 Has a dented panel under the gas tank door. Also had a... more
 
Suspension?? and recommendations???
Hello, Im looking to put 35 inch tires in my jeep and was trying to figure out whether to go with... more

Jeep Blogs

 
Waking the Neighbors
It's been a while since I plugged in. I think I'll lay down my acoustic and wake the neighbors. ... more
 
Robot Mule
A co-worker e-mailed me the link to this mechanical robotic mule site. C LICK HERE Pretty creepy. ... more
 
Computer Rebellion
It is now almost midnight. I did no real work today, I just fought my two computers (work... more
 
Crappy Birthday Bosch ABS
Maybe today I'm a more cynical ass than usual. ... more