• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Vibration and noise diagnosis

brielly

NAXJA Forum User
Location
nj
My 2001 cherokee, with no lift lift vibrates horribly when accelerating on the highway 65 mph and over. I also get a rumble/clunk when I let off the gas and get back on it at that speed. If I just keep my foot lightly on the gas the noise will stay until I press more or let go.

So far Ive had the rear driveshaft u-joints replaced with spicers and the shaft balanced. The front driveshaft is out. Tranny and motor mounts are new. I also have an issue with my rims being slightly bent causing a vibe at 55. The rims are being replaced in the next few days but I dont think they are the problem since the main vibe is during acceleration.

Any ideas on what to do next? Its getting to where I don't want to drive on the highway anymore.
 
Last edited:
U-joints are always the first suspect. You have that covered. Pinion bearings are after that. The bent rim or rims would be next.
 
I also get a rumble/clunk when I let off the gas and get back on it at that speed.
That's classic pinion bearing preload too low. Could be that way for many reasons. Check your pinion nut at the yoke to make sure it's not loose. But, even it if is, you really need to pull the carrier to tighten it down properly (can't measure preload with the carrier in) so I would check the bearings and races while it's out anyway.
Check the u-joints first since it's way less work, but I doubt that's the major problem here.
 
I would suspect the tires and then the pinion preload.

Since you have a 2001, do you have ABS and what kind of rear axle do you have? 35 or 8.25?
 
Rear axle is the 8.25, no abs. No issues with exhaust hitting the crossmember. If it's the pinion preload, what kind if repair/expense am I looking at?
 
Depends on the damage. I'd be worried about just tightening up the nut to crush the sleeve a bit more to get the preload without looking at the bearings on a used gear set. So, your looking at the work required to reset gears if you're lucky and the bearings and races are good. Otherwise, you're looking at new bearings and such if they are bad. Not an easy job like an oil change and you'd need some special tools and a lot of patience.
 
Out here we can buy complete axles for $100 pretty much all day long so we generally replace the axle. For repairs, expect shops to charge $400-800. Ask around in your local chapter. Another alternative in a stock vehicle is to get a Dana 35 if you can't find a 8.25. You would need the driveshaft and new u-bolts because 8.25 driveshaft is shorter and the tubes are wider. Out here D35 are essentially scrap metal, often available free up to $50.

To further isolate the problem, you can jack up the rear, take the tires off, and brake drums, and disconnect the driveshaft. Then turn the pinion yoke by hand. It should be smooth. If its rough, or can be moved up and down or in and out, that's your problem.
 
Just an opinion but before you get to far into things check the rear axle U bolts and the front control arm bushings.

I've had rear differential U bolts stretch and loosen. If differential rocks inside the U bolts it can make for some strange U joint angles.

I usually block the tires and parking brake, then have a buddy push/rock the body front to rear.

I also wonder about the flex plate?
 
thanks, u bolts were new last year along with new rear springs. I'll check the other items over the weekend.
 
Back
Top