lonski349

Hello everybody,

So I have a problem with my 1999 Jeep Cherokee, I have seen similar posts about similar problem but they all seem to have found a solution, none of which worked for my jeep so I am starting this page to help any others with the same problem and to help me find a solution on a page that is more focused on my topic.

Here is the problem. My Cherokee has a very loud vibration when I am driving at and above 70MPH the sound is coming from the front and is a low pitch. The pitch does not change with speed but the volume does, at around 73 the vibrations are quite and are barely notices while at 75 it is loud and sounds like the base in my car got stuck playing a loud low note. Prior to the vibration I had to replace my front pinion seal after towing a single axle trailer from Las Vegas to Flagstaff. It was after that repair that I noticed the vibrations, and just about a day later my brand new National Pinion seal broke.

To start looking for the culprit of the vibrations who also likes to destroy pinion seals we pulled the front driveshaft like many say to check the U-Joints and to our surprise they are in great condition still, so with the driveshaft out we took the Jeep for a test drive to find the vibrations were GONE!!! This lead us to believe that it is somewhere in the front end or the drive shaft. Thanks to a good friend I was able to borrow a spare drive shaft and put it in my car for testing, and the vibrations came back. So now we are just confused. So now we are just replacing and cleaning parts hoping we find the problem. So far we have rotated the tires around, checked ALL front end joints and shafts for improper movement, we have checked all front end and Tcase bearings for problems, we have replaced my driveshaft U-joints, I recently had all of my tires balanced, we also went through and checked for lose nuts and bolts. So far none of the things we have done has affected the vibration. We have no idea what to try next and if you have any idea what else could possibly be causing this issue please help us out.

Info on the Jeep:
3” lift kit (Front and Rear)(Leaf springs have a sag that has brought the back to stock height)
Stock tires
Dana 30 High Pinion in front
Chrysler 8.25 in rear

Firestorm500

Your driveshaft is bent, or unbalanced. Go to a driveline shop that can balance driveshafts. Be sure to have yours checked for excessive runout first.

When you drove your Jeep with the shaft out, it did not vibrate. Everything else is still there and turning, so it's the shaft. It destroyed your pinion seal from excessive vibrations.

By the way, you DID mark the shaft fore and aft at the U-joint attaching points before you took it out, didn't you?

If you didn't, that could also be your problem. Everything is out of phase.

I went through all of this, with both shafts, right after I purchased my daughter's '97 Grand earlier this year. 5 new HD U-joints and a new front shaft, and $700 later, it's cured.

JeepMN

Just because it's driveshaft related, doesn't mean it's the shaft itself. I would say it's just as likely to be the pinion angle as an unbalanced shaft. Of course I would have the driveshaft balanced first but if that doesn't fix it I can almost guarantee that this is your problem.

And I have never marked the shaft when changing driveshafts and have been fine- as long as everything is tightened down you should be good.

Jharris09

I had a similar issue on my 99 with 3" lift as well. I replaced the seal and the vibration started immediately after that, at highway speeds. I removed the nut and pulled the yoke out again. I used a flashlight and looked in there and the round spring thingy had moved so the yoke was smashing it. That very small difference in angle caused my vibration. May not be your problem, but doesn't hurt to check. I changed the u joints and all of that stuff which made no difference and the whole time it was just that dumb round spring.

lonski349

How could it be in my drive shaft if when I tried a different one the problem is still there

We did not mark the parts, but we did try changing the position of the pinion and it had no effect to the vibrations.

Firestorm500

How do you know the replacement shaft was good?

You seem to think towing the trailer somehow caused you to have to change the front pinion seal. Why?

I can assure you and other posters that the clocking of the driveshaft and U-joints certainly can make a difference. I have experienced that many times.

Improper installation of the front pinion shaft, as noted above, could be the whole problem. It may not be the driveshaft at all.

lonski349

The driveshaft did not needs to be a good one, if the problem was within the driveshaft the vibrations would have changed and would tell us I need a new one. Because the vibrations didn't change with the driveshaft we can say it wasn't the cause.

The pinion shaft is different on all jeeps and many people find that marking it is not necessary. We tested mine by driving it in different positions on the shaft and it had no effect to the vibrations.

At first I believed it was from towing because with the trailer on my jeep it lifted my front end up about 3" which puts a steeper angle on the pinion yolk.

XJlimitedx99

Is it possible that the culprit is improper installation of the pinion seal? If there was some play somewhere in there could it vibrate with the load of the driveshaft but not while just spinning freely with no shaft?

Just thinking out loud, I don't really know what I'm talking about

lonski349

Just an update to the situation.

We decided we had no more tests to do to the jeep so we pulled the Diff. cover off of the front drive shaft and everything was looking good till we started checking the carrier bearings. We found one of the races was able to move in its mount so we pulled the entire front axle out and took it completely apart. We found on the internals of the Diff one of the carrier bearings had gone bad and started to make the race move in its mount and one of my hub bearings was just starting to go bad.

Our plan is to replace all the bearings in the front axle and hopefully that fixes the vibration, we should have all the parts in by this weekend and should have the axle back in place this weekend. I will update you all on the problem after we test it.

If you would like to see some photos of the project I uploaded them to dropbox because they are too large to upload here.
https://www.dropbox.com/sh/afgy1b3yb...N8w54tdrqr7B3a

Jeepxj210

Check your pinion bearing or when the seal was installed the crush sleeve was over tightened thus changing the correlation of the pinion gear to the ring gear. Not saying it's the problem but it's a good place to start. It's not the driveshaft obviously and anyone that assumes that is wrong so don't listen to them.

Jeepxj210

^^^ shouldve read the last post. Nvm then that sounds like the culprit

Firestorm500

Quote: "It's not the driveshaft obviously and anyone that assumes that is wrong so don't listen to them."

Nobody was assuming anything. The diagnosis is and was a process of elimination.

Since you were a little late to the party, you have the advantage of additional information now that wasn't available when the OP first posted the thread.

That's called Monday Morning Quarterbacking. And 20/20 hindsight.

lonski349

UPDATE:

We successfully rebuilt the front axle and found many bearings in there that were at the end of their life so this rebuild was worth the tear down and the two weekends it took to complete, but the vibrations are still there and are still blowing through pinion seals.

A few other things we checked
1. Clear breather tube
2. Hub Bearings, (One was bad and was replaced during the rebuild)

We have noticed that the slip yolk on my front drive shaft has about 1/16" of lateral play. Do your jeeps have that movement?
We noticed the same movement in the replacement drive shaft we borrowed from a friend when we did the first testing.

The next steps we see to take are to find either someone who can rebuild the drive shaft or go find a new one and if that doesn't fix the problem then tear out the transfer case.

Anybody have any other ideas on the problem?
Thankfully that front axle rebuild wasn't a waste.

SteveMongr

It really sounds like the pinion angle is off. This will cause vibrations and eat pinion seals and the forward u-joint on drive-shaft.

lonski349

Take a look at the pictures of the drive shaft. There is almost no angle coming off the pinion and a very small angle off the transfer case.
https://www.dropbox.com/sh/afgy1b3yb...N8w54tdrqr7B3a