Jump to content

Recommended Posts

Since the MJ has started pulling daily duty, a lot of issues have begun to rear their ugly heads.  The most concerning at this point is a heavy vibration I'm getting under load. Like if you lug the motor. Cruising in any gear at any speed, I'm getting heavy heavy vibrations while accelerating but if I let off the gas and coast it immediately goes away. 

 

I have a few ideas but wanted to hear what y'all had to say before I dug into it. With a 1.5 hr commute each way, I don't have a lot of time to diagnose so I'm looking to nip this in the bud ASAP the first time.

 

Thanks!

 

'92. AX-15, 4.0L, 4x4

Link to post
Share on other sites
13 minutes ago, 89 MJ said:

Maybe check your motor and transmission mounts.

Those are fairly new (replaced 3-ish years ago...only 2-4,000 miles on them since). I will check tightness though.

Link to post
Share on other sites

Crawled under the truck yesterday and looked around/felt around/pried on stuff with a big ol' screwdriver. Rear end seems to have some slop in it, I'm able to get a good 10-15 deg of rotation on the driveshaft while tranny is in neutral and rear wheels are chocked.  Front was actually a little worse. What confuses me is that the vibration completely goes away at any speed if I let off the gas or press in the clutch. U-joints themselves were all replaced about 3000 miles ago (tranny swap to external slave) and don't seem to have any play in them from what I could see.

 

As far as trouble shooting, I'm thinking pull the front driveshaft and test drive. If it's still there, put the front back in and pull the rear. Test again. If it's a driveshaft u-joint that should reveal it. If it's something else, I'll go from there.

 

Thoughts?

Link to post
Share on other sites
On 10/13/2020 at 10:11 AM, rokinn said:

First question would be where does the vibration seem to originate?  First thought was drive shaft U joints.  Or front axle U joints.

It seems to be coming from the engine compartment but it's difficult to say for sure. I replaced the harmonic balancer just to be safe initially (mine was getting up there in age and the rubber was in bad shape). So front u-joints could very well be it but I will say it's been very difficult to pinpoint where it's coming from. I've been chasing a bad wheel bearing-esque noise for the past 1000 miles on this thing and having a camper shell makes everything seem to resonate and it's difficult to track down where the noise is coming from.

 

On 10/13/2020 at 8:42 PM, Wounded_Fighter said:

My buddys MJ had a similar issue mostly under gear 2or higher and real bad in a turn.

driveshaft had slop...

This happened...imagejpeg_0.jpg.beb8030fd767a7aacab60e94ce6c4138.jpg

 

Apparently he still covered 200 miles like this... without knowing...

Holy............:sad2:

Link to post
Share on other sites
On 10/16/2020 at 1:55 AM, MiNi Beast said:

I'm thinking bent fingers on pressure plate. or pilot bearing. how in depth was your clutch repairs? 

Brand new clutch when I did the external slave swap. New clutch pad, pressure plate, bearing the whole 9 yards. Been in for 3000-ish miles and hadn't vibrated like this until last week.

Link to post
Share on other sites
On 10/15/2020 at 5:47 PM, omega_rugal said:

 

wihtout the engine pushing, the joint is free to rotate


Yup, got that. In my experience U-joint vibrations are dependent on vehicle speed not engine RPM and usually still vibrate unloaded. This one completely disappears. Will continue to troubleshoot this week....

Link to post
Share on other sites
3 hours ago, 89 MJ said:

Does the truck seem down on power compared to before the vibration started? When my truck misses, it seems to shake a little bit.

Nope not at all. Doesn't strike me as an engine miss, and I can't get it to replicate very well in 1st/2nd gear (where a miss would be most obvious).

Link to post
Share on other sites
3 hours ago, Pete M said:

I had a rear ujoint go bad in my Liberty that gave vibrations under load, but went away if I coasted.

This is what I'm leaning towards right now. As soon as I can get some time alone with the Jeep, I'll be pulling each driveshaft and driving to test. I'm hoping for a driveshaft ujoint and not a front axle ujoint.

Link to post
Share on other sites
This is what I'm leaning towards right now. As soon as I can get some time alone with the Jeep, I'll be pulling each driveshaft and driving to test. I'm hoping for a driveshaft ujoint and not a front axle ujoint.

I don’t know if you have a SYE but if you remove the rear shaft and drive the tcase will puke out the rear output shaft. Just a heads up


Sent from my iPhone using Tapatalk
Link to post
Share on other sites
4 hours ago, blakews2217 said:


I don’t know if you have a SYE but if you remove the rear shaft and drive the tcase will puke out the rear output shaft. Just a heads up


Sent from my iPhone using Tapatalk

Yeah was wondering about this. Don't have an SYE. Wouldn't be driving very far and there's no hills in south Louisiana....I think I'll be ok. Anybody done this before? 

Link to post
Share on other sites
6 hours ago, Tex06 said:

Yeah was wondering about this. Don't have an SYE. Wouldn't be driving very far and there's no hills in south Louisiana....I think I'll be ok. Anybody done this before? 

 

It will still leak some because of the downward lean towards the back end. With driving it will spin the fluid also so you'll have the lovely "leak line" on the under carriage too.

 

"Some" fluid. Very relatively. If its a lot. You may hear new noises from transmission. 😆

Link to post
Share on other sites
1 hour ago, Wounded_Fighter said:

 

It will still leak some because of the downward lean towards the back end. With driving it will spin the fluid also so you'll have the lovely "leak line" on the under carriage too.

 

"Some" fluid. Very relatively. If its a lot. You may hear new noises from transmission. 😆


Just put in the slip yoke at the very least. The tcase will pump oil out of the rear output of nothing is there

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...