Tex06 Posted October 13, 2020 Share Posted October 13, 2020 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 comment Share on other sites More sharing options...
89 MJ Posted October 13, 2020 Share Posted October 13, 2020 Maybe check your motor and transmission mounts. Link to comment Share on other sites More sharing options...
Tex06 Posted October 13, 2020 Author Share Posted October 13, 2020 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 comment Share on other sites More sharing options...
rokinn Posted October 13, 2020 Share Posted October 13, 2020 First question would be where does the vibration seem to originate? First thought was drive shaft U joints. Or front axle U joints. Link to comment Share on other sites More sharing options...
1989commanche Posted October 13, 2020 Share Posted October 13, 2020 Check the driveshaft U joints for slop. Link to comment Share on other sites More sharing options...
omega_rugal Posted October 13, 2020 Share Posted October 13, 2020 2 minutes ago, 1989commanche said: Check the driveshaft U joints for slop. This Link to comment Share on other sites More sharing options...
Wounded_Fighter Posted October 14, 2020 Share Posted October 14, 2020 My buddys MJ had a similar issue mostly under gear 2or higher and real bad in a turn. driveshaft had slop... This happened... Apparently he still covered 200 miles like this... without knowing... Link to comment Share on other sites More sharing options...
Tex06 Posted October 15, 2020 Author Share Posted October 15, 2020 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 comment Share on other sites More sharing options...
Tex06 Posted October 15, 2020 Author Share Posted October 15, 2020 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... Apparently he still covered 200 miles like this... without knowing... Holy............ Link to comment Share on other sites More sharing options...
omega_rugal Posted October 15, 2020 Share Posted October 15, 2020 7 hours ago, Tex06 said: What confuses me is that the vibration completely goes away at any speed if I let off the gas or press in the clutch. wihtout the engine pushing, the joint is free to rotate Link to comment Share on other sites More sharing options...
MiNi Beast Posted October 16, 2020 Share Posted October 16, 2020 I'm thinking bent fingers on pressure plate. or pilot bearing. how in depth was your clutch repairs? Link to comment Share on other sites More sharing options...
Tex06 Posted October 19, 2020 Author Share Posted October 19, 2020 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 comment Share on other sites More sharing options...
Tex06 Posted October 19, 2020 Author Share Posted October 19, 2020 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 comment Share on other sites More sharing options...
89 MJ Posted October 19, 2020 Share Posted October 19, 2020 Does the truck seem down on power compared to before the vibration started? When my truck misses, it seems to shake a little bit. Link to comment Share on other sites More sharing options...
Tex06 Posted October 19, 2020 Author Share Posted October 19, 2020 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 comment Share on other sites More sharing options...
MiNi Beast Posted October 19, 2020 Share Posted October 19, 2020 screw in a tire? Link to comment Share on other sites More sharing options...
Pete M Posted October 20, 2020 Share Posted October 20, 2020 I had a rear ujoint go bad in my Liberty that gave vibrations under load, but went away if I coasted. Link to comment Share on other sites More sharing options...
Tex06 Posted October 20, 2020 Author Share Posted October 20, 2020 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 comment Share on other sites More sharing options...
Pete M Posted October 20, 2020 Share Posted October 20, 2020 it was super, duper obvious on the Libby just by grabbing the driveshaft and shaking. Link to comment Share on other sites More sharing options...
blakews2217 Posted October 20, 2020 Share Posted October 20, 2020 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 upSent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
ghetdjc320 Posted October 21, 2020 Share Posted October 21, 2020 Double check your engine to tranny bolts and tranny to tcase bolts. I had tranny bolts be a little loose that caused this issue. Link to comment Share on other sites More sharing options...
Tex06 Posted October 21, 2020 Author Share Posted October 21, 2020 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 comment Share on other sites More sharing options...
MiNi Beast Posted October 21, 2020 Share Posted October 21, 2020 ive driven across the swamp yea. Link to comment Share on other sites More sharing options...
Wounded_Fighter Posted October 21, 2020 Share Posted October 21, 2020 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 comment Share on other sites More sharing options...
ghetdjc320 Posted October 21, 2020 Share Posted October 21, 2020 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 comment Share on other sites More sharing options...
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