TJ vibrates....that can't be good

    My 98 TJ has developed a vibration when the engine is under a load, but the vibration is absent while coasting. A friend of mine thinks it may be my universal joint(s). I've had the Jeep lifted 4 inches since mid-July and aligned right after the lift was installed. The only major thing that has happened since then was the GWNF wheeling trip. This is apparently not an alignment problem or a wheel balance problem, but I intend to have the front wheels re-balanced soon to eliminate that possibility. Unfortunately, I'm not too swift with auto mechanics.


    So, I'm reaching out to the DEJA TJ experts. Is anyone familiar with the drivetrain vibration that occurs when U-joints start to go bad? If so, would you be willing to take my TJ for a test spin and give me your opinion on what my problem might be?


    Also, my friend wasn't sure if 98 TJ's disconnect the 4-wheel-drive at the transfer case or at the hub. Which is it? Thanks. :driving:

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    Quote from Keith_C


    Check your drive-shafts for dings too, you could have scraped one going down the steps.


    Running 4" of lift with no SYE/CV driveshaft is borderline.


    Ok, I'll bite....what's "SYE/CV" driveshaft?


    I'll look as closely at the driveshafts as I know how to do to see if they are dinged. When you say "dinged" I assume you mean "bent" a little, right? Are you saying the driveshaft can also get dimpled from the rocks so it's no longer a smooth cylinder shape? If so, I didn't know that.


    What about the U-joint theory? Not likely??

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    Very good point! From what you are telling us, if you had dinged your rear drive shaft on the trail three weeks ago and the vibration just started, then you would have noticed the vibration right away. What they are referring to is just like your tires, your drive shaft is balanced so when it spins at high speeds there is no vibration. If there is a ding or dent from hitting it on the trail, then the balancing is gone and the vibration starts. Like a washer that has too many clothes to one side. The weight gets shifted and a bad vibration starts. The "all of a sudden" vibration says to me that something just started to go. Yes it very well could be a U-joint. My rear u-joint was only vibrating under load and finally went at highway speeds on the way to work, before I could get a chance to fix it. The shaft flipped around under the rig and cracked the casing on my T-Case. Try this, Lie under your jeep and with out turning your rear drive shaft wiggle it at both ends, by the U-Joints, and see if there is any play. Spicer makes a U-Joint that is (Ha Ha) NOT greaseable. I don't care how well their made, dirt will get up in them and you will NEED to be able to grease them.


    SYE/CV Drive shaft = Slip Yoke Eliminator / Central Velocity Drive Shaft
    What a mouth full to say and type. Now you know why they Abbreviate. LOL
    It's a drive shaft replacement that also has a CV Joint, *(Double U-Joint)* in the drive shaft to allow for steeper drive shaft angles. Coming out of your T-Case and going to your rear Differential, your drive shaft should be in as strait of a line as possible. Think of it like a swivel on you socket set. The U-Joints and CV Joints allow for *SOME* angle of entry and departure for flexing and movement. When lifted, this angle gets a whole lot steeper and wears out your U-Joint/CV Joints a lot quicker due to the added force and stress on them. Vibration is also another added factor, for your drive shaft, when your rig is lifted. Did your lift kit come with a T-Case drop kit? That would be two long bars you put in as spacers between your frame rails and your T-Case skid mounting bracket to *DROP* your T-Case and lessen the angles in your drive shaft U-Joints. If not you can purchase a kit for about $40.00 and lessen the angles and hopefully eliminate the vibration. Hope this helps.


    Let me know what you find out.
    John

    There is nothing that can't be fixed if you throw enough money at it,

    Edited once, last by jonzjeepyj ().

    It's all because of those ^%$#% logs. :cuss:

    "I mean, I've always been a libertarian. Leave everybody alone. Let everybody else do what they want. Just stay out of everybody else's hair." - Clint Eastwood -

    Quote from jonzjeepyj


    Try this, Lie under your jeep and with out turning your rear drive shaft wiggle it at both ends, by the U-Joints, and see if there is any play.


    I was not able to move my rear drive shaft at all -- no turn, wiggle or anything else. The U-joints seem to be firm. The rear U-joint (near the differential) has some grease stains, but I'm inferring from your post that this is normal if it's a greaseable U-joint. I would post pictures if I thought it would help, but it sounds like everyone on this thread knows what it looks like.

    When engaged in conversation with a fool, be sure he is not similarly engaged.
    Chief, DEJA Grammar Police

    KnoksRents Wrote...

    Quote

    Actually CV=Constant Velocity


    Thanks for correcting me.


    Keith_C and I both asked, Did you Kit come with a T-Case lowering kit? Was your T-Case Lowered?

    There is nothing that can't be fixed if you throw enough money at it,

    Edited once, last by jonzjeepyj ().

    Quote from jonzjeepyj

    Thanks for correcting me.


    Keith_C and I both asked, Did you Kit come with a T-Case lowering kit? Was your T-Case Lowered?


    Usually you can tell, if there is a space between your frame and your skid plate. If there is a space, you have a t-case lowering kit. If your skid plate is agenst the frame then you probably don't. Spacers usually look something like this: (for example)
    http://www.quadratec.com/products/16006_100.htm
    http://www.quadratec.com/products/16090_300.htm


    I did mine with some store bought washers between the skid and frame.

    Here is a pic of mine that I just installed. I also included a pic of my rear drive shaft. Notice how straight and in line it is after the T-Case drop was installed. Notice the box tube in between the frame rail and the T-Case skid bracket...




    There is nothing that can't be fixed if you throw enough money at it,

    I think my transfer case is not lowered. I don't have the big spacer like jonzjeepyj has shown in his photos. The skid plate is not flush up against the frame, but the gap between the frame and the skid plate is about 1/2 inch at most.


    So, who's the resident DEJA U-joint rebuilder guy? I've got an appointment with Delaware Tire tomorrow at noon for them to "assess" the situation (for free), but as you can imagine I'm not too excited about giving them a blank check to do the work. I'm told the U-joints can be disassembled and rebuilt, but I'm realizing now that that would only be a temp fix, and I'll be faced with doing it again unless I do one of the suggested permanent fixes.


    To tell the truth, certk9 knows my TJ better than I do, and he's the one who did the 4" lift. I was just his helper. So, I'll connect with him when possible.

    When engaged in conversation with a fool, be sure he is not similarly engaged.
    Chief, DEJA Grammar Police

    Edited once, last by Chief57 ().

    new u-joints are about 10 bucks. I had the same problem before and i finally figured out that the rear axle yoke was "egged out" meaning that the yoke was too wide for the u-joint, causing the driveshaft to have play and create vibrations. I replaced the yoke and all of the u-joints and the problem is gone!

    Quote from Jeepcreep02


    new u-joints are about 10 bucks. I had the same problem before and i finally figured out that the rear axle yoke was "egged out" meaning that the yoke was too wide for the u-joint, causing the driveshaft to have play and create vibrations. I replaced the yoke and all of the u-joints and the problem is gone!


    That sounds encouraging! Was your problem just like mine....a vibration when you give it the gas, but fairly smooth (normal) while coasting? Should I just have Delaware Tire knock it out tomorrow while it's in their shop? How much $$ could we possibly be talking here? Jim

    When engaged in conversation with a fool, be sure he is not similarly engaged.
    Chief, DEJA Grammar Police

    we took some pics of the setup tonight - i didn't feel much play in the ujoints...but that doesn't necessarily mean they aren't the culprit. the vibes definitely are on the acceleration and not on deceleration; so it may be a combination of a sloppy ujoint and also just too much angle on each end. he has about 1/2" of a drop in there right now but with 4" of lift he may need the whole 1" drop. here are the pics i took.


    1/2" spacer sandwich


    not the best but nothing too severe either


    closeups - neither are greaseable (or if they were the zerks are missing and the holes packed with dirt since i couldn't feel them)

    Quadna, thanks! That's one heck of a camera you have. Per our conversation, I'll start pricing some Spicer brand greaseable u-joints, and maybe also a MML kit also for later after I fix this immediate problem.

    When engaged in conversation with a fool, be sure he is not similarly engaged.
    Chief, DEJA Grammar Police

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