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drive vibration

Discussion in '80-Series Tech' started by concretejungle, Dec 1, 2003.

  1. concretejungle

    concretejungle SILVER Star

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    Sorry guys i've been away from my computer for a week. I tried the search and no luck. I remember a week or two ago someone asking about vibration after they let off the accelerator at highway speeds after a lift. I've got the same issue and was wondering what was said in that thread. Anyone point me to the right topic? ???
     
  2. waldrtw

    waldrtw

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    I put my lift on last week and i have the smae problem. When I back off the pedal going down hill and give it just alittle gas it vibs like crazy but goes away has I push the gas more. It sounds more like the front drive shft is falling apart than a vib.

    tim

    Let me know what the fix is. I guess a new front shaft.
     
  3. jeffnordeen

    jeffnordeen

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    Hey, I was the original sender of the vibration message. In talking off-line with some of the 80's cool group list, I found out the following:

    1). Most, if not all of the vibration will go away once I get the caster correction bushings on. I just haven't got around to that yet.

    2). I was advised by most people that getting an alignment is a good idea after completing a suspension upgrade (and new tires for most folks).

    3). If you still have a vibration after completing the above, Christo recommended a double cardan front driveshaft. You can find them at sleeoffroad.com under drivetrain products.
     
  4. concretejungle

    concretejungle SILVER Star

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    I've got the caster bushings in. The mechanic who put my lift on also suggested alignment of the front end but it tracked very straight, so i haven't oppted for that yet. What would the double cardan driveshaft do? It wouldn't change the drive shaft angle would it?
     
  5. landtank

    landtank SILVER Star

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    How many miles? The first thing to do is to closely inspect your u-joints. They tend to wear in a football (American) shape because of the limited travel during use. Now that you have raised the vehicle the travel has increased and also shifted in comparison to the wear area of the joint. I have the OME heavy springs up front and back as well as a 1" spacer up front with no vibrations. However I also have a Kaymar rear bumper and ARB front bar.

    What lift did you put in and what do you have for accessories?
     
  6. PHAEDRUS

    PHAEDRUS

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    it will take it from an a to b to an intermediate. the cardan just allows for smoother transfer of power at extreme angles. they are a bit spendy if memory serves but better now than when the driveline grenades.
    Dave
     
  7. concretejungle

    concretejungle SILVER Star

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    140,000 miles and going strong. I got the 2.5" medium load lift with only the ARB roof rack. I'm doing an oil change this weekend, maybe a little amsoil grease will help.
     
  8. the shed guy

    the shed guy

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    I did a 4" lift on an 80 last week, and we did the cater mod that Christo is working on, the front shaft started vibrating after the lift, and once we made a 5 deg caster correction, the vibe got worse, will be fitting 2 new Toyota uni's to the front shaft, less than $100 Aus, and some time.

    Will see if this fixes the vibration.
     
  9. landtank

    landtank SILVER Star

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    140k, I'd be thinking universals. At 118k my front univerasal and slip yoke on the rear shaft was shot. I just replaced the whole shaft.

    If you have the CDL, remove a shaft and see if the vib goes away. After doing both ft and rr shafts you should be able to pinpoint the offending shaft.
     
  10. alia176

    alia176

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    Guys,

    I failed to see how castor correcting bushings help the drive shaft vibes ??? Think about it, the bushings are rotating the diff pinion flange back toward the ground and increasing your UJ angles. At the same this is also increasing your castor angle at the same time, thereby giving your steering a stronger return to center feel, less wandering at speeds, etc.

    As somone suggested, check the condition of the UJs and replace them if necessary. Don't just shove bunch of grease in there! DC (double cardon) driveshaft should eliminate the vibes due to the fact that they split the angles seen by the UJs at the T case output shaft. Another words, as you lift your vehicle higher, this angle is getting larger, a DC driveshaft simply cuts this angle by 1/2. Consequently, your UJs are happy again and hopefully your vibes are reduced. From my past experience, castor bushings (or any other castor correcting methods) and DC front driveshaft go hand in hand. You get good steering and no (almost none) vibes. Don't forget to put loctite on the driveshaft flange bolts even if you are using nyloc nuts. If these nuts/bolts become a little loose, then you get the same grrrrrrrrnkk type vibes under sudden decel.

    DC driveshaft can be made at most driveline shop for a decent price. Simply take your driveshaft to them and they can convert yours to a DC driveshaft or make you a brand new one for prolly less than 300 $US. Or you can buy them from places like Tom Woods (www.4xshaft.com) or Six States Distributor (http://www.sixstates.com/).

    As always, no offense to anyone!

    :cheers:
     
  11. sleeoffroad

    sleeoffroad Supporting Vendor

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    The reason the front shaft vibrates is not as much the angles that is to big, but the angles are not the same.

    If you look at the front shaft on the 80, you will see that it is remarkable flat. Lot more so than the rear.

    The diff flange and the tx case flange is located like this \------/ where the two angles are the same. As you increase the lift, the front angle goes closer to 0 and the rear increases. When the caster is added back in depending on the situation, the vibrations may or may not go away. If you draw this out, you will see that if you increase the lift enough the angles will eventually look like this
    /----/ and you migth not have vibrations again.

    Also, yes any shop can do the cv conversions. Early on, we used Spicer style CV's. All of them failed, some even with only 5k miles on them. If you can do it with a Toyota or Koyo style joint, go for it.
     
  12. NW-sickboy

    NW-sickboy

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    I have done all of this....yes all of the aformentioned (minus the CDL and driving with one Drive shaft) and i still have vibration issues. my brother(drives a 91) has the same lift (J-spring 4 inch) and has no issues. i (in a 97)am now doing custom control arms up front and i have the DIY joints for the rear control arms. i will keep you up to date. the only thing i prolly wouldnt have done is the front double cardan shaft but maybe it did more than i know but cant tell because of all the rear vibrations issues i have...........by the way i think there are 2 issues being stated here and its easy to get them confused. one is vibrations at freeway speeds. the second is a noise you get (i think it is grinding of some sort) when you let off of the accelerator at those speeds. i think it is 2 different issues. could be wrong. but i think there are 2 issues at hand.
     
  13. concretejungle

    concretejungle SILVER Star

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    You guys are right. Probably need to service or replace the U-joints. I don't notice any noise during the vibration, which i guess is a good thing. The thing that is strange is that the first month i had the lift i never felt the vibration. It's only recently started acting up.
     
  14. alia176

    alia176

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    Good explanations, thanks.

    As someone said earlier, the "ovaling" of the UJs as they age does make sense. I'm curious as to what's causing Sickboy's rear vibes. I have a friend with a D110 who's experiencing the same exact issues on the rear DS. We've tried several things to no avail. So the search continues.....
     
  15. NW-sickboy

    NW-sickboy

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    I am pretty convinced it is my rear pinion angle. i have just put off buying the DIY joints fromslee becuase i wanted to do more of a "long arm" for my control arms than just make them adjustable. i am really confident it will fix it.
     
  16. ginericLC

    ginericLC Wagon Wheeler! SILVER Star

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    Also something that folks seem to be forgetting is a lift exaggerates any preexisting conditions that a rig has. If there are alignment issues prior they will be exaggerated after the lift. If U joints are worn they will be exaggerated after the lift. I like Christos description on the driveshaft vibration what he left out about if you lift it enough and get the driveshaft so it is /------/, it will handle like crap because the caster is screwed up. I suppose you could cut and turn the knuckles to correct it.
     
  17. sleeoffroad

    sleeoffroad Supporting Vendor

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    Long arm on the rear would get rid of a lot of rear steer. However the gas tank is in the way to go forward with the upper arms. If you go backwards, you need to cut more body on the back. Also, what I would really like on the shortbus is to get the rear bottom arms to mount on the side of the frame and get rid of the mount. I get hung up on that a lot.

    Also, if you really want to get the travel from the rear, drop the swaybar and extend the shocks into the cab. Just fyi. Learned a lot on how the 80 stock suspension setup can be maxed on the ShortBus. Drop a line sometime and we can chat.