Post-lift vibrations, bad driveshaft angles? - JeepForum.com

 
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post #1 of 12 Old 06-14-2012, 01:01 PM Thread Starter
econstantin
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Post-lift vibrations, bad driveshaft angles?

Hi, I just recently put on a OME lift (4x 36R)... it appears that I got somewhere almost 4" of lift out of it (sounds big, but bottom of rocker panels now sit at 22.5" on BFG TA/KO 31s, see the pic here).

When it was installed, we only anticipated 2-3" and so didn't do a TC drop right away. I also had smaller tires on it (Wrangler Radials P235/75R15), which may have made the lift seem a bit smaller. We test drove it and there was minimal vibration (only when coming off the throttle and engine-braking), and we expected the lift would a settle bit.

Over the past two days, the vibrations have gotten significantly worse. The gear shifter vibrates a lot when accelerating from a standstill, up to somewhere between 5-10mph, after which it settles down. While cruising or at highway speeds, I can still feel a bit more vibration that pre-lift, but overall it's acceptable.

I've been researching a bit more on driveline angles (I'm a newbie to this), and took some pictures this morning (see attached).

The current angles seem to be 'exactly wrong'? (TC output & rear-pinion are at different angles, whereas they should be as close to parallel as possible?)

The rear axle leafpack came with a small shim on it, and the u-bolt kit came with 2deg shims which we added as well (so probably around 3-4deg total). This seems to have the effect of tilting the pinion upwards, and creates a different angle?

In looking at various articles/posts, the current driveshaft angles seem like they'd be appropriate for a CV (double cardan) driveshaft, but not a stock U-joint driveshaft?

I'm also wondering if the angle of the TC case / slip-yolk seems normal, or if it's evidently under strain?

I appreciate any help & insights on this. Thanks

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photo-1s.jpg   photo-2s.jpg   photo-3s.jpg   photo-4s.jpg  
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post #2 of 12 Old 06-14-2012, 01:21 PM
mrdeath2000
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it appears you either need to lower the end of your TC or lower the yoke of your pinion to get rid of the vibes, but you'd be close to binding.

Pick up a $10 angle finder and spin the shaft another 90* so the u-joint straps on your pinion are on the bottom and top (not the sides like the picture). It makes it easier to see your angle and that's how you're going to measure it.

You want the angles as close to paralell as you can, with the pinion maybe 1-2* lower. That would be ideal. However, with the lift you really need an SYE, and may have to live with some vibes to avoid binding/snaping a ujoint when flexing/compressing/articulating.

93' YJ 2.5L, 4.88's, 8.8, E-Locker & LSD

Last edited by mrdeath2000; 06-14-2012 at 01:35 PM. Reason: lower TC not raise.
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post #3 of 12 Old 06-14-2012, 01:29 PM Thread Starter
econstantin
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Worth trying a TC drop to see if that improves things?
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post #4 of 12 Old 06-14-2012, 01:29 PM
Mark05059
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im looking that the transfer case needs to go lower so that the angle is less steep.. I may be mistaken though.

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post #5 of 12 Old 06-14-2012, 01:34 PM
mrdeath2000
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yea, i meant TC down LOL, not up.

TC drop is certainly worth trying. after you do it, cycle the shaft by hand if it looks close to binding, just to be safe.

93' YJ 2.5L, 4.88's, 8.8, E-Locker & LSD
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post #6 of 12 Old 06-14-2012, 01:43 PM Thread Starter
econstantin
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Some more pics as requested.

Going to try TC drop now..
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post #7 of 12 Old 06-14-2012, 01:49 PM
mrdeath2000
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Yea, try the drop. It may not be perfect, but it will help for sure.
Doesn't look like you will have a binding issue, looks pretty clear.

93' YJ 2.5L, 4.88's, 8.8, E-Locker & LSD
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post #8 of 12 Old 06-14-2012, 01:55 PM
crackedcornish
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some basic info on drive shaft/joint angles here...http://benmlee.com/4Runner/driveline/U-JOINT.htm

it's about Toyota's but a lot of it is applicable here as well...here's a snipet




3 Ways to Correct Driveline Angles

There are three pratical ways to solve dirveline vibrations. They are: u-joint with opposite angle in the top picture (most common), u-joint with same angle, middle picture, which is less common and cv-joint on the bottom picture which is quite common too.

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post #9 of 12 Old 06-14-2012, 01:58 PM
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The transfer case drop will fix the issue for sure. Also swapping out the double shims for a single shim in the rear will decrease axle wrap.

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post #10 of 12 Old 06-14-2012, 06:32 PM Thread Starter
econstantin
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TC drop fixed the vibes. Gears feel a bit funky now though (apparently normal).

Thanks for all your replies & help!
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post #11 of 12 Old 06-14-2012, 09:59 PM
Anticanman
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Quote:
Originally Posted by econstantin View Post
TC drop fixed the vibes. Gears feel a bit funky now though (apparently normal).

Thanks for all your replies & help!
The funky feeling is normal. Like I told you about lifting a jeep, nothing will be the same once you do it. And the jeep bug bites hard after that.

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post #12 of 12 Old 06-14-2012, 10:28 PM
AmmitOsiris
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Mine was the same way, my springs(same as you 36r on all 4 corners) settled in about a month ( with no shocks) once the springs settle your springs will give you 3.5 inches of lift. Also tc drop isn't hard I did it in my garage with a jack. Happy installation
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