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Old 05-07-2013, 11:37 AM   #1
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Driveline Vibrations after Lift

Hey Guys,

I lifted my 99 Wrangler 4" recently. The transfer case was dropped 1", as I have not got the funding to do a SYE/CV at this time - though it is in my plan for the future. I have fully adjustable upper and lower control arms in the front and rear.

Immediately after the lift, the vibration was more than a little noticeable. I have done some research and learned that the angle coming off of the slip yoke should match the angle at the rear differential - if I am understanding correct. Using an inclinometer, i had a reading of 10 degrees at the slip yoke and 15 degrees at the rear differential. We decreased the length of the upper control arms, to match up the rear differential angle to 10 degrees.

I still have noticeable vibrations. I have determined it to be the driveline, as when I am on the road and push in the clutch, she coasts smoothly. The vibrations only occur when the engine is engaged.

Any ideas on what the next steps are to eliminate or minimize the driveline vibrations?

Thanks,
Rufus

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Old 05-07-2013, 12:03 PM   #2
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I don't know exactly - and you've done angle measurements - but lifting 4" is just too much for a transfer case drop. A 1" drop is fine for lifting 2-3 inches, but it becomes not enough for some TJs after you get more than 3". 4" almost always requires the SYE from what I've read.

Have you considered lowering the TC even further? If you're using a drop kit you can add washers to get a bit more lowering out of it. It's going to suck losing all that clearance, but better than blowing your joints apart.

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Old 05-07-2013, 01:52 PM   #3
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I have considered additional drop to the transfer case - but I wanted to ensure that was the appropriate action to take, before taking it.. I have read numerous posts with the TC drop being done without driveline vibes or having to drop it lower, so I wanted to see what else to check. So far, through other avenues, I have been advised how to check the drive shaft u-joints to ensure they are not worn or bad..
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Old 05-07-2013, 03:29 PM   #4
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Of course, worn U joints could cause vibration.... but if you didn't have any issues before you lifted it and now you do, you can pretty much rest assured it is due to the lift and not worn parts.

No, lowering the transfer case isn't the appropriate action to take. The appropriate action would have been to not lift it that much until you could afford the SYE. But now that you have, I'm not sure there are any other options available to you except maybe a motor mount replacement which may or may not work, and is not really adventageous when you finally get your SYE.
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Old 05-07-2013, 03:52 PM   #5
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Pull the rear shaft go for a ride in 4h .
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Old 05-07-2013, 04:03 PM   #6
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Quote:
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Pull the rear shaft go for a ride in 4h .
+1

That will tell you if it is the rear driveline for sure.

Almost always a SYE kit is needed for 4 inches, some get away with it but it is a good idea to go with it. I know sometimes money is tight but it is better to save up and do it right the first time or you will end up spending more in the long run. I know from experience.
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Old 05-07-2013, 07:26 PM   #7
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I lifted mine 4" about a year and a half ago, and only recently put in the SYE. I had no vibes with the tc drop. The difference is that my tc was dropped 1 1/2". You are right about the angles, pinion should be the same as tc with a slip yoke.
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Old 05-07-2013, 09:59 PM   #8
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I am surprised to learn that a tc drop is not adequate with a 4" lift, as I understood from my reading that with this list it would be an either/or option... That said, I have eliminated ujoints as the problemvthis evening. I measured the angles again and may have had a bad reading.. the bracket that connects ujoint at the axle end has a "lip" that can throw off the angle reading by 1-2 degrees. This mat be my problem.. Now I just need time to mess with it and see if that fixes it...
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Old 05-08-2013, 11:27 AM   #9
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I just went thru same DL vibration deal with 04 TJ. I installed RE7003 3.5" lift w/o SYE & CV Driveshaft. Installation instructions indicated SYE & CV Driveshaft was reccomended but talking with others who indicated I could get by w/out the SYE & CV Driveshaft. Next I tried rear upper Adj CA's first but still had vib. I finally purchased Advanced Adapter SYE and Tom Woods CV DS and my DL vib's are gone. Can get kit from 4x4groupbuy for $466
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Old 05-08-2013, 12:08 PM   #10
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Quote:
Originally Posted by RufusT View Post
I am surprised to learn that a tc drop is not adequate with a 4" lift, as I understood from my reading that with this list it would be an either/or option... That said, I have eliminated ujoints as the problemvthis evening. I measured the angles again and may have had a bad reading.. the bracket that connects ujoint at the axle end has a "lip" that can throw off the angle reading by 1-2 degrees. This mat be my problem.. Now I just need time to mess with it and see if that fixes it...
A 1" tc drop is usually never enough for a 4" suspension lift (except for an Unlimited TJ), I don't know where you got the idea it is... except perhaps from an unscrupulous suspension lift dealer. 4" of suspension lift creates excessive u-joint angles on the rear driveshaft. So excessive that a t-case drop is usually nowhere near able to counteract them. That is the height at which a SYE kit and CV driveshaft is strongly recommended. Which is why I mentioned some unscrupulous suspension lift manufacturers won't mention that because of the expense... they'll wait until after the suspension lift is installed & the customer is having bad vibrations before they break that news to them.

You MIGHT be ok if you now also install a set of 1" taller motor mounts like the rubber mounts from Brown Dog or M.O.R.E. 1" taller motor mounts (aka MML... motor mount lift) can combine with a 1" t-case drop to sometimes be enough to stop the vibes from a 4" suspension lift.

However, the best/correct method to eliminate those vibrations is to install a SYE kit & CV driveshaft. Which also requires adjustable length upper rear control arms so the rear axle's pinion angle can be raised to match the requirement of the aftermarket CV driveshaft. The combination of a SYE kit & CV driveshaft completely eliminates the excessive u-joint angles & also allows you to get rid of the t-case drop which reduces ground clearance.
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Old 07-02-2013, 08:12 AM   #11
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I spent some time working on the Jeep last weekend to fix some noises that had developed. One of the problems was an extremely worn rear ujoint. Replacement of this joint not only eliminated the sounds, but also eliminated my driveline vibration.

I think the ujoint was already wearing before my lift, as I had a slight vibe beforehand. The increased angle likely made it worse.

I thought updating would be a good idea, in case someone else has a similar problem in the future.

RTP

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