Vibration after 2.5Ē Lift - Need Advice on Options - JeepForum.com
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post #1 of 86 Old 03-10-2020, 02:37 PM Thread Starter
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Vibration after 2.5Ē Lift - Need Advice on Options

Apologies for long post, trying to be thorough.

Just installed a new 2.5Ē lift kit and I am now experiencing what I suspect are driveline vibrations only when starting off in 1st gear slowly, and usually when making a full turn (seems like both left and right). It doesnít happen every time, and isnít perceptible when at speed, although I just got it on the road and havenít put many miles on it yet.

My springs were wrecked in an accident so I decided to go with a whole new lift kit, and installed rough countryís 2.5Ē lift kit. I know, I know, I should have went with the BDS lift. I didnít realize that until I installed it, but I really needed to keep costs down initially anyway because I wasnít sure what else I was gonna find and needed to keep room in the repair budget. Surprisingly though, I will say it rides a hell of a lot better than what the PO had on there and so far I like it. Maybe the springs have improved because it doesnít feel stiff at all, at least not on the road. Next time, I will try BDS.

I did not have any driveline vibration prior to lift kit install, and thought I was replacing a similar size lift, BUT who knows what I removed - it looked like a mix of components since shocks didnít match. Height does seem comparable though overall. I did also install a new tranny mount which Iím sure is contributing since going back to the correct thickness mount would raise the TC.

Anyway, the RC lift kit came with substantially thicker shims than what was on my rear axle before. The rear diff pinion is now pointing almost at the TC output, when before I believe they were close to parallel to each other before. I checked the angle on my rear driveshaft with my iPhone and it is showing -17 degrees. I also noticed a little play in the U-joint as the diff end. It has a very small amount of wiggle to it. I greased everything up last night and it is still doing it. You can also tell the front and rear driveshafts are extended longer now. I havenít tried four wheel drive yet so I am focusing on the rear only right now.

My question is, what is the smart fix here? Iíve read about TC drops and CV shafts with slip yoke eliminators. The transfer case drop seems like it could introduce other issues. For example, my 75 has the toolbox under the pass seat and the TC Shifter hits it when going into 4-LO and Iím worried I wonít be able to shift into gear if I drop the TC. Iím also worried about the engine fan if I drop the TC because I have a shroud installed.

I would like to do this right. I donít do a ton of wheeling and definitely not overly technical stuff, some beach driving and fire roads, but I use the crap out of my Jeep driving her all over and she does see trails. I want a reliable setup. I have no idea how old my U-Joints are and thinking at a minimum I should replace them all and if Iím doing that, itís the perfect time to swap the shaft.

For you guys that love your jeeps as much as I do, what would you do here? Go with a Tom Woods CV shaft and call it a day, or Iím over thinking the concerns with the TC drop and I should save my money and go with that. Skyjacker has a nice kit for $40, versus $200+ for a CV shaft not including the SYE. Or is there another option Iím missing?

I really appreciate any advice you can offer here.


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post #2 of 86 Old 03-10-2020, 04:14 PM
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That picture says it all. You need a double cardan drive shaft, as the pinion and the transfer case output are supposed to be parallel. The shims they gave you corrected every issue I had with my 2.5 lift but the drive shaft design.

Simple fix, a new driveshaft.
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post #3 of 86 Old 03-10-2020, 04:29 PM
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Double cardan with only a 2.5" lift seems like an extreme measure...may be necessary with yours but before you run out and buy one are the shims supplied with the kit degreed/angled? In the pic it looks kit they are angled and pointing your diff up more than original. If so you could possibly try reversing the shim direction? Avoid a trans lowering kit.

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post #4 of 86 Old 03-10-2020, 04:29 PM Thread Starter
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I had a feeling thatís where this was going. Iím shocked things are so different. I really thought I was replacing a similar height lift and wouldnít have a problem. Guess it wasnít what I thought it was.

It seems like removing the shims would make the pinion parallel again, but then the driveshaft angle would just be worse.

Iím guessing based on your response a TC drop ainít gonna do it either. Iím planning on calling Tom Woods tomorrow. Time to start reading up on how to replace a drive shaft.

Quote:
Originally Posted by Cutlass327 View Post
That picture says it all. You need a double cardan drive shaft, as the pinion and the transfer case output are supposed to be parallel. The shims they gave you corrected every issue I had with my 2.5 lift but the drive shaft design.

Simple fix, a new driveshaft.





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post #5 of 86 Old 03-10-2020, 04:34 PM
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Quote:
Originally Posted by PottsyCJ5 View Post
I had a feeling thatís where this was going. Iím shocked things are so different. I really thought I was replacing a similar height lift and wouldnít have a problem. Guess it wasnít what I thought it was.

It seems like removing the shims would make the pinion parallel again, but then the driveshaft angle would just be worse.

Iím guessing based on your response a TC drop ainít gonna do it either. Iím planning on calling Tom Woods tomorrow. Time to start reading up on how to replace a drive shaft.
The drive shaft angle is not the issue. You want your pinions parallel.

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post #6 of 86 Old 03-10-2020, 04:54 PM
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Before you buy a new driveshaft, remove the shims, replace your ujoints and test drive. You should not have play in your ujoints.

I do not suspect you are at your max operating angle with your lift and no shims. You could leave the shims in and spring for the CV driveshaft but you may not need it so why waste money.

Do not do the TC drop. The problem is easily worked out with what you got.
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post #7 of 86 Old 03-10-2020, 05:51 PM Thread Starter
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Vibration after 2.5Ē Lift - Need Advice on Options

Yes, the kit came with much thicker shims than I had before. Here is a photo of the shims, not sure what degree they are to be exact though. I assumed they were necessary - they came pre-installed on the leafs.

If I am 17 degrees on the driveshaft now though, wouldnít removing the shims and bringing the Diff pinion back it parallel make the overall angle of the driveshaft even more severe/steep?

I thought my driveshaft was supposed to be somewhere around 10 degrees or less.

Should I be concerned about the extra amount the driveshaft is extended at rest? It looks like about a 1/2Ē.

Here is a pic of the driver side shim looking back at it. The thick side is towards the front of the Jeep.



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post #8 of 86 Old 03-10-2020, 05:51 PM
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Save yourself time and work, just get the new driveshaft. Taking the shims out will increase the angle of the driveshaft.

When I installed my 2.5 lift, the yokes were binding against each other from the angles being so extreme. May not be an issue in 7s, but on my 5 with the already short driveshaft, it was.

You'll be happier with the double cardan setup anyway, less vibration than you would have trying to just run what you have.

To replace the drive shaft with a double cardan style, you install a new yoke on the transfer case and bolt the new drive shaft in. The new driveshaft will give you new u-joints, so even if your current has play, they're not going to be an issue.

If you have straps and bolts for the rear yoke, get a new strap kit to install the new driveshaft. The straps stretch over time, allowing the cap to spin in the yoke. If there is play in the yoke where the caps sit, put a new yoke in.

I'd put new pinion and transfer case output seals in while yokes are off.
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post #9 of 86 Old 03-10-2020, 06:05 PM
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I don’t disagree that a CV shaft would correct the problem in the easiest way, with the least amount of work as the driveline currently rests. If prior experience shows that a 2.5” lift will cause too much of an angle for the ujoints then by all means do the CV and be done.

I run CV’s front and rear on my setups but mine are a lot different over all.

You would not go wrong in keeping what you have and doing a CV.
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post #10 of 86 Old 03-10-2020, 06:38 PM
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Quote:
Originally Posted by PottsyCJ5 View Post
Yes, the kit came with much thicker shims than I had before. Here is a photo of the shims, not sure what degree they are to be exact though. I assumed they were necessary - they came pre-installed on the leafs.

If I am 17 degrees on the driveshaft now though, wouldn’t removing the shims and bringing the Diff pinion back it parallel make the overall angle of the driveshaft even more severe/steep?

I thought my driveshaft was supposed to be somewhere around 10 degrees or less.

Should I be concerned about the extra amount the driveshaft is extended at rest? It looks like about a 1/2”.

Here is a pic of the driver side shim looking back at it. The thick side is towards the front of the Jeep.
The shim angle as it is with thick end to front is the issue. It is exaggerating the pinion angle upwards. Reverse the shim orientation and it will bring your pinion back close to parallel - or try removing shims entirely. The shaft angle and some extension should not be a problem at all with that size lift unless you plan on really extreeeeeeeme wheeling. On the front axle the shim with thick end towards front is possibly fine,depending on angle, as it helps maintains correct castor range for steering.

EDIT: are the rear springs installed the correct way around? Just an afterthought.

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post #11 of 86 Old 03-10-2020, 07:07 PM Thread Starter
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Great feedback. I really appreciate it. It would be a hell of a lot easier to go the driveshaft route. Iím not crazy about the cost but will be pretty frustrated if I go to the effort to remove the shims and still end up having issues. Itís sounding like even if removing the shims improves things I might be better off overall with the CV shaft. If thatís the case, Iím leaning towards just doing it and gaining the added benefits of things being super smooth and trouble free.

If I go the CV drive shaft route, any idea if the Dana 20 on a 75 would have a 10 or 26 spline yoke?

Is it a complicated job replacing the yoke with the SYE on the Dana 20? That seems like the only tricky part. Is it just bolt on for the most part?

The front springs didnít come with shims and the pinion up front still looks close to parallel to the floor. I havenít had it in 4-wheel yet after the accident. My plan was to get the rear ironed out and then deal with the front next.

As for if the rears are facing the correct way, the shims on the Jeep when I got it had the fat side forward so I assumed that was the correct orientation. It feels like if they were the other way the pinion would be facing down.


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post #12 of 86 Old 03-10-2020, 07:18 PM
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Having just been through this recently, I definitely have an opinion. I purchased my CJ5 with a lift already on it. The driveshaft angles were never addressed properly and I took it on what ended up being a very expensive vacation. I dont enjoy spending money willy nilly like, but I definitely approve of the Tom Woods CV shaft. Its a few hundred dollars that you're likely not going to have to spend again on the rear driveshaft. After installing my CV driveshaft, the thing ran down the road like butter and still does. The guys are great and will talk you through all the phases of it.

Here's my thread on it: https://www.jeepforum.com/forum/f8/d...story-4356925/

Theres also another thread of mine from when I first joined the forum trying to diagnose a driveline vibration and doing every tweak and mod I could muster up to stop it. Until it eventually failed. Epicly.
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post #13 of 86 Old 03-10-2020, 07:32 PM
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Quote:
Originally Posted by PottsyCJ5 View Post
Great feedback. I really appreciate it. It would be a hell of a lot easier to go the driveshaft route. Iím not crazy about the cost but will be pretty frustrated if I go to the effort to remove the shims and still end up having issues. Itís sounding like even if removing the shims improves things I might be better off overall with the CV shaft. If thatís the case, Iím leaning towards just doing it and gaining the added benefits of things being super smooth and trouble free.

If I go the CV drive shaft route, any idea if the Dana 20 on a 75 would have a 10 or 26 spline yoke?

Is it a complicated job replacing the yoke with the SYE on the Dana 20? That seems like the only tricky part. Is it just bolt on for the most part?

The front springs didnít come with shims and the pinion up front still looks close to parallel to the floor. I havenít had it in 4-wheel yet after the accident. My plan was to get the rear ironed out and then deal with the front next.

As for if the rears are facing the correct way, the shims on the Jeep when I got it had the fat side forward so I assumed that was the correct orientation. It feels like if they were the other way the pinion would be facing down.
Fair enough...may be best to go shaft in a CJ5. Dunno. Just trying to save you bucks you possibly don't need spend. Did you check with the manufacturer about the shims?
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post #14 of 86 Old 03-10-2020, 08:11 PM
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You have two choices, and both have been suggested.

Your pictures clearly show that the angled shim on your new springs are pointing the pinion shaft towards your TC output shaft. If you want to run it that way you will need a double cardan (CV) driveshaft as in the top diagram.

If you remove the angled shim and point the pinion shaft forward, so it is close to parallel with the TC output shaft, Like the lower diagram, you can use a conventional two joint driveshaft.

Replace the U joints, there shouldn’t be any slop in a U joint, buy quality U joints, they last longer with less failure rate.

Check the attached diagram.
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post #15 of 86 Old 03-11-2020, 05:56 AM Thread Starter
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That is a crazy story and a good read. Thanks for sharing, I think Iím convinced. Thatís exactly the kind of issue I donít want to have - I have some long trips planned for this summer.

I took some measurements last night and Iím gonna call tom woods today. I really appreciate the fellas trying to help me save a few bucks, under most circumstances I would try to make it work and try your suggestions. But ultimately the decision comes down to having just put about 150 hours and about 3k into getting the Jeep back on the road, and needing to just get this right (I also want to avoid damaging my diff or TC). It also sounds like I will have the highest chance of a super smooth setup going with the Double Cardan. I feel more comfortable going forward with that in mind, as opposed to it should be ok at the angles Iíd be running. I want this thing as butter smooth as possible.

Iím gonna have to take a look at my angles and make sure the shims currently installed are correct and the rear diff is pointed directly at the TC output. Iím hoping I donít have to change the shims out as well to do this. If I understand correctly the new yoke for the double Cardan setup is going to be longer, so the diff may still need to come up a couple of degrees. Eyeballing it seems like it might be close as is though.

Being a 75í it also sounds like my rear diff is intended to be offset from the factory and it looks like it is. But from what I read here it sounds like the double Cardan will still work.

Iíll address the front after I get this ironed out but for now my hope is it will work as is.

If anyone knows if I have a 10 or 26 spline yoke on my OEM Dana 20 from 75í I would appreciate it. Just trying to get this thing ordered and wonít have time for a few days to get the driveshaft dropped.

Quote:
Originally Posted by MrButterfield View Post
Having just been through this recently, I definitely have an opinion. I purchased my CJ5 with a lift already on it. The driveshaft angles were never addressed properly and I took it on what ended up being a very expensive vacation. I dont enjoy spending money willy nilly like, but I definitely approve of the Tom Woods CV shaft. Its a few hundred dollars that you're likely not going to have to spend again on the rear driveshaft. After installing my CV driveshaft, the thing ran down the road like butter and still does. The guys are great and will talk you through all the phases of it.



Here's my thread on it: https://www.jeepforum.com/forum/f8/d...story-4356925/



Theres also another thread of mine from when I first joined the forum trying to diagnose a driveline vibration and doing every tweak and mod I could muster up to stop it. Until it eventually failed. Epicly.

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