ThomasFletch

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From what I have read on the forum here, the 2.5” lift can cause vibes and varies from TJ to TJ. The problem I am currently having is a shudder/vibration that lasts only a second from a hard acceleration. Smooth acceleration appears to be fine. That being said, I am 90% sure that my issue will be resolved with a SYE and CV/DC Driveshaft install. My theory is that since the angle difference is so small that when accelerating hard, the resulting torque twists the rear axle slightly, causing the momentary shudder. For reference, I have:

OME 2” HD lift kit (Which I have read on here is actually 2.5”)

— 1.25 Savvy Body lift

— 1" JKS Aluminum Motor Mounts

— 33" BFG K02s

— 5.13 Gearing

I would rather spend the money on a SYE install than do a Tcase drop, but what do you guys think? Would not doing this cause any damage long term?
 

TheBoogieman

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I've never had any TJ with a lift that small, a MML and vibes. Any vibes are bad, so I guess you need the SYE.
p.s. Personally, I'd rather spend $6 at Lowe's for thick washers, then a SYE and driveshaft to accomplish the same thing. Dropping the skid 1/2" isn't noticeable, unless your OCD meds aren't working.
 
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97TJNM

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I'd agree with Boogie. Whatever is causing your vibes, you want to find and fix.

If it was me, I'd buy $20 worth of washers and temporarily drop the t-case, to see if that fixed the vibe. If it did, I'd then order a SYE and run it with the washers until I got the SYE in and had an afternoon to install it. That way I could diagnose the vibe for sure before dropping the cash on a SYE, temporarily fix my vibes until I got the SYE, and when it was all said and done, I'd have some more washers for the bolts bucket.🤣
 

freedom_in_4low

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Edit: Ignore the following, I just noticed you have JKS motor mount spacers. A SYE and DC driveshaft is not needed for that small of a lift. I'd temporarily, as recommended above, stack enough washers around the six transfer case bolts between the frame and skid plate to lower it 5/8" to 3/4" which will stop the vibrations.

I'd then install a pair of 1" "Bombproof" motor mount lifts with rubber (not polyurethane) bushing from https://mountainoffroad.com/collect...f-motor-mount-kit-for-1-lift-97-06-yj-tj-lj-1 and then remove the washers from the skid plate to raise it back up to the factory position.

The 1" motor mount lift works like the transfer case skid plate spacers do to remove the vibrations by eliminating the excessive angles at the rear driveshaft caused by the suspension lift but without the resulting loss of ground clearance. Plus it gives the oil pan more ground clearance, a good thing.

He already has a jks 1" motor mount lift, with presumably factory mounts.


To the OP, it'll be better to just do some diagnosis before loading up the parts cannon. Get a magnetic digital angle finder and measure the angles of your pinion, transfer case, and the main tube of the shaft.
 

freedom_in_4low

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Haha @Jerry Bransford I don't know if your edit went through in the instant I hit the reply button or if ninja moderator abilities were involved but the edit was not there when I read it the first time.
 
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ThomasFletch

ThomasFletch

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To the OP, it'll be better to just do some diagnosis before loading up the parts cannon. Get a magnetic digital angle finder and measure the angles of your pinion, transfer case, and the main tube of the shaft.
Is there any brand or specific model I should look at? I did take off the rear driveshaft and tried to re-create it, but the front tires couldn't generate enough grip to pull hard enough, I think.

I'd agree with Boogie. Whatever is causing your vibes, you want to find and fix.

If it was me, I'd buy $20 worth of washers and temporarily drop the t-case, to see if that fixed the vibe. If it did, I'd then order a SYE and run it with the washers until I got the SYE in and had an afternoon to install it. That way I could diagnose the vibe for sure before dropping the cash on a SYE, temporarily fix my vibes until I got the SYE, and when it was all said and done, I'd have some more washers for the bolts bucket.🤣
I've never had any TJ with a lift that small, a MML and vibes. Any vibes are bad, so I guess you need the SYE.
p.s. Personally, I'd rather spend $6 at Lowe's for thick washers, then a SYE and driveshaft to accomplish the same thing. Dropping the skid 1/2" isn't noticeable, unless your OCD meds aren't working.
I know washers are the better option money wise here, but I really don't want to install them… Since my lift is small, I want to keep as much clearance as I can. But I suppose if that really is the best option out of everything than 2" lift or so isn't too bad, right? Most of the off-roading I do is fire-roads and stuff with friends, but there is the occasional what I would consider hard trail once in a while.
 

cpwolf

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I think the thought on the washers is to drop the T Case skid and if the vibes go away, you for sure know that’s the issue. Then tou can go the SYE route.

If the vibes go away with the drip, and I agree with Boogieman, that’s not a tall lift with the MML to have vibes, not out if the question, but worth making sure

If you go the SYE route, I got the JB Conversions Super Short SYE, and a Tom Wood’s Drive Shaft.

You also have to get adjustable control arms, and an angled rear track bar bracket, and a SpeedoHealer to fix the speedometer.

So it’s not just and SYE, you may know that but I thought I’d mention it
 

97TJNM

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I think the thought on the washers is to drop the T Case skid and if the vibes go away, you for sure know that’s the issue. Then tou can go the SYE route.

If the vibes go away with the drip, and I agree with Boogieman, that’s not a tall lift with the MML to have vibes, not out if the question, but worth making sure

If you go the SYE route, I got the JB Conversions Super Short SYE, and a Tom Wood’s Drive Shaft.

You also have to get adjustable control arms, and an angled rear track bar bracket, and a SpeedoHealer to fix the speedometer.

So it’s not just and SYE, you may know that but I thought I’d mention it

This. I was just suggesting the washers as a way to check if you problem is from the rear drive shaft angle. If the washers fix your problem, then you know that you can install a sye and remove the washers and it will fix your issue. Basically it would be a cheap diagnosis, so you can determine if the sye is the way to go.
 
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ThomasFletch

ThomasFletch

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I think the thought on the washers is to drop the T Case skid and if the vibes go away, you for sure know that’s the issue. Then tou can go the SYE route.

If the vibes go away with the drip, and I agree with Boogieman, that’s not a tall lift with the MML to have vibes, not out if the question, but worth making sure

If you go the SYE route, I got the JB Conversions Super Short SYE, and a Tom Wood’s Drive Shaft.

You also have to get adjustable control arms, and an angled rear track bar bracket, and a SpeedoHealer to fix the speedometer.

So it’s not just and SYE, you may know that but I thought I’d mention it
When you say control arms, do you mean for just the rear or all around? Alo what would be the difference between SSYE and just a regular one? As for the track bar bracket, I'm pretty sure my lift already comes with one?
This. I was just suggesting the washers as a way to check if you problem is from the rear drive shaft angle. If the washers fix your problem, then you know that you can install a sye and remove the washers and it will fix your issue. Basically it would be a cheap diagnosis, so you can determine if the sye is the way to go.
Sounds like a good plan, I'll try it. I meant to tell you that with your first post I promise lol


Should I still get the angle finder?
 
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97TJNM

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When you say control arms, do you mean for just the rear or all around? Alo what would be the difference between SSYE and just a regular one? As for the track bar bracket, I'm pretty sure my lift already comes with one?

Sounds like a good plan, I'll try it. I meant to tell you that with your first post I promise lol


Should I still get the angle finder?

You'll need an angle finder if you end up installing adjustable control arms, which you will need to install if you get an SYE, so that you can dial in your driveline angle correctly.

A SYE is a Slip Yoke Eliminator, which lets you, well, eliminate the slip yoke, and run a longer driveshaft, which is nice in our Jeeps because the stock DS is so short that it doesn't take much lift before we can start introducing driveline vibrations. A SS SYE is a Super Short Slip Yoke Eliminator. It is even shorter than a standard length SYE, but requires some other parts to make things work, such as a hall effect sensor and a speedometer healer. SS SYEs generally are beneficial if you are going with more than 3.5 inches of lift. It lets you eke out a little bit longer driveshaft for those that want to run 35's.

As far as control arms go, best practice is upper and lower adjustable control arms in your situation.

Good luck!
 
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cpwolf

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When you say control arms, do you mean for just the rear or all around? Alo what would be the difference between SSYE and just a regular one? As for the track bar bracket, I'm pretty sure my lift already comes with one?

Sounds like a good plan, I'll try it. I meant to tell you that with your first post I promise lol


Should I still get the angle finder?

Someone answered perfectly, but the Super Short from JB Conversions is an excellent American Build in Louisiana. If you ever decide to go higher, you’ll be set. The SpeedoHealer as he mentioned uses the Hall effect and Digital send, and I think gets it more accurate than changing the gear speedo.

Yes, you would need control arms upper and lower adjustable for the rear. Some just do upper, I’m not a fan of that unless you’re strapped for $, and I get it, so do that and save.
 
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Hazegray

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You can buy a digital angle finder at any of the big box home improvement stores. Look online, they are usually found in the electrical section of the store...
 

freedom_in_4low

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Is there any brand or specific model I should look at? I did take off the rear driveshaft and tried to re-create it, but the front tires couldn't generate enough grip to pull hard enough, I think.

Wut.

With the rear driveshaft out, and the Jeep in 4 hi, it should have no problem driving. If it's not moving and the tires aren't resting on a frictionless plane, something else is wonky (like t case isn't getting into gear).
 

cpwolf

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Wut.

With the rear driveshaft out, and the Jeep in 4 hi, it should have no problem driving. If it's not moving and the tires aren't resting on a frictionless plane, something else is wonky (like t case isn't getting into gear).

I read that as “front tires don’t pull hard enough to recreate it the vibe” not that they didn’t pull at all.

Actually, the whole point is the vibe is gone, leads to it’s probably the rear DS angle, ha.
 

freedom_in_4low

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I read that as “front tires don’t pull hard enough to recreate it the vibe” not that they didn’t pull at all.

Actually, the whole point is the vibe is gone, leads to it’s probably the rear DS angle, ha.

Your interpretation makes more sense.

Another thing to consider is the health of the u joints. Lifting it increases the range of rotation explored btw the trunnions and the caps. I've had vibes show up after a lift just because the u joints had spent 90k miles in a little range and suddenly I was going outside of that. I could feel it when I removed the shaft because the joint would rotate nice and smooth to a point, and then gave resistance.
 

JMT

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From what I have read on the forum here, the 2.5” lift can cause vibes and varies from TJ to TJ. The problem I am currently having is a shudder/vibration that lasts only a second from a hard acceleration. Smooth acceleration appears to be fine. That being said, I am 90% sure that my issue will be resolved with a SYE and CV/DC Driveshaft install. My theory is that since the angle difference is so small that when accelerating hard, the resulting torque twists the rear axle slightly, causing the momentary shudder. For reference, I have:

OME 2” HD lift kit (Which I have read on here is actually 2.5”)

— 1.25 Savvy Body lift

— 1" JKS Aluminum Motor Mounts

— 33" BFG K02s

— 5.13 Gearing

I would rather spend the money on a SYE install than do a Tcase drop, but what do you guys think? Would not doing this cause any damage long term?

I had that shuddering vibration under load for years at 2-2.5” suspension lift. Didn’t cause any premature wear of components that I could tell. Eventually moved on to bigger lift and SYE. Smooth as glass. Now I have the same shudder on another 2” rig. I’m not worried about it.
 
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Jerry Bransford

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Keep in mind that drivetrain vibrations are usually caused by the u-joints themselves vibrating/shaking from working into an excessive angle. That type of vibration can't just be lived with as it can take out the u-joints and possibly the adjacent seals on the axle and tcase too.
 

Mike_H

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I had that shuddering vibration under load for years at 2-2.5” suspension lift. Didn’t cause any premature wear of components that I could tell. Eventually moved on to bigger lift and SYE. Smooth as glass. Now I have the same shudder on another 2” rig. I’m not worried about it.

And what, exactly is premature by your estimation?