The Official SYE (Slip Yoke Eliminator) Thread

Alright well that saves me a lot of time and money. I'm glad I found this thread then. I guess I'll research more on the difference between driveshaft vibrations and the death wobble, but this helps a lot.
 
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I went with Adams Drive Shaft and AA SYE; very happy with my purchase and the customer service they provide me, including REAL fast shipping service!

My death wobble issue was also the result of bad tires: 1.) they were over inflated by the PO and I failed to check them.. 2.) the tread was also de-laminating from the tire, cause in to be out of balance; put on a new pair of treads and I was good to go! I also made sure the the entire steering system nuts/bolts were tighten down to spec and installed a new steering stabilizer too... just for a small sense of security.....
 
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I went with Adams Drive Shaft and AA SYE; very happy with my purchase and the customer service they provide me, including REAL fast shipping service!

My death wobble issue was also the result of bad tires: 1.) they were over inflated by the PO and I failed to check them.. 2.) the tread was also de-laminating from the tire, cause in to be out of balance; put on a new pair of treads and I was good to go! I also made sure the the entire steering system nuts/bolts were tighten down to spec and installed a new steering stabilizer too... just for a small sense of security.....

Yep, it seems like the majority of time, people spend so much time and money chasing down the death wobble, and it turns out to be the simplest solution, the tires!
 
I only have a 2" lift, and I don't want to drop the cash on an SYE and CV drive shaft.

However, I am interested in reducing any possible wear on my transfer case, especially whenever you're suspension is flexing; as I understand it, a fixed yoke reduces leverage on your transfer case output shaft? And, a CV drive shaft returns your axle to its factory angle? Or - do you also need adjustable control arms to get your rear axle, at the very least, back to its factory angle?

On a separate note, I do indeed have issues with my rear bump stops not contacting completely parallel to my spring perches. I believe this is due to my 2" lift and stock driveshaft?


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On a separate note, I do indeed have issues with my rear bump stops not contacting completely parallel to my spring perches. I believe this is due to my 2" lift and stock driveshaft?

This is due to lifting the vehicle and the need to install spring perch relocation brackets to make things parallel again. It's not a 100% must, but if you want it to be the way you describe, you'll need to relocate the spring perches.
 
This is due to lifting the vehicle and the need to install spring perch relocation brackets to make things parallel again. It's not a 100% must, but if you want it to be the way you describe, you'll need to relocate the spring perches.

Understood. But, what if I got a SYE and a CV shaft? Would that solve it too?
 
This thread is designed for the sole purpose of informing members as to why it is important to put a SYE on your lifted Jeep Wrangler. Now we can answer the “Do I need a SYE” questions by simply pointing people to this thread. I hope this thread will help new members make the right choice when installing a lift on there TJ.

What are Slip Yoke Eliminators and why should they be used?

What is a SYE and why is it used?
SYE stands for Slip Yoke Eliminator. The Slip yoke is the yoke that slides over the output shaft of the transfer case. This is the yoke that the rear driveshaft connects to at the Transfer case.

The SYE kit replaces the stock slip yoke and housing with a sealed housing and a fixed flange or yoke. This fixed flange or yoke is what a new CV style driveshaft will bolt up to. A CV (constant Velocity) shaft uses two U joints instead of a single one and this allows for much steeper angles. These shafts also utilize a two piece design that allows for suspension travel by allowing the shaft itself to compress and extend verses the yoke sliding on the output shaft. The sealed output now also allows for the rear driveshaft to be removed from the vehicle and not allow the transfer case fluid to empty out of the transfer case.

When should a SYE be used?
The stock rear driveshaft is a fixed length unit that relies on the slip yoke to adjust when the suspension travel. When lifting an TJ, the angle between the rear axle pinion and the slip yoke become much greater. The factory setup was not intended for these variations in lift. The angle difference will be most noticeable in the fact the slip yoke will be pulled further out of the housing than before the lift.

The differences in angle can be attributed to several things, but they all revolve around this center point, the length of the rear driveshaft. You will hear various things from various people about what size lift can be ran without a SYE. The key here is to recognize the differences between their TJ and yours.

What are some of the harmful effects of not using a SYE?
The difference in the angles put a strain on the output shaft. This places load on the transfer case bearings and the seals on the output shaft.

Another, more obvious problem, are the U joint ears of the driveshaft making contact with the slip yoke as the driveshaft spins. This will make for a noticeable clanking noise and hard vibration. A transfer case drop will clear that problem up, as well as a high clearance extended slip yoke, but it will not correct the strain on the output shaft.

What are other positives does the use of a SYE provide?
As mentioned before the ability to remove the rear driveshaft if damaged and drive off a trail under the power of the front axle is a major plus. If you run a stock front driveshaft with a SYE, you can carry a spare for both the front and the rear driveshafts.

Hack N/ Tap vs. SYE
There are two different styles of SYE’s out there. There is the HD Slip Yoke Eliminator, and then there is the Hack N’ Tap. The two are relatively different but the end result is going to be relatively the same. With the HD SYE the output shaft inside the transfer case is actually going to be replaced making the SYE the stronger of the two options. With the Hack N’ Tap you actually cut the OEM output shaft then add a flange on it which will then connect to the new CV driveshaft.

In summary, a true SYE is going to be a better option versus the Hack N' Tap. However, if you are on a budget a Hack N' Tap will certainly get the job done.

Rear Shocks
After adding a SYE you may encounter some rear shock issues (especially if you're lifting it over 2 inches). When you rotate the pinion up to match the transfer case output yoke, the lower portion of the shock body may rub on the lower spring perch.

The cheap and easy way to fix it are these Currie CE-9601 Rear Lower Shock Mount Extensions.

The proper way (in my opinion) to fix it, is to relocate your spring perches using something like this. This will of course require a competent welder, but it's really not that hard of a job.

Which SYE do you recommend?
If you're fortunate enough to have the NP241OR Rock-Trac transfer case (only found in the 03-06 TJ and LJ Rubicon models) then you don't need a SYE, since this transfer case already has one from the factory.

If you're like the majority of us however and have the NP231 transfer case as found in all the other TJ and LJ Wrangler models, there are various options in regards to SYE kits, but one of the most popular and well regarded is the Advanced Adapters SYE.

There's certainly a lot of other options out there which I won't even begin to list, but the Advanced Adapters SYE is my favorite.
So for my own sanity... I have 3” SL and stock driveshaft with no vibrations. Other than to correct the driveline/pinion angle, why would I want one? Just curious.
 
So for my own sanity... I have 3” SL and stock driveshaft with no vibrations. Other than to correct the driveline/pinion angle, why would I want one? Just curious.

No transfer case drop or anything either? If that's the case, I'm shocked you don't have vibrations!

When you start getting over 2" of lift, typically you add a SYE. When you do that, you need to add a CV style driveshaft because the stock driveshaft won't work with the SYE properly. Without an SYE and CV driveshaft, it's not going to be able to achieve the angles that you could otherwise.

As you lift your vehicle, you begin to need a longer driveshaft. My guess is that your driveshaft you've got on there is barely long enough, and it's likely at the very end of it's travel on the slip joint.

It would be easy to tell with pictures of course. Now if you have a transfer case drop, that's a different story, because then your stock driveshaft will work just fine.
 
No transfer case drop or anything either? If that's the case, I'm shocked you don't have vibrations!

When you start getting over 2" of lift, typically you add a SYE. When you do that, you need to add a CV style driveshaft because the stock driveshaft won't work with the SYE properly. Without an SYE and CV driveshaft, it's not going to be able to achieve the angles that you could otherwise.

As you lift your vehicle, you begin to need a longer driveshaft. My guess is that your driveshaft you've got on there is barely long enough, and it's likely at the very end of it's travel on the slip joint.

It would be easy to tell with pictures of course. Now if you have a transfer case drop, that's a different story, because then your stock driveshaft will work just fine.
No tcase drop or anything lol. It probably is on the last leg of its travel distance though.
 
No tcase drop or anything lol. It probably is on the last leg of its travel distance though.

Holy cow... Usually at 2" or more you need a transfer case drop or SYE / CV driveshaft. If not, you'll experience vibrations. Not to say it's not possible, it's just very uncommon!
 
I'm trying to understand the geometry the our suspensions - what if I had control arms for a 2" lift and a SYE and CV drive shaft? Wouldn't that push the axle back to original spec?

This is what you should read:
What is a SYE/CV driveshaft and why do I want one?

That explains all of it in great detail.

But to answer your question, no, if you had all of that, it wouldn't change your axle back to stock specs. For one, your spring perches would still be off from parallel (unless you got perch relocation kits), and your pinion angle is now always going to be pointing more upwards than it would if you had a conventional two joint driveshaft like this:

2joint_angle.gif


With the SYE and CV driveshaft, you'd never be able to achieve that angle... ever. Your pinion is always going to be pointing upwards at almost the same angle as the driveshaft.

Read that thread though, it's very detailed, and it goes into depth.
 
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Hi Folks,
3.5” Metalcloak lift going on soon with BFG 285/70/17’s.

Who can provide me with what to buy? Looking for SYE and CV.

Not going cheap either so spare no expense.

Thanks everyone
 
Hi Folks,
3.5” Metalcloak lift going on soon with BFG 285/70/17’s.

Who can provide me with what to buy? Looking for SYE and CV.

Not going cheap either so spare no expense.

Thanks everyone

The first five posts of this thread have the information that you are looking for.
 
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Hi Folks,
3.5” Metalcloak lift going on soon with BFG 285/70/17’s.

Who can provide me with what to buy? Looking for SYE and CV.

Not going cheap either so spare no expense.

Thanks everyone

Call up Tom Wood:
http://www.4xshaft.com

You'll need a new driveshaft and a SYE. He can sell you both as a kit if you tell him what make and model your Jeep is, how much you're lifting it, etc. Tom Wood is one of the best. I order all my driveshafts from him.

Super fast shipping and turn around time too!
 
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The first five posts of this thread have the information that you are looking for.
Just received my Advanced SYE and Adams Driveshaft.... this set up looks sweet! $470 out the door with a t-shirt. Customer Service was great as well.

Last question... what brand of transfer case chain do you guys recommend?

Figure I replace the chain while they are in there. No problems now with stock TJ Sahara but never know once I toss on the 3.5 MC lift.

Thanks!