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Discussion Starter #1
For the life of me I can't figure out why this is so confusing. In the middle of doing some repairs to the Jeep (again) and I got to thinking about the lift. I know I need a longer driveshaft for a 4" lift vs a 2.5" but I can't make my mind understand the SYE. A slight learning disability makes imagining how things work difficult but once I have something in hand I can usually "see" it. I just can't afford to order a driveshaft and a SYE so I can look at them side by side to decide. To be clear.... do I need a longer driveshaft or a SYE with a 4" lift or are they the same darn part?

Sorry for the stupidity mid-week.

RichnSteph
 

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It’s in the name-slip yoke eliminator. The tail piece of the transfer case has the yoke which the driveshaft BOLTS to. On a stock setup there is simply a shaft coming out of the transfer case where the driveshaft slips onto or off of. SYE with proper driveshaft the slip is built into it.


1992, 4.0,5 spd, BDS 4.5 heavy duty lift, jb conversions ss sye, 8.8 with ARB, Aussie front, tj shafts, dual dia.brake booster, 33” bfg a/t
 

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The stock transfer case has the slip yoke built into the rear of the transfer case. So when the suspension travels the driveshaft and get a little shorter or longer. The driveshaft is solid it has no slip yoke to allow for movement.


stock driveshaft with no slip



A slip yoke eliminator eliminates the slip yoke on the transfer case and makes the shaft much beefier and shorter allowing for a longer driveshaft. And since the yoke is fixed it allows you to use a CV shaft to help fix driveshaft angles. The CV driveshaft has 3 u-joints on it and a slip yoke in the middle allowing for movement of the suspension.



CV shaft with the slip yoke




You can not run a CV shaft on a np231 without a slip yoke eliminator
 
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The stock transfer case has the slip yoke built into the rear of the transfer case. So when the suspension travels the driveshaft and get a little shorter or longer. The driveshaft is solid it has no slip yoke to allow for movement.


stock driveshaft with no slip



A slip yoke eliminator eliminates the slip yoke on the transfer case and makes the shaft much beefier and shorter allowing for a longer driveshaft. And since the yoke is fixed it allows you to use a CV shaft to help fix driveshaft angles. The CV driveshaft has 3 u-joints on it and a slip yoke in the middle allowing for movement of the suspension.



CV shaft with the slip yoke




You can not run a CV shaft on a np231 without a slip yoke eliminator

Agallochs pics are great examples of each shaft, but they are pointing in opposite directions, the big black thing on the rt side of pic 2 actually bolts to the transfer case output with a different yoke installed. The double u-joint on it allows a smoother transfer of power and allows a sharper driveshaft angle, If it helps to get into your head a little easier. The axle gets shimmed at the springs to match the driveshaft when you install the taller springs.
 

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Discussion Starter #5
Ok. So to keep vibrations down and correct angles on a 4" lift I need the thing in picture number 2. Along with the lift of course.

Thanks folks!

RichnSteph
 

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Ok. So to keep vibrations down and correct angles on a 4" lift I need the thing in picture number 2. Along with the lift of course.

Thanks folks!

RichnSteph



lol oh no a SYE is a lot of work.



You need a Slip Yoke Eliminator thats about $300. You also need a double cardan CV driveshaft another $300. You also need to cut and rotate your axle perches to get the pinion yoke at a steeper angle. That requires a welder or someone who has one.
 

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Agalloch, correct me if I'm wrong, but he should be ok with a 2.5" lift on the cut and welding of his axle perches?

If he's thinking 4" lift we're getting into gearing to fit the big ass tires he will want to run, and that's a whole dozen new Threads...LOL
 
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OR you can run a transfer case drop...
I've been running a 1" drop for many years w 4.5" lift... no vibes even at 100 mph
 

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Discussion Starter #9
LOL! You kill me GIAL.

Rotating the axle isn't an issue, it wouldn't be the first time that I've relocated perches or knuckles. Gearing isn't an issue as I'm smart enough to pay someone else to do the install and have access to Google to determine the correct ratio. :) 33's are as large as I'll go on this one. The kit I'm buying has a 1" TC drop along with all the other little nit-noid thingies like shims for the axle so I'm most likely not going to have to cut/weld but can do so.

The only real issue is that I no longer own a welder and even if I did I don't have a serious place to do this until I get my garage cleaned out (AKA throw out all this crap that we don't need anymore). Most of the little stuff I can do in the street in front of the house just as long as the HOA Nazi doesn't drive by. :(

Thanks folks! You keep it interesting.

RichnSteph
 

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LOL! You kill me GIAL.

Rotating the axle isn't an issue, it wouldn't be the first time that I've relocated perches or knuckles. Gearing isn't an issue as I'm smart enough to pay someone else to do the install and have access to Google to determine the correct ratio.
33's are as large as I'll go on this one. The kit I'm buying has a 1" TC drop along with all the other little nit-noid thingies like shims for the axle so I'm most likely not going to have to cut/weld but can do so.

The only real issue is that I no longer own a welder and even if I did I don't have a serious place to do this until I get my garage cleaned out (AKA throw out all this crap that we don't need anymore). Most of the little stuff I can do in the street in front of the house just as long as the HOA Nazi doesn't drive by.


Thanks folks! You keep it interesting.

RichnSteph
I just installed a 4” Rubicon Express and I skipped the TC drop kit because I have already installed a SYE. I paid $170 for the SYE kit and it retained the mechanical speed gear. I’m told the TC drop is to accommodate the slip yoke in a stock setup. You shouldn’t have to rotate the axle for a 4” lift and your lift will likely come with bolt on shock relocation brackets anyway.

You definitely want to get a SYE. They’re relatively easy to install as long as you pay attention. I paid $170 because my kit didn’t come with a chain. I ended up replacing the chain after all so the true cost was closer to $250.

I’ll attach a pic of my NP231 that Grenaded with a slip yoke and a 2.5” lift. Look close.
 

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