i see a lot of stuff in here about a SYE, I am going to be doing a 4 inch lift on my 96 xj sport, and i planned on lowering the transfer case, but i am wondering what this sye is, if someone could explain, and also whatever it is, if i need to do one when i do my lift, thanks a lot
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what is a SYE
- Thread starter 96blackxj
- Start date
Dirk Funk
NAXJA Forum User
- Location
- Lexington, Ky
SYE stands for slip yoke eliminator. The transfer case on your jeep has a slip yoke on the output shaft. It allows the length between the transfer case and the rear axle to fluxuate as the rear axle oscillates up and down while hitting bumps etc. The slip yoke is some spline on the driveshaft that "slips" in and out of a sleeved output shaft on your transfer case.
This design works well on a stock vehicle, but when the jeep is raised with a lift, the angles between the transfer case and the rear axle are increased. This puts stress on the U-joints and may cuase driveline vibrations. It also puts stress on the output bearings on the transfer case. Not only that, but as the jeep is raised more spline is pulled out of the sleeve because with a lift, the driveshaft now needs to be longer. It is possible for the spline to fall all the way out.
An SYE has two purposes: to reduce the angle between the transfer case and the rear driveshaft by reducing the length of the transfer case, and to create a fixed yoke output so that a double cardigan, constant velocity driveshaft can be used. An SYE includes a new tailshaft housing which is significantly shorter than stock and this makes your transfer case around 6" shorter with a fixed yoke. Then you run a new longer driveshaft with slip spline in the middle of it. This new driveshaft also has more U-joints which soak up the angle they need to accomidate.
One last point. An SYE includes a new transfer case main shaft which is MUCH beefier than stock. This reduces your chances of breaking the main shaft under heavy torque loads.
Once all this is done, you are left with a relatively bomb proof transfer case and no driveline vibes. I hope this helps.
This design works well on a stock vehicle, but when the jeep is raised with a lift, the angles between the transfer case and the rear axle are increased. This puts stress on the U-joints and may cuase driveline vibrations. It also puts stress on the output bearings on the transfer case. Not only that, but as the jeep is raised more spline is pulled out of the sleeve because with a lift, the driveshaft now needs to be longer. It is possible for the spline to fall all the way out.
An SYE has two purposes: to reduce the angle between the transfer case and the rear driveshaft by reducing the length of the transfer case, and to create a fixed yoke output so that a double cardigan, constant velocity driveshaft can be used. An SYE includes a new tailshaft housing which is significantly shorter than stock and this makes your transfer case around 6" shorter with a fixed yoke. Then you run a new longer driveshaft with slip spline in the middle of it. This new driveshaft also has more U-joints which soak up the angle they need to accomidate.
One last point. An SYE includes a new transfer case main shaft which is MUCH beefier than stock. This reduces your chances of breaking the main shaft under heavy torque loads.
Once all this is done, you are left with a relatively bomb proof transfer case and no driveline vibes. I hope this helps.
- Location
- Terra Firma
SYE = Slip Yoke Eliminator. More properly should be called "short shaft" adapter, but SYE has become the accepted acronym.
Take a look at your transfer case and you'll see that the front output has a short output shaft with a fixed yoke, and the slip joint is in the drive shaft. The rear, however, has a slip spline on the output shaft, which results in a relatively long unsupported length of shaft hanging out there. The SYE basically replaces the transfer case tail cone with a shorter housing and a fixed yoke, like the front output, and then you modify or replace the driveshaft to put the slip spline in the drive shaft where it should have been from the factory.
Take a look at your transfer case and you'll see that the front output has a short output shaft with a fixed yoke, and the slip joint is in the drive shaft. The rear, however, has a slip spline on the output shaft, which results in a relatively long unsupported length of shaft hanging out there. The SYE basically replaces the transfer case tail cone with a shorter housing and a fixed yoke, like the front output, and then you modify or replace the driveshaft to put the slip spline in the drive shaft where it should have been from the factory.
CheapXJ
NAXJA Forum User
- Location
- 570, 813 or 303
STRYKER
NAXJA Forum User
- Location
- Leesburg, Va
96blackxj said:
If you read the supplied info in the link that CheapXJ offered (I'm the author
), you'll see that your XJ should have come from the factory equipped with the equivalent of a SYE.... and I honestly believe that if Renault hadn't been calling the shots at the time, that it would have recieved one....It is my opinion that EVERY XJ of no - or any - lift needs the SYE to balance out the driveline to the rear. Some 1997-2001 XJ's came from the factory with vibrations... a clear sign that Chryco and DCX are also to stingy to fix a design defect.
CaptTrev
NAXJA Forum User
- Location
- Long Island
96blackxj---
to specifically answer your question about your 96 XJ.
(the others answers were fantastic, but didnt address YOUR specific question)
i have a 96 XJ (also black ) with approx 4-5" of lift, and i dropped the transfer-case 1" with stainless nuts as spacers (cheapest vib-eliminator at the time) ...and this got rid of a lot of vibs. my jeep is very driveable now...hardly even notice the little vibs i DO have at certain speeds.
i AM going to throw in a SYE in the future, either A)-when i get more $
and/or B) when i go with a bigger lift (would love a 8" lift)
so,
lift it.
drop it (x-fer case)
and drive it.
if u can deal with the minimal vibs, then i say wait and spend $ on other things.
CaptTrev
to specifically answer your question about your 96 XJ.
(the others answers were fantastic, but didnt address YOUR specific question)
i have a 96 XJ (also black
) with approx 4-5" of lift, and i dropped the transfer-case 1" with stainless nuts as spacers (cheapest vib-eliminator at the time) ...and this got rid of a lot of vibs. my jeep is very driveable now...hardly even notice the little vibs i DO have at certain speeds. i AM going to throw in a SYE in the future, either A)-when i get more $
and/or B) when i go with a bigger lift (would love a 8" lift)
so,
lift it.
drop it (x-fer case)
and drive it.
if u can deal with the minimal vibs, then i say wait and spend $ on other things.
CaptTrev
STRYKER
NAXJA Forum User
- Location
- Leesburg, Va
CaptTrev said:96blackxj---
to specifically answer your question about your 96 XJ.
(the others answers were fantastic, but didnt address YOUR specific question)
i have a 96 XJ (also black
i AM going to throw in a SYE in the future, either A)-when i get more $
and/or B) when i go with a bigger lift (would love a 8" lift)
so,
lift it.
drop it (x-fer case)
and drive it.
if u can deal with the minimal vibs, then i say wait and spend $ on other things.
CaptTrev
A. I did address it. lowering the transfer case is....
Well, I'm desperately trying to be nice.
As well as another post on this forum about it altering the front driveline in the exact reverse of what is done out back.
B. The article will explain that vibrations or the lack of them are not your concern. Runout is. Lowering a TC does not stop runout.
- Location
- Indiana-Missouri
Danpaps
NAXJA Forum User
- Location
- Bergen Co, NJ
Hey blackxj, What size tires you gunna put on that, I have Vibes. 4.5 inch with tran case drop, but since i only have 31's the shaft was on a steaper angle then my friend who ran 32's with the same lift and i got vibes and he didn't so you might want to stick it out with the 32's and avoid the SYE kit if possible-they can be harsh on the wallet
dave
NAXJA Forum User
- Location
- dirty Joisey
honestly,
i've tackled this problem both ways. here is my opinion. when you put an SYE in you are combatting a couple issues.
1. driveline vibes - can be fized with shims / tcase drop
2. travel - how far can you droop without the driveshaft falling out
3. - strength - there are added forces when using bigger tires/ different gears/ lockers
1 is easy enought o solve cheaply. 2 and 3 need to be addressed with an sye. i personally regret ever wasting time and money trying to cheapskate my way around vibes.. i came very close to losing a driveshaft that way. go with an SYE . it is one of the best investments you can make.
i've tackled this problem both ways. here is my opinion. when you put an SYE in you are combatting a couple issues.
1. driveline vibes - can be fized with shims / tcase drop
2. travel - how far can you droop without the driveshaft falling out
3. - strength - there are added forces when using bigger tires/ different gears/ lockers
1 is easy enought o solve cheaply. 2 and 3 need to be addressed with an sye. i personally regret ever wasting time and money trying to cheapskate my way around vibes.. i came very close to losing a driveshaft that way. go with an SYE . it is one of the best investments you can make.
RCP Phx
NAXJA Forum User
- Location
- Phoenix,Az
Danpaps said:
Tire size does not change the angles.It will reduce shaft speed so that could have been the difference!
