Topic: Is a sye & drive shaft needed for 4" lift on a TJ ???

[BOOGIE444]

I plan on going with a rough country 4" lift, it comes with a transfer case lowering kit do I still need a sye & new longer rear driveshaft to avoid drivetrain vibrations and problems???  Oh and the lift is for a TJ.

Sorry for another newb quesiton......

[Jeffy]

Not right away but if you want to remove that transfer case spacer you will need one.  Well that really depends on how much offroading you plan on doing.  If it's little to none then you should be ok with just the shims.  Still it's best to do it right and get the SYE.

[BOOGIE444]

I dont mind having the transfer case shims in there, I just dont want the drivetrain to shake itself apart.  So when you install a sye a longer driveshaft is req's right?  You cant just put a sye in by itself?

[Jeffy]

I dont mind having the transfer case shims in there, I just dont want the drivetrain to shake itself apart.  So when you install a sye a longer driveshaft is req's right?  You cant just put a sye in by itself?

No, you need a new driveshaft.  The stock one will not long work.  Not only is it not long enough but it you're also moving from a slip-yoke to a standard U-joint. (or double U-joint aka: double cardon/CV)

If you go offroad then you will want to have the SYE.

[BOOGIE444]

Why do you feel a sye and driveshaft is necessary for offroad but no so much for on road?

[lanulos89]

bc on road you dont flex much and the angle of the shaft dont change much.  off road the angle changes numerous amounts of times.  plus if you blow apart you rear axle, you can simply unbgolt your driveshaft and drive home.  w/o the sye you can't rlly drive w/o pluging the hole in the tcase., or you will loose all your fluid.

[Jeffy]

Why do you feel a sye and driveshaft is necessary for offroad but no so much for on road?

First off you're raising the jeep 4" but you're only lowering the transfer case 1".  This brings the driveshaft out of phase which can cause vibrations.  You can get cam'ed control arms bolts to help move the pinion back into phase though.  The angle is still fairly steep even with shims.  This means the U-joints will be doing more work and wear out faster then normal.  When you're on road, the axle moves very little.  When you're off road it moves a lot more.  Mostly twisting but also some compressing and extensions as well.  With the stock driveshaft you lose that 1" of ground clearance because of the shims.  You also risk having the driveshaft fall out when the suspension is in extension.  Worst case the driveshaft will slide out as you're putting the power on and it cracks the slip yoke or twists the splines.  The slip yokes don't have that much slip built into them.  With the lift, there will be more shaft exposed since there is a greater distance to cover.  When the driveshaft is removed, a 2" hole is exposed and if left unplugged, it will leak badly.

[BOOGIE444]

Thanks guys, I actually understand why a sye is needed, other than just because quadratec says so.

[BOOGIE444]

Looks like I better skip the locker / limited slip idea and put that cash towards a sye & driveshaft.

[BOOGIE444]

Well if I am going to stick the money in a sye and driveshaft might as well stick a 1" coil spring spacer in there to get 5" of lift, or does this change other stuff too.

[aw12345]

There are several cases to be made for a sye and cv shaft the biggest is when lifting the drive shaft could end up being to short. Now on TJ's removing the rear shaft does not cause an oil leak like a TJ however the stock output shaft is very skinny and can break and will cause an oil leak a SYE addresses this problem with a thicker shaft.
You could lift it 5" if you want with a SYE and cv shaft

[cmgorman94]

There are several cases to be made for a sye and cv shaft the biggest is when lifting the drive shaft could end up being to short. Now on TJ's removing the rear shaft does not cause an oil leak like a TJ however the stock output shaft is very skinny and can break and will cause an oil leak a SYE addresses this problem with a thicker shaft.
You could lift it 5" if you want with a SYE and cv shaft

What? Does anyone know what that babble means?  What size tires do you want to run with 5" of lift? For 33s you definitely won't need that much, and I wouldn't do it. That's just my opinion though.  The less lift you can run for the tire size the happier and more stable you'll be.

[Bounty Hunter]

5" is a lot of height for a short-arm type lift, will cause lots of problems offroad and on.  Like mentioned above, use as little lift as possible to clear your desired tire height.  A 3" or 3.5" kit works well with a 1" body lift.

You can get a good SYE for as low as $180, and I recommend getting a used TJ or XJ front driveshaft and having it shortened for use in the rear with the SYE.  Save you a lot of $$.

[BOOGIE444]

Ok, I will stick with 4" lift, and if it looks to wimpy I will stick a 1" body lift on it at a later time.  Where do they sell sye for $180?  The lowest I seen is on quadratec for $219.00.

[Bounty Hunter]

http://www.performanceoffroadcenter.com/oscommerce/product_info.php?products_id=153

I've installed about a 1/2 dozen of these kits.