Topic: SYE and driveshaft

[Elyod]

I have read up on SYEs and know what their purpose is, but i was wondering if anyone esle is running an sye and if so which one and how is the quality?  I was looking at the JB conversion supershort SYE.  My other question has to do with the driveshaft.  If i buy that supershort SYE or any comparable one, will i have to buy a CV driveshaft even though my driveshaft length is much longer than stock?

[lanulos89]

sye you need if you lift more than 4" 's to keep the angle of your drive shaft correct.  i dont have one so i dont know of good kits but someone will answer

[aw12345]

You can get the short adapter kit from advance adapters for 200 bucks. Your regular shaft will not work but you can get an old TJ front shaft shortend by a driveshaft place so it will fit. Or spend the bucks for a Tom Woods shaft. The whole exercise fixed my driveline vibes also you will have to aim the pinion at the transfer case Kinda like the driveshaft becomes a straight extension of the pinion yoke

Art

[Jeffy]

The SYE's out there fall into a few different categories.

• Machined 231 shafts
• Hack & Tap
• 241 32 Spline shaft

Strength wise, the machined 231 and the H&T's are about the same.  The 241 shaft is from 3/4 ton application and isn't modified so hardening isn't changed.  If you have a YJ, I would buy a modified shaft or just get a 241 shaft.  The reason bring, they charge you about a much as a modified shaft as they do for a H&T.

You really need 3" or more of lift to make a SYE worth it.  If you're stock up to 2.5" your driveshaft angles aren't that bad.  Also, with a SYE, you will need a new driveshaft.  You really want to do all this once you've finalized your suspension so you aren't paying for a driveshaft more then once.

It should be noted that doing a SYE does not mean you have to use a Double Cardon (CV) driveshaft.  If you can, a standard single U-joint setup would be better.  It's when you start lifting the Jeep higher that you'll need a CV driveshaft.

[Elyod]

This summer i plan on doing 5 1/2 inch lift.  I know i will need a SYE and a new driveshaft.  So i guess now i am wondring if i need the CV style or not.  From what i have read with the super short SYEs you don't need a CV but I never read upto what height that is still true.

[jcsanders79]

I think that you won't need a CV style shaft, the local jeep shop has told me that they get better angles out of standard style DS and they are less problematic.  I have a tera super short SYE sitting in the garage (suppose to be the shortest one out) and I should be done with everything in a few weeks and I will let you know how a standard style driveshaft works.  I have 4" of lift but I will be adding an after market belly pan that will raise the TC 2" so it will be like haveing a 6" lift which is close to what you said you will have.

[might4banger]

I have the JB standard short kit... good quality and great support.

I would stay away from a hack and tap type kit. (You cut the stock shaft down and drill and tap the yoke on.)

Also, do the whole thing - lift & SYE together or you will be changing your pinion angle 2xs.

With the tummy tuck + 4" of lift, you will have to run SYE and a custom shaft... IMO - no way the SY will have good angles.

I had a local drive line shop make me a custom DS once I finished the SYE.

[jcsanders79]

It will be a custom DS just not a CV style DS.

[jagular7]

I think that you won't need a CV style shaft, the local jeep shop has told me that they get better angles out of standard style DS and they are less problematic.  ....snip....

This is sort of a misleading statement. It all depends on the ujoint and the yoke used. The ujoint is designed to withstand torque through the use of material. The thicker the material, the larger the torque value. Then there is the cap. The cap holds the needle bearings onto the trunion. The thickness of the trunion is based on the torque value. The yoke for the ujoint is designed to hold the ujoint caps and to withstand predetermined amount of torque designed for the ujoint. (Would be pretty stupid to have a strong joint and weak yoke or other way around.) This torque is accepted through the amount of material used to hold the cap. With more material to hold a specified sized cap, the less 'angle' clearance there can be designed into the yoke for the cap and the center of the ujoint. Take a look at your steering joints on the front axle. If you were to remove the steering stops, you may hit the center of the joint onto the yoke when turning. This is why there are steering stops (not worrying about the tires interference). 
So for a given operating angle, a single ujoint has limits. However, if you want/need a great angle, doubling up ujoints splits the angle between them. Thus, the constant velocity (cv) joint would be an option. This is all relative to the setup of the particular vehicle. CVs are also designed differently. IFS has a different cv design for the axle  compared to a cv for a ds. CVs can be designed to go to greater angles and operate consistently at those angles with little problem with vibrations.
Last to mention, cvs can provide a better and smoother operation in the shafts at the operating angles.  Thus the name, constant velocity. U-joints have a problem operating at angles and this is due to the travel of the trunion.

[jcsanders79]

It should be noted that doing a SYE does not mean you have to use a Double Cardon (CV) driveshaft.  If you can, a standard single U-joint setup would be better.  It's when you start lifting the Jeep higher that you'll need a CV driveshaft.

This is what I am trying to say.  Its all about angles and if you don't need to split the angle then don't, if you do then of course you would want a CV shaft.  Most people use them because that is what the manufacture is trying to sell not because they are always needed with a SYE.  I can tell you that the Jeep shop here told me they  have done a lot of standard SYE's for Jeeps with 4" lifts and used a non CV driveshaft.

[Jeffy]

Whoops, I forgot about the Super Slim kits.  They are modified 241 shafts.  They also remove the standard VSS to a magnetic pickup.  This requires calibration done in the PCM and can't be done with a gear change anymore.  On a YJ, it would probably be better to get a self-calibrating speedometer.

[Elyod]

I have a tera super short SYE sitting in the garage (suppose to be the shortest one out) and I should be done with everything in a few weeks and I will let you know how a standard style driveshaft works.  I have 4" of lift but I will be adding an after market belly pan that will raise the TC 2" so it will be like haveing a 6" lift which is close to what you said you will have.

Great! When you get around to installing your new toys let me know how everything works.  I would like to run a standard driveshaft instead of a CV.  To get one custom made should still be less than paying 250 dollars for a CV right? 

[jcsanders79]

A used 1310 DS around here is $20-$30 and $50 to have it cut down, plus what ever new U-joints cost

[aw12345]

If using a regular style driveshat you should not use a driveline angle of more than 8 degrees as long as you stay under that you can live without a cv shaft if you go over that it will viberate as well as greatly reduced u joint life.
so with a bit of measuring you can figure this out once the belly tuck and sye is done. What to say it saves money and the single u joints are more reliable.

Art

[Elyod]

Thanks everyone.  I don't think i am doing a belly tuck, so hopefully i will have a good driveline angle.  Guess i have to wait and see.