Rear drive shaft options

[Dale]

Could someone please explain to me SIMPLY why a double cv shaft is better than a shaft with a couple of unis? Or explain the different drive shaft options

This is for use on my new Tera SYE(fitted today). Will be getting a driveshaft made Thursday just wanna make sure I get the best option.

[Phil]

From what I've been told /read/heard the cv is suposed to be slighty smoother while running and can articulate slightly better than unis but some people say the differance is minimal and going on initial cost and susequent maint / replacement unis are better.
Was the tera expensive? and is it the h/d shaft or the normal one just shorter?

[sir_camel]

I been meaning to ask for a while. I hear people talking about the SYE, well what does it actually do?

[Dale]

It's a Tera Heavy duty SYE kit. Expensive....of course it is, it's a bloody Jeep remember tongue.gif

The kit was $1100 ish and the new driveshaft is going to be about $700ish depending on how I get it set up.

The purpose of the SYE is to get rid of the poxy stock transfer case output shaft(slip yoke) set up.
What happens with the stock set up is the rear driveshaft slips long the spline on the output shaft. As a result when you start running suspension lifts with increased articulation, it starts putting all sorts of weird stresses on the output shaft and eventually it goes twang, usually just behind the speedo gear drive.The standard set up also limits lift(generally a max of 3" is all you get) as the driveline angles become to great and cause nasty vibes.
With a SYE a custom driveshaft installed the slip yoke is now on the driveshaft itself so when the axle drops/lifts the shaft extends/contracts accordingly. If you have a look at the front driveshaft as opposed to your rear you'll see the difference.

Hope that makes sense. Not very good at explaining things like this without pictures

[Steve]

Yeah Dale what are you on about? graemlins/dunno.gif Hehe! Let us know what you decide on, as I don't have a clue which would be better. :confused: All I can say about you getting a new SYE and Drive Shaft is: graemlins/madfinger.gif

[Dale]

FWIW, I am getting the drivehaft made at the moment at a cost of $350. That includes new greasable unis etc.

A cv shaft wasn't required as the angle wasnt great enough to justify it.

This is for my TJ which is running now, OME lift, 1.5" coil spacers, 1.25"MM and 1.25"BL. Distance between faces of SYE Yoke and diff pinion yoke was 400mm and 100mm differnec in height between the 2.

Already starting to think belly up. Might need that CV shaft after all.

[Phil]

yeah right belly up ,,, then you'll say "don't like the claws" "could do with bigger lift" etc ... must have had a good sales week :D :D :D

[zzzz]

Originally posted by Dale:
FWIW, I am getting the drivehaft made at the moment at a cost of $350. That includes new greasable unis etc.

A cv shaft wasn't required as the angle wasnt great enough to justify it.

This is for my TJ which is running now, OME lift, 1.5" coil spacers, 1.25"MM and 1.25"BL. Distance between faces of SYE Yoke and diff pinion yoke was 400mm and 100mm differnec in height between the 2.

Already starting to think belly up. Might need that CV shaft after all.<font size="2" face="Verdana, Helvetica, sans-serif">is that the double cv (cardan) style drive shaft
or are you doing a wooders on us? if it is double cv then that is nice and cheap and I need the name of the place doing it. hehe. :D

I found a website the other day with the JB conversions heavy duty SYE for US$249, add on some shipping and duty at customs and I am sure you can land that for cheaper than AUS$1100. But importantly you will not really have a warranty from a good local shop to fall back on.

follow this link > tellico online shop (http://www.tellico4x4.com/xfer/slipyoke.htm)

[ 09 August 2002, 09:34 AM: Message edited by: zzzz ]

[Wooders]

Dale,
I got you email - but I'll respond here for others to read.

It is common knowledge that to run a SYE you must get a Cardin joint rear shaft - Well I for one will say that that is complete BS. Both my front & rear driveshafts have simple uni joints at both ends. I have about 5" of suspension lift and I've had no problems for the past 3 years I'm had the Uni-joints.

During the 3 years I have not replaced a single unijoint, heck I haven't even regreased them after mudding etc....Although I think I am about due to replace one shortly.....

IMHO the unis are cheaper (MUCH), easier to replace (MUCH), allow a slightly longer driveshaft (about 2"), are just as smooth a a CV, allow just as much droop as a cv - infact are fairly easy to modify to have a higher operating angle.

The main difference is that you no longer point the pinion upto the output shaft, now you want the angle of the output shaft to basically parrallel to the pinion angle (infact the pinion 1degree below is ideal). This has other benefits in the front - but that's really a sperate question.

As for your lift Dale - well firstly when you do the BU, the driveline angle of the motor/output shaft is going tobe much flater - which will work better IMHO with the unijoint. Also remember with the But I think you WILL need adjustable arms to be able to get the pinion pointed high enough....(but adj-arms will help regardless of the driveshaft option). This brings me to my last thought - I like the pinion pointed low (ie unis)so I know those bearings are getting plenty of lub.

------------------------------------

Now Camel,
With the Stock slip output shaft, the extra driveshaft length required as the axle moves down and away from the transfercase is provide by the driveshaft sliding along the output shaft. There are three problems with this:
1. The output shaft provides the extra length in the horizontal plane only, but the axle is moving in a vertical plane - so in effect as the axle drops it is pulling the shaft down which can lead to bending or breakage of the shaft.
2. To allow the slip movement the stock output shaft is extremely long. making it easier to bend/break. Example open your draw & pull out a pencil, break it in half (easy huh), well now break one half in half again (not so easy huh)....Leverage provided by the extra length is NOT desireable.
3. As said above when the shaft breaks it always seems to break in near the speed gear - just inside the t/case. This is becuase this is the thinest part of the shaft (& near the middle). Now the stock shaft is on 27mm in diameter at that location, however the good SYE kit (AA, JB & Tera) are all 35mm in the same location. This means the pencil is now sharter & thicker. I have NEVER heard of anyone breaking any of these three shafts and they are reputed to be about 50% stronger than stock....

Yes there is a cheap cut&tap SYE on the market, personally I wouldn't look at one unless I was planning to move to an Atlas longer term....

So now with the SYE the slip movement is relocated to the driveshaft, so as the axle moves down the slip movement is in the exact plane required by the driveshaft.
The other benefit fo the SYE, is that not only is it stronger & working in the required direction, but also it has effectively lengthened the rear driveshaft by as much as 4". now that might not sound a lot, but the stock shaft is only 11" in length, so we're talking over 33% longer with dramatically helps manage the driveshaft angles, giveing less strees on the joints and the rest of the vechile for the matter (including the driver).

Although it's something that is hard for many people to appreciate - IMHO the SYE was one of THE best modifications you can make to a TJ...

[Steve]

Correct me if I'm wrong but I think the Auto tranny is shorter than a manual. So my driveshaft would be longer and I'd benefit even more from an SYE? After I regear and go 33's I think an SYE will be the next on the list. That'll make the missus happy! I told her I would be done with the Jeep then! ;) But how many here have said that to the missus before? :rolleyes:

So if I do get an SYE then I might as well go 35's after the 33's I don't even have yet are worn out!

[Dale]

Yeah Zach I'm doing a Wooders. Just a cuppla unis.

I'd be a little hesitant in recommedning the mob I'm using at this stage. Dropped off shaft and dimensions yesterday morning and promised it be ready this arvo. phoned up and now it won't be ready til Monday and I'm really, really, really pissed off about it. Totally fawked up my w/e.

Thanks Wooders.

Belly up is a little way off. Disc brakes and gears/lockers will be first

[oscar_the_grouch]

Wooders...how long did it take u to complete your
PHD in JEEPOLOGY :D :D :D :D

[Wooders]

I'm just a delinquent with too much time on my hands tongue.gif

[Wooders]

AY - The Auto is shorter than the manual - by about 1" I think...

[Wooders]

Reports??? :D

[Steve]

By all reports from Dale the drive shaft and SYE is in and vibration free.

[Dale]

Well, no vibes at all. Actually runs smoother now than it used to.

Works a treat. Very happy.

Glad I did the homework and went the way of the shaft with 2 unis's. Works well and is easy to maintain.