jpthing's XJ rear driveshaft setup

[jpthing]

Howdy Y'all.

I was having issues with the rear driveshaft on my XJ and I devised an interesting alternative setup which has worked well for me.  It's been on my Jeep for about 6 months now and Ive been really happy with it, so I figured I would share for those who may be intereseted.

 Disclaimer: It may not work for you. You may think it's stupid. If that's how you feel, I would strongly suggest not doing this to your Jeep. Go spend big bucks doing it the "proper" way. If the idea of hockey puck body lift or bumpstops or bastard leaf packs makes you upset, I would suggest moving along to reduce your stress levels. This is a thread about a cheaper alternative to the norm. I should also point out that this thread is not for those who think they know everything, since a mere mortal's driveshaft would obviously be of little concern to one of these demigods.  I have taken my time to explain myself  fully, so that even those who don't know everything will find the information "accessible". Again, this may be irritating to those who do know everything. Sorry. I guess...

[jpthing]

So first I will tell you abnout the problems that I was having before this setup.

I am not the hugest fan of the driveshafts used with a SYE. Now stop getting all upset and let me explain. obviously if you are going to lift a TJ more than a little, there is no alternative to the SYE, double cardan joint driveshaft with the splined telescoping section. After all the driveshaft is only 1 foot long. So despite my dislikes (more about this in a second) about this type of rear driveshaft, it is the only option for the rear of a lifted TJ.\

Whats my issue with the SYE/double cardan joint rear driveshaft? Simple: Cost, complexity and ease of repair. A SYE kit is around $300, and the custom rear driveshaft is around$500-$750 more. Now this is a good setup, I'm not dissing it, but within a year or two I started to have problems. With the amount of Maclean mud I've been through, I had problems with the blue coating coming off of the splined section. When this happens, there is no option except for having a driveline shop weld on a new splined section. At this point the female side (yoke) should be replaced too, due to damage caused to the splines by running with the blue coating damaged. I also had problems with the double cardan joint itself. frequent mudbaths and less frequent greasing resulted in a need for maintenance. Although I got pretty fast at changing out the two ujoints and the ball kit which resides within, I still always found it to be a hassle. And before too long there was noticeable wear to the machined surface on the little cylindrical part that contains the little spring and installs into the cv ball. (I'm not sure what this part is called, but it's inside the double cardan joint and  the joint will quickly fail if there is damage here). The problem is that the little machined surface, as with the blue coating, cannot be repaired in the garage. If you wear that part, it must be cut off of the driveshaft and have a new part welded on and the shaft rebalanced...$300+ from my experience.
So basically the reasons why I wanted to move away from the double cardan joint on the rear of the Xj was that it is more of a hassle to maintain (3 u-joints, two splined parts, ball kit, and machined stub on a double cardan vs. only two u-joints on a conventional driveshaft) Additionally, the Double cardan shaft has two parts (blue stuff on splines and machined bit) which cannot be replaced by the jeeper, which to me is lame. I like to fix my own Jeep, and I hate giving Pat's driveline money unless there is no alternative.

Of course there  are reasons why the double cardan joint is so widely used by wheelers. The main ones I am aware of are that the DC (double cardan) can handle much greater angles, due to it's "splitting the angle" between the two upper u-joints. When considering angle on u-joints there are really two seperate factors, running angle, and maximum angle (almost certainly not the correct terms) By running angle I am referring to what angle a u-jopint will happily purr along the highway at without excessive wear or vibration. By maximum angle I am referring to how far the u-joint can flex before the yoke ears collide. The running angle must be within the allowance of the components or you will get vibrations. This is how it is usually explained, but it would be more accurate to say that too great of a running angle would cause "greater vibrations than normal" or "excessive vibration" since there is always some level of vibration in a driveshaft.  So my goal was to find a traditional, 2 u-joint rear driveshaft which would have acceptable levels of vibration, and wher the ears of the yokes would not collide at full droop.

[jpthing]

The TJ's stock rear driveshaft is a beatiful thing and rarely gets the rspect it deserves. Obviously it doesn't work with a lift, but consider the flex and articulation that a stock TJ has in the rear, then remind yourself that the driveshaft on an auto trans TJ is less than 12" long and you'll realize it's different than most. To deal with the TJ's increased rear articulation the jeep engineers devised a setup for the TJ rear driveshaft which was very different than what had come before.
The first big difference is the output housing and output shaft on the t-case. Contrary to popular belief, the rear driveshaft on a stock TJ can be removed and you will not lose your tcase fluid. (unlike the XJ and YJ which do not use this design). The TJ's output shaft has it's own seal in the T_case and rather than the output yoke sticking into the tcase and the splines being bathed in atf, The tj's output shaft is completely external and the splines must be greased. The Tj stock setup uses a rubber boot here, to keep dirt off of the splines, the others haver the splined part inside the tcase instead.
The next thing is the output shaft length. I have heard or read several people mocking the TJ engineers for the fact that in such a short vehicle the tcase output shaft was actuall longer than on yj's, leading people to assume that a longer output shaft would equal a shorter driveshaft. Beleive it or not, the longer output shaft actually results in a longer driveshaft as well, and one that is less prone to vibe out. This is because the TJ rear driveshaft components are different than most: The slip yoke is designed to allow the tcase output shaft to go all the way into the yoke, to within a half inch of the upper u-joint. This is how the driveshaft length is increased. Despite the fact that the TJ output shaft is about one inch longer than those that proceded it, it actually allows one inch more driveshaft. And the slip yoke is less prone to vibration because more of it's mass is wrapped around the output shaft rather than hanging off the end of it, flailing about.
Additionally the TJ yokes are beatifully designed for huge maximum angles before the yokes collide, compared to other yokes I have seen on other Jeeps.

So you're probably figuring out where I'm headed...using stock TJ parts on a lifted chrokee.

[jpthing]

To do this set up you will need a stock TJ tcase output shaft and output housing, a stock TJ rear driveshaft (these three can usually be had for free) and the rubber boot, slinger, and two metal bands that seal up the slip yoke (i went to the dealer for these). The slinger and the bands are always damaged in removal, and better new when it comes to a rubber boot, I figured.

You will need to open up your tcase, and swap in the TJ output shaft and housing. new seals would be a good idea. Doing this is about the same complexity as doing an SYE.

Then you will need to take the Jeep to a driveline shop, and have them install a longer tube onto the TJ driveshaft components and balance. Keep in mind that thicker walls are stronger against damage but more prone to vibrations than the standard wall thickness. For this reason I had them go 1 step thicker but did not select the tuffest tube they had, as I knew I would probably have issues with vibrations with 4" of lift and a standard driveshaft.

When I did this it worked great. There was some vibration at some speeds, but way less than before with the messed up DC shaft, and way less  than what some of my friends considered tolerable on their jeeps. I experimented with rotating the yokes 180 degrees, and dropped the tcase 1/4 inch and the vibes were barely noticeable.

[jpthing]

Getting my driveshaft lenghthened at Pats cost around $350. I'm pretty sure they're the most expensive shop in the city, though, and that it could be done elsewhere for a little over $200.

The end result is a simple driveshaft with only two u-joints to replace or grease that has minimal vibes and can handle decent droop. Another benefit is that the vehicle can now be driven with the rear driveshaft removed without the tcase losing fluid.

I am climbing into my flame proof suit and bracing myself.

[JackstandJohnny]

ok i'm gonna start the flame

why do all that work to NOT ELIMIATE VIBES?  a 'little' vibe is TOO MUCH. 

second;  its ALOT EASIER to grease your ujoints/driveshaft after every time you wheel.  thats maintenance.   thats a lot cheaper than what you described.


man who do i talk to about getting the last 20 mins of my life back?

[jpthing]

ok i'm gonna start the flame

why do all that work to NOT ELIMIATE VIBES?  a 'little' vibe is TOO MUCH.  

second;  its ALOT EASIER to grease your ujoints/driveshaft after every time you wheel.  thats maintenance.   thats a lot cheaper than what you described.


man who do i talk to about getting the last 20 mins of my life back?

I now have a simpler setup which works better and is easier to maintain. To me that's good.

My suggestion for you: If you don't like this idea don't use it.

Go ask the guys at a driveline shop...there is no such thing as no vibe.

Oh, and talk to yourself about your lost 20 minutes...you read it!

[dac]

man who do i talk to about getting the last 20 mins of my life back?

I believe there are several ways to do this, one of which is making "sticky".  I tried to explain this to my wife but I don't think she understands.  Either that or figures I'll kick the bucket that much sooner.  

I like my sye and DSI drive shaft.  No vibes from the drive shaft and it's easy to grease (I have a nice blue line on the underside of my jeep because I get bored and grease stuff).  The trouble with the short drive shafts, or mine initially, was that even if they are in spec they can still vibrate.  Standens was able to fix it for me so I could remove the t-case drop one of the shop in town installed because "sometimes you need the t-case drop with a sye".

[jpthing]

yeah I'm not arguing that the SYE and Double cardan driveshaft is bad.
It costs close to $1000 to set up, it should be good!
My setup cost around $350. And needs less maintenance.
I'm not saying SYE's suck, I'm just stating what my setup is and why.
SYE's are great...but they are not the only option on an XJ.
Again, I prefer stuff I can fix myself, like this setup.

I would way prefer having two u-joints that wear out every 6 months to having to drop $700 for a new driveshaft every few years. The u-joints are quick and easy to do yourself.

(the u-joints do not, so far wear out every 6 moths, this was just an example of worst case )

[jpthing]

Which

I believe there are several ways to do this, one of which is making "sticky".  I tried to explain this to my wife but I don't think she understands.  Either that or figures I'll kick the bucket that much sooner.   

I like my sye and DSI drive shaft.  No vibes from the drive shaft and it's easy to grease (I have a nice blue line on the underside of my jeep because I get bored and grease stuff).  The trouble with the short drive shafts, or mine initially, was that even if they are in spec they can still vibrate.  Standens was able to fix it for me so I could remove the t-case drop one of the shop in town installed because "sometimes you need the t-case drop with a sye".

which shop told you a tcase drop with an SYE was normal? That's pretty lame. And how did Standen's fix it?

[dac]

I'd rather not say which shop it was.  I still go there as they've always treated me well; although I knew the comment was bunk.

Standens had the vehicle up on a hoist and straightened it while it was mounted.  Something to that effect.  It didn't vibrate on the machine when they tested it (no working angle) , but it did when it was installed (working angle).

[jpthing]

Are we talking about a 4x4 shop though?

Straightened what?

[dac]

sorry, Standens straightened the driveshaft.  It was off where the bottom part of the double cardan welds to the shaft.

[cLAY]

Well I give credit where credit is due, 2 thumbs up!

I might try this on my ZJ. On both my old XJ and ZJ I'm still running a stock driveshaft and no vibes. That's with an 8" lift. How did it do it?  The rear axle is a D60 with it pushed back about 1". The pinion snout is MUCH longer than on a D35 which negates the need for a longer driveshaft. Also by manipultaing the pinion angle I have been able to eliminate any vibes. For extra angle I'm running a YJ yoke. Works fine for me the only thing I worry about is if I do take out the rear shaft I'll lose my t-case fluid. As you described a TJ output will solve this.

If you still have vibes I would play with the pinion angle, a few degrees below pointing straight at the  t-case output is a good place to start. I don't see why you shouldn't be able to eliminate vibes on any lifted XJ with a t-case drop and proper pinion angle.

I should clarify that the long arm kit on my ZJ drops the t-case about 1" and I had about a  3/4" drop on my XJ.

I'll have to think about this, my other idea was to do a homemade SYE using a yoke that would allow me to run a stock front driveshaft in the rear. More complicated, about the same money but I only need one spare shaft to cover all or could even swap the front to the back in a bind.

[Bnine]

SYE's do not require CV shafts. For apps like an xj you can still run a fixed output (SYE) and 2 joint shaft.

Two joint shafts have more total angle ability then CV's. CV's can operate at higher angles without vibration but but bind sooner then a 2 joint.

Best of both worlds is a fixed output and 2 joint shaft. Like d300's and CJ's.

Just some clarification there ona few points