• NAXJA is having its 18th annual March Membership Drive!!!
    Everyone who joins or renews during March will be entered into a drawing!
    More Information - Join/Renew
  • Welcome to the new NAXJA Forum! If your password does not work, please use "Forgot your password?" link on the log-in page. Please feel free to reach out to [email protected] if we can provide any assistance.

Homebrew 3103-27CV SYE Details

xjbrian

NAXJA Forum User
Location
California
I have a 1999 XJ with a 4.0L engine, automatic, NP231 transfer case, Chrysler 8.25 rear axle, and a new 3 inch budget boost. I had vibes so I tried a transfer case drop. It didn’t work, so I decided I needed a SYE. I started looking at how to do it cheap. I found lots of discussion about home brew SYEs using the 3103-27CV yoke and front drive shafts out of XJs, but I couldn’t find guidance where to cut the yoke and transfer case output shaft. I hope this post helps others.

I bought my yoke from drive-lines.com. They were much cheaper than anyone else I found, $88.42 delivered. When I got the yoke, I knocked the cap out of the end of it, and noticed the splines did not go all the way to the end. I also noticed that the splines on the transfer case output shaft do not go all the way to the transfer case seal. It worried me that the shorter I cut the transfer case output shaft the less spline engagement I would have. I asked some of my mechanical engineering friends at work how long the splines need to be. They looked it up in their old text books and told me that the spline face only needs to be as long as the pitch diameter, which in our case is roughly the diameter in the middle of the face of the spline. This means you need about 1.1” of spline engagement.

I pulled a front driveshaft out of a 1990 XJ 4.0L automatic with NP231 transfer case at the junk yard. It was $29.57 with the entrance fee, 3 different taxes and the core charge.

I also bought a grade 8 ½” washer that just fits the flat spot in the yoke if you pound it in with a drift. I also used a 3/8” fender washer on top of that then a 3/8” grade 8 washer then a 3/8” grade 8 split washer and a 1” long 3/8” 16 bolt. With a few dollars for a bolt and washers it cost a total of $121 for my SYE.

I started looking online for measurements of the yoke, driveshaft, and output shaft. It wasn’t going real well, so I measured everything myself. The attached pictures show all my measurements.
Slide1.JPG

When I put it all together I wanted the back of the yoke to rest on the shoulder of the transfer case output shaft to add some stability and so I would not have to weld the washer to the yoke to keep the yoke from sliding forward on the transfer case out put shaft. Most of the write ups I have seen have not talked about that issue for the newer sealed transfer cases. When I slid the yoke onto the shaft I ground the shaft down just a little, about 1/64” shorter than the yoke, so that when I bolted it down there was pressure keeping the yoke pressed up against the shoulder on the shaft.
Slide2.JPG

The next measurement is critical. The driveshaft must not over compress or extend. I measured the drive shaft and fully extended it is about 34”, fully compressed the catalogs say it is 30.66” and my measurement confirmed it. I sagged my rear suspension and the drive shaft only needed to extend 0.5” so I wasn’t worried about how long it would get. As a matter of fact I can lift it another 3” and still not worry.

In compression the numbers get a little tighter. With 1.75” cut off the output shaft there was 32.75” from the pinion yoke to the output shaft. The drive shaft is 30.66”, add 1.25” for the distance from the end of the yoke to the flat spot on the yoke where the washer will rest on the end of the output shaft. That gives you 31.91” total length. That only leaves 0.84” to compress. Using a little trigonometry it shows that I will only compress about 0.35” with the suspension fully compressed to the bumpstops. That leaves me with 0.49” of clearance in compression and lots of room to extend.
Slide3.JPG

To cut the output shaft I removed the old driveshaft started the engine put the car in reverse and used an angle grinder to cut. It worked great. I cut it a little long and the used the grinder to trim it. To cut the yoke I did it the same way. I slipped the yoke on the output shaft backwards and used the angle grinder to cut the end of the yoke off. I had to put a hose clamp on the output shaft when cutting the yoke to hold the yoke out a little so when I cut through the yoke I didn’t hit the output shaft.
 
Nice! :thumbup: This is exactly what I've been considering for a while, but was always too lazy to actually do the math and drawings. Glad to know it'll work out well.
 
Yeah, go-jeep's page is another good one - doesn't give quite this level of detail on some things I was thinking about though (like I said before.) Glad to know I'm also not the only one using a half-inch grade 8 washer instead of drilling a hole in the existing endcap on the slip yoke, though instead of doubling up washers and using a 3/8 bolt I got a 1/2-13NC tap and am going to use a 1/2 grade 8 bolt to keep the yoke on.
 
That is awesome bro, I have the same yoke fromt he same folks at my house, and I was gong to have the yoke "bored" to slide all the way into the output shaft seal. Have you considered doing this instead of just ending it at the shoulder? Very nice writeup, and great diagrams, that took you some time, and for that I really appreciate it, and I will be using your specs and write up to complete mine. Definately the msot thourough I have seen for the 231 case.
 
Thanks for the write-up
I just received my Yoke today from High Angle Driveline $86.69 delivered.
So I will be attacking it tomorrow night.
Wish me luck, I can't cut a straight line or drill a straight hole
to save my life :eek:
 
Good luck,

You can cut it straight by keeping it spinning. Drilling it was a little tougher for me but it still turned out pretty good.
 
Nice write-up! Can you post some pics of it installed? I have the same year and plan on doing this. I did a homebrew BB and have 2inch lift in rear and vibes. Most people don't notice them but they are driving me nuts. I want it fixed and this seems a good way to go.

Thanks.
 
That is awesome bro, I have the same yoke fromt he same folks at my house, and I was gong to have the yoke "bored" to slide all the way into the output shaft seal. Have you considered doing this instead of just ending it at the shoulder? Very nice writeup, and great diagrams, that took you some time, and for that I really appreciate it, and I will be using your specs and write up to complete mine. Definately the msot thourough I have seen for the 231 case.

I have this exact same setup as well and did exactly what xjnuttier is talking about. Made it feel that much laterally sturdier to me. Like everyone else said, great write up and detail. Cant beat a SYE for under $150.
 
Thanks for the write-up
I just received my Yoke today from High Angle Driveline $86.69 delivered.
So I will be attacking it tomorrow night.
Wish me luck, I can't cut a straight line or drill a straight hole
to save my life :eek:
X2 on what xjbrian said, cut it with it spinning - turns your jeep into a lathe for you. I'd also center punch the end of the shaft while it is spinning with a 1/8 drill bit to make centering the bolt hole easier. Check go-jeep's page on SYEs, it covers all this and more. Don't try to tap the hole with it spinning though, that's a great way to learn how to extract a broken tap from a partially tapped hole!
 
On 96 and later XJs the transfer case is already sealed. Go to go-jeeps page he did a great write up on how he did his with a pre 96 XJ.

The reason I did my write up was to show you can do the 3103-27CV yoke hack n tap and use a factory front driveshaft together. There are lots of write ups on using them individually but I couldn't find anything with details on using them together.

Go-jeep is the man. I have referenced his write ups many times as I have worked on my lift.
http://go.jeep-xj.info/HowtoSYEconversion.htm
 
Got mine done today :D
Mine is a 97 NP242, I also just installed an 8.25
Thanks for this great write-up.
This and GoJeeps write-up were a big help.
I like the way you gave nice illustrations and precise measurements.
GoJeep gave nice real photos.
I chose to use mostly your writeup because using Go-Jeeps measurements
of cutting the Shaft to 1.25" of splines only leaves .75 of spline engagement with the 3103-27CV yoke and I that just does not give me the warm and fuzzy feeling.
However If I were to do it again I would Tap it to
Go-Jeeps specs of 3/8-24 (UNF),
I used 3/8-16X1" Grade 8 Bolt, Grade 8 1/2" Washer and 3/8" Fender washer and Blue Lock-tight
I must have got a chessy Tap, because Tapping was extremely hard and slow going, Drilling was like cutting through hot butter.
I only have about 1/2" of compression available on the Driveshaft, so I think I may have it shortened another 1/2"
I also installed *4 Shims in the rear-end, this sits me at *2.5 Driveshaft angle, not perfect but should be close enough

IMG_0064.jpg


IMG_0071.jpg


IMG_0069.jpg
 
Last edited:
Got mine done today :D
Mine is a 97 NP242, I also just installed an 8.25
Thanks for this great write-up.
This and GoJeeps write-up were a big help.
I like the way you gave nice illustrations and precise measurements.
GoJeep gave nice real photos.
I chose to use mostly your writeup because using Go-Jeeps measurements
of cutting the Shaft to 1.25" of splines only leaves .75 of spline engagement with the 3103-27CV yoke and I that just does not give me the warm and fuzzy feeling.
However If I were to do it again I would Tap it to
Go-Jeeps specs of 3/8-24 (UNF),
I used 3/8-16X1" Grade 8 Bolt, Grade 8 1/2" Washer and 3/8" Fender washer and Blue Lock-tight
I must have got a chessy Tap, because Tapping was extremely hard and slow going, Drilling was like cutting through hot butter.
I only have about 1/2" of compression available on the Driveshaft, so I think I may have it shortened another 1/2"
I also installed *4 Shims in the rear-end, this sits me at *2.5 Driveshaft angle, not perfect but should be close enough

IMG_0064.jpg


IMG_0071.jpg


IMG_0069.jpg

Now you need to go back and do it again.Remove the dust shield and cut the shaft back till the yoke rests on the shoulder.You dont have enough comp left in the slip yoke and it will bottom out!
 
Now you need to go back and do it again.Remove the dust shield and cut the shaft back till the yoke rests on the shoulder.You dont have enough comp left in the slip yoke and it will bottom out!

This is a post 96 NP242, the Yoke is resting on the shoulder.
 
Back
Top