JB Conversions Super Shorty SYE on an NP231

So my wife let me pick out my own birthday present this year and I decided to get JB Conversions Super Shorty SYE. I have been running about 4" of suspension lift with the stock slip yoke for almost a year now and haven't really needed a SYE plus a layoff kind of killed the budget for additional mods. Now that life is back in full swing I am starting to prepare to get the Jeep where I want it to be. The first part of this long slow buildup was an SYE. I want to eventually get a flat transfer case skid and lift the tranny and transfer case up in between the frame rails.

Along with the SYE I also bought the Dakota Digital signal converter from JB Conversions.

The kit includes:
Bearing housing
Output yoke (1310)
Tone ring
Electronic Speedometer sensor
Retaining ring
Yoke nut
Dakota Digital signal converter (optional)

The SYE kit includes a new speedometer sensor to replace the factory one. According to JB Conversions the new speedo sensor is set up for a stock Rubicon. In other words if what you are running is equivalent to 4.10 gears and 31" tires with a 4:1 TC you should be fine without the signal converter. If you are like me and you are not running equivalent to that or you will be re gearing/getting bigger meats you will need the converter to adjust your speedometer calibration.

Dave, Mike and Paul came over to give me a hand installing this and Dave brought his air tools which are always handy to have. We started by jacking up the TC skid and placing a jackstand under the transmission to support the weight of the transfer case and tranny. We then removed the 4 nuts that bolt the transmission mount to the TC skid. We then unbolted the TC skid from the frame and lowered the jack and removed the TC skid.

This gave us the room we needed to disconnect the front and rear driveshaft. After the driveshafts were pulled we drained the transfer case of ATF. Please take note of this picture as it will have some importance later.

After the ATF was done draining from the TC we removed the yoke nut from the front with an impact gun and pipe wrench to hold the yoke and then pulled the yoke off. The yoke was on there pretty good so we used a gear puller to get it off. This worked out very well for us.

We then turned our attention to the rear slip yoke. JB Conversions recommends pulling the entire TC but we decided to leave it in place. We removed the rubber boot and retaining ring. To get the dust shield off we used a chisel and beat the crap out of the dust shield until it was deformed enough to pull away from the bearing housing. We then removed the mainshaft retaining ring. In other write ups I have seen this was a troublesome process. I already had a lock ring pliers in anticipation of this and doing it the way most people did was indeed troublesome so I found a better way. What I did was got the end of the pliers into the hole on the retaining ring and pulled it away from the groove it sat in. Once I did that it literally peeled right out. We then removed the bolts holding the bearing housing to the TC and slid the bearing housing off. After that we unbolted the rear half of the TC from the front half and removed the rear half to expose the mainshaft assembly.

We pulled the mainshaft and front output shaft and chain out and set it on the bench where we swapped the hub and sprocket assembly from the old main shaft to the new JB Conversions main shaft. When you pull the retaining ring from the old main shaft you can go ahead and throw it away as JB Conversions provides you with a new one in their kit. Here is a picture of the old main shaft next to the new one for comparison of the length.

After swapping the hub and sprocket assembly and installing the new hub retaining ring we installed the new mainshaft back into the TC. We then put the chain on and re installed the front output shaft as well.

Then the back half of the TC was re attached after running a nice thick bead of RTV on it. Be careful here to make sure that the pickup and oil pump are aligned properly when putting the back half back on. We then placed the tone ring on the mainshaft and installed the new bearing housing. We also ran a nice thick bead of RTV on the bearing housing before installing. Once the bearing housing was back on we put the new yoke on and ran a bead of RTV on the new yoke nut before torquing it down.

We removed the old speedometer sensor and replaced it with the JB Conversions sensor and re installed the TC skid without the 1" TC drop that I had previously installed with the lift so it was back to stock location. We then refilled with TC with Castrol ATF +3.

We next wired up the Dakota Digital (DD) signal converter. It is my intention to place it behind the glove box so we ran 3 18 gauge wires from behind the glove box under the carpet and down through the drain plug behind the driver's seat coming out just a little bit behind the TC. From there the wire follows the factory speedo wiring to the TC. The 3 wires we ran are for signal in (from speedo sensor brown wire (which we cut in half) to DD Sig. In.), Out2 (from DD Out2 to the brown wire leading in to the stock speedo connector), and ground (from DD Gnd. to tap on speedo sensor black wire). We heat shrinked our connections where we cut the brown wire and used electrical tape on the tap and over the heat shrink to water proof it somewhat. For power I wrapped a wire around the cigarette lighter fuse and shoved it into the fuseblock and connected it to the pwr terminal on the DD. This was just temporary to test it but I do want it on a switched power source.

The included instructions say to turn on dip switches 1,2 and 4. This will give you a wildly inaccurate reading (60 mph in 2nd gear pushing 1500 RPM for me). For now I have just dip switch 1 on and that seems to be off about 10%. Good enough for now until I get my new rear driveshaft made. Then I will re calibrate and update this post.

Now for the mistakes.

We didn't use the drain plug to drain the TC, but used the detente bolt. What we didn't notice was the detente poppet and spring came flying out when we drained the TC. I discovered it after we had already taken it for a drive when I was draining the old fluid out of the catch pan. In case you are wondering what these parts look like:

Luckily I had the good ol' FSM to show me where it went.

And after reasoning it out with Lew last night in chat, I dropped the TC skid, drained the TC again and re installed the detente poppet and spring. Thanks again for the help Lew!

The other mistake I made was not reading the Dakota Digital instructions fully. When we made our first test ride we had no speedometer readings at all. After re reading the instructions it turned out that I had the wrong dip switches set and the problem was solved.

Tomorrow I will order the new rear driveshaft (18" ) and once it is installed I will complete the write up on this install.

Overall the SYE install was pretty easy. It was straight forward and the instructions were pretty clear. And to give credit where credit is due it is very helpful to have a great group of friends that will give you a hand with the install.


Today I picked up my new double cardan driveshaft from Oliver's Driveshaft in Winston. I had him make me an 18" shaft with a 1330 U joint for the yoke on my Ford 8.8 and 1310 U joints for the mainshaft yoke. Fred is a great guy to do business with and I feel he does pretty good work at a very reasonable cost. Reasonable in this case being $215 for everything. Here is a pic of the new driveshaft next to the old rear driveshaft:

I couldn't wait to install it once I got home so I didn't.

Luckily for me everything worked out great. I had no vibrations at any speed, at least none up to 80mph. Not that I had any at speed with the factory setup. I used to have a bad vibration at take off under hard acceleration though. That is now completely gone with the new setup. I must say I am very pleased with how this whole project turned out.

Overall the SYE install was pretty easy. It was straight forward and the instructions were pretty clear. And to give credit where credit is due it is very helpful to have a great group of friends that will give you a hand with the install. A tip of the hat also goes to Fred at Oliver's Driveshaft for getting the driveshaft made quickly and at a very reasonable price.