Jeep XJ

My Jeep

Rubicon Express Hack-n-Tap Slip-Yoke Eliminator
and Driveshaft

Update: September 5, 2005

I have had the RE rear driveshaft off my Jeep for a month now. Amazingly, almost all of the vibrations that I have been enduring since the regear to 4.56 disappeared immediately so it looks like the RE shaft has caused me yet another headache... I'm driving around in Front-Wheel Drive until I can install a new SYE and rear driveshaft; the worst part of this is that because of budget and time problems, I have never taken the RE shaft four-wheeling so it hasn't been bent. It's just out-of-balance from the manufacturer. Coupled with the other driveshaft issues I've had from the RE kit, I really can't recommend the Hack-n-Tap and RE driveshaft in the future.

After installing the 4.5" Rubicon Express lift, I had some pretty serious vibrations. Using the 1" transfer-case drop helped, but just cruising around town made my teeth want to shake loose some days. I ordered the RE1807 Slip-Yoke Eliminator (aka Hack-n-Tap) and new driveshaft, along with an RE1670 trackbar brace.

This is what I got initially from RE.  I don't know about you, but there could be some issues those two pieces together.
These were the initial parts I received
To the left are the original parts I received. I didn't even notice a minor fitment issue for a few days, as I had both parts sitting on opposite sides of my desk. It wasn't until I was talking to RE about a different issue that I realized there was no way those two parts were ever going to bolt together without some serious help. Somehow the wrong part had made its way into my order; it's rare but understandable. Justin at RE did an excellent job of taking care of the mixup, and they offered to send the correct driveshaft out immediately, although I wouldn't be able to install it for another week or more.

This is what I got Monday. These should bolt up much more easily once I figure out where and when I can do the Hack-n-Tap. You can see the SYE on the left, with the flange of the shaft next to it. This looks so much better...
These look better...

On initial inspection of the replacement, the parts looked excellent except for some cosmetic issues with the driveshaft. The driveshaft box was pretty well beat up but I didn't think much of it - I expect it will see some beating in the next couple years anyway. While checking out the small parts bag I was glad to see a change had been implemented sometime since my friend Tiffster did her XJ Hack-n-Tap a few years ago; in her review she had groused about having to find a 21/64" drill bit but I noticed there was now one included in the packaging along with the proper tap. Cool, that means I don't need to invest in a good drill bit set yet; I lost my last ones during a prior move.

If you don't have one yet, you still need to supply a tap handle. I don't recommend using a wrench unless you also have an easy-out to remove the broken tap. FYI, I did the installation with the transfer case installed in the Jeep, but there are a few pictures for reference here that show the t-case on my workbench.

Block the wheels and use the e-brake because the Jeep will want to roll when you disconnect the driveshaft. I once watched a kid almost get run over by his CJ-5 when he neglected that piece of safety advice...
Use a strip of 1" masking tape to mark the amount of splined surface to keep. I marked mine out to about 1 1/8" to allow an additional splined length and started cutting with a circular saw and metal cutting blade. You can use a grinder if needed instead though, whatever you need to make a mostly-straight cut. I have heard a few recommendations to keep the t-case in 'N' so the output shaft will spin, on the theory that it also helps keep the cut straighter.
Leave an inch of splined surface on the output shaft
An example of how much was removed

Use a file or a grinder to chamfer the edges of the cut, and tap the flange on. Use a rubber mallet or dead-blow hammer to tap the flange onto the shaft. Don't get overzealous whaling away on the flange though since you are beating on t-case bearings. Contrary to popular belief and the instructions, that flange isn't coming off again anytime soon. Use a centerpunch to mark center and then drill a pilot hole. After making the pilot hole, use the supplied 21/64" bit to drill a hole 1.25" deep.

Clean out the hole using some spray lube or brake cleaner and tap it, again using the supplied tap. Use a tap handle, not a wrench to turn the tap and make sure it goes in as close to the plane of the hole as you can; otherwise it could very easily mis-cut the threads or break. When complete, remove as many of the cuttings as you can and then bolt the flange in place using the supplied 1" long bolt. I used red Loc-Tite on the center bolt.
Bolt the new driveshaft up with at least one bolt to hold it in place, then use the supplied straps (or yokes, if so equipped) to hold the rear. Once the driveshaft is 'up' put the t-case in Neutral and begin tightening the bolts. Only do this with an assistant/safety observer, but I rolled the Jeep back and forth to present each of the four mounting bolts on the flange. Again, red Loc-Tite was used on the four nuts as a supplement to the Nylock nuts because I don't feel like letting this loosen up on the highway. Make sure everything's tight and drive off...I'd recommend rechecking everything after 100 miles or so but that's it. It's a pretty straightforward swap; the bolts and Nylock nuts use 5/8" wrenches and because of the proximity of the tailshaft housing it's probably easier to use two wrenches and skip the ratchet and socket.

The completed assembly

SYE and driveshaft installed
The finished installation

Update Oct 31, 2004
I've had some vibration problems on the Jeep and couldn't figure them out until I looked closely at the RE driveshaft. As you can see in the following photos, the endcap with the Zerk fitting has popped off.

After I dropped the shaft while upgrading my e-brake, I realized why the collar popped off. Unlike every other greasable assembly I know of, this driveshaft had no relief point for the grease pumped into it. Now, this should have been at the lower (axle) end of the driveshaft so the grease could lubricate the splines. I greased the driveshaft and the rest of my Jeep at every oil change, so in the last year since installation every pump of grease has only filled the driveshaft until it finally popped!

While I have recommended Rubicon Express lifts and parts including the SYE and driveshaft in the past, I can't believe the problems I've had from this simple driveshaft. I talked to Mike @ Rubicon Express and their 'solution' would be to have me send the driveshaft back for "evaluation" by their builder, Driveline Service Corp in Sacramento. This would be at my cost, and there's no telling how long it would take to get it back to me; in the meantime I would be front-wheel drive only... I decided to keep the shaft myself and drilled a small relief hole in the bottom. There was actually a plug weld in the bottom plate where a relief hole should have been, but it was completely sealed. To minimize shavings in the body of the driveshaft, I compressed the assembly while drilling. I knew I was through the endcap when it spurted grease all over the drill bit. After that, I could press the zerk fitting back on again - needless to say I'll keep an eye on this in the future.

Update Sep 5, 2005
As was noted at the top of this writeup, I finally tracked down most of the rest of my vibrations. I'm really anal about the maintenance on my Jeep, and also track "oddities" that bother me with it. While making plans to swap out my transmission, I realized that the harsh vibes on the XJ really sarted in earnest when I regeared the rear axle to 4.56 from the stock 3.55. This causes faster driveshaft rotation at the speeds I normally drive, so an out-of-balance shaft would be more prone to vibes. Sure enough, once I pulled the rear shaft out and drove around in front-wheel drive the shakes were almost completely gone. The sad part about that is that I haven't had a chance to do any four-wheeling in the XJ since installing that RE driveshaft awhile back so I know it's not bent...

Look for a writeup in the near future on a PORC HD231 SYE.

e-mail Jim
created: September 9, 2003
Updated September 18, 2005