As part of my upgrade I am doing away with the slip yoke on the rear of my T-case for obvious reasons. For those who aren't aware the slip yoke causes vibration, a potential for binding at high lifts, and shortened overall driveshaft length. Also with a slip yoke if you happen to twist off the rear driveshaft you will spit out a bunch of t-case oil and likely cook the case trying to get home in front wheel drive. The Advance Adapters Fixed Yoke Kit addresses all of these potential problem areas and allows you to run a double cardan joint at the t-case and a 5" longer driveshaft. When you consider that the stock YJ driveshaft is like 16" or something this is a huge increase.
Here's what the t-case looked like with the slip yoke housing intact

First thing remove the tail housing.

Next the speedo/oil pump housing.

Next remove all of the case half bolts and lift the rear off.

Inspect everything for dirt and wear. Parts and pieces caught up in the oil pump pick-up tube tell you what may have broken and if the pump was starving for oil. In my case, lots of metal shavings and a bunch of silicone pieces, someone used too much silicone, the metal shavings are likely a bit excessive but still normal.

This is what it looks like clean..

Remove the drive chain by sliding the front output shaft out and toward the main shaft.

Here's the mode hub, this is what selects 4 wheel drive when you pull the lever, inspect for wear. Mine looked great, synchro ring looked brand new.

It is three main pieces, inspect them all.

These 2 needle bearings lived inside the mode hub on the original shaft, the new kit does away with them entirely and the hub rides on the shaft. I used a highly sophisticated tool to remove them, a large socket, vice and hammer. Be gentle though, I also wrapped the gears in heavy clothes before holding them in the vice.

Inspect all parts for wear, especially the shift fork, mine needed replacing. Explains all of the shavings attached to the pickup magnet.

Once you have cleaned all of the old silicone, fillings, dirt and anything else that doesn't belong you can reassemble the mode hub and install it onto the new main shaft, here's the old shaft compared to the new shaft.

Affix the snap rings, slide it into the planetary gearset, wrap the chain around it, put the front output shaft inside the drive chain and put it back where it came from.

Install pump and pickup tube and put the rear case half back on and snug 2 bolts up to hold it in place. The shift rail needs to be measured, if it protrudes more than 1" (ideal measurment) then it needs to be cut or you won't be able to shift.

Of course mine was a healthy 1.5 inches so out came the cut-off wheel, try to grind away from the pump opening. Be sure to stuff tons of rags into that gapping hole where the pump goes so those little shavings don't ruin your t-case.. Not bad for a hacker, remember I said 1" was ideal...  

Remount the oil pump pickup and pump to the rear case half and apply a light coating of silicone.

Slid the rear case half onto the front making sure the pickup stays in the pump and the alignment dowels line up.

Once it's all into place, torque it all down.

Install the speedo gear.

Install speedo/pump housing also with a thin layer of silicone.

Install rubber seal onto output shaft and tighten yoke down.

Viola, one seriously upgraded 231 t-case.


Aside from having to take my spare t-case apart to scavenge a shift fork the job was very straight forward and easy. On a scale of 1 to 10 a difficulty of about 4 to 5. Even with taking 2 t-cases apart I still completed this job in about 4 hours.

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