JB Conversions - NP231HD Install
[an error occurred while processing this directive] Short Cuts

By: Greg Colburn - 11/2002

Here is the new Transfer Case ready for it's new home
Support the Transfer Case with a jack stand.
Remove the shift lever, and all hoses and connectors.
Here is a comparison shot of both the old and the new.  With the SYE installed it is a full 5" shorter.

The JB Conversions NP231HD unit is an excellent upgrade for anyone that owns a Wrangler or Cherokee with a transfer case problem. Our Jeep was purchased with 150K miles on it and it had a new driveshaft installed on it.  When the driveshaft was installed prior to the purchase of the vehicle, it was measured incorrectly, and made to long.  The result was a fractured case, and one leaky transfer case.  A new JB Conversions zero-mile NP231HD unit was ordered complete with a larger bearing, wider chain, and a slip-yoke eliminator kit already installed. Once the new transfer case arrived, it was on to the install. It is relatively simple and few tools are actually needed.

First off you want to chock the wheels, and disconnect the battery ground.  Next disconnect the vent hose, electrical plug, speedometer cable, and the shift lever from the transfer case, then remove the rear driveshaft from the rear axle yoke using a 5/16" wrench. Next, support the transmission with jack stands and remove the skid plate. Remove the six (6) 9/16" nuts that attach the transfer case to the transmission. All that is left to do now is slide the unit free from the transmission (It can be pretty snug). Now remove the unit and place it off to the side out of the way.

Once you install the old speedometer gear on to the new case, and fill it with some new oil (it is shipped dry) it is time to install it in to the Jeep.  Lift the unit into position, line up the studs on the case to the holes in the transmission, and slide the unit on to the splines.  Check to make sure that all of the studs are through, and that there is a good fit and begin tightening the nuts on to the studs.  After the unit is tight, plug in the speedometer cable, the electrical plug, vent hose, and attach the shift lever.

That's it!  Now you are ready to measure (You want to measure from yoke face to yoke face- this will give you your running length) for a new CV style driveshaft and kiss your old unit, and any driveline vibration goodbye.


If your transfer case is starting to get cranky, this is the answer that you are looking for.  You can't beat it for the price of a brand new unit especially since it includes the wider chain, and a slip yoke eliminator already installed.  The only information that you will need to provide when ordering is the spline count, and what transmission you are bolting to.  Just get the model number off of your current NP231 and use that when you place your order.


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