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October 8, 2020 at 3:44 pm #401Jason DKeymaster
This thread will be for information about using the light duty Dodge 241 transfer case behind the Allison. This transfer case requires a clocking ring to bolt up to the Allison and typically an input shaft change as well. I highly recommend Torque King 4×4 for your input shaft purchase, if you want to try and save money there are many cheap import shafts on the internet but be aware that they may be poor quality. Depending the exact shaft your case needs, you may be able to swap in a longer input shaft to make up for the thickness of the clocking ring. Your assembly number on the round tag that is attached to the back half of the t-case will aid you in finding the best input shaft for your case. The picture below shows a clocking ring on a 273 Dodge transfer case, with the tone ring installed for the output shaft speed sensor install in the Allison extension housing. Most clocking rings are able to be used on any of these t-cases because they share the same bolt pattern. It is possible to install the ring facing either direction, but if you choose a particular face you may have to slot one of the holes in the Allison extension housing for all to match up.
Installing the OSS sensor in the extension housing of the Allison enables the use of low range operation with no issues, otherwise, when the sensor is located in the extension housing of the transfer case, another option is needed to avoid limp neutral problems when operating the vehicle in low range. I believe it does take a little machine work to put the tone ring on the longer Dodge input shafts, but they fit right on the shorter Chevy 261 XHD input shafts that have been used in the past. None of my customers have had any cracking problems from drilling the hole in the 6 speed extension housings – but I would not recommend using a 5 speed housing, they are already known to crack.
Clearance measurements with a special tool are highly recommended when removing and replacing the extension housing on the Allison, so it’s best to just drill the hole with it on the transmission, it’s not a super critical kind of thing. The sensor that is typically used is for the 261 XHD behind the Allison. It requires a M22x1.5 tap and a 20.5mm drill bit. As an alternative I have also ran a 7/8” coarse tap over the sensor for 7/8” coarse threads in the extension housing.
It may be required to cut or grind the land off the sensor to reach the tone ring with close enough air gap. The way the sensor clearance is set is by stacking some masking tape on the end of the sensor and threading it in,
counting the thread rotations and then marking the indexing. .020 to .030” clearance is what I recommend targeting. Stack up some tape enough to get that thickness and then put it on the end of the sensor. Run it in, mark it and then take it out and pull the tape off. Then seal the threads up with Ultra Black Silicone or equivalent.
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