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October 8, 2020 at 3:48 pm #403Jason DKeymaster
This thread will be for information about using the Dodge DHD transfer case. These transfer cases all seem to have a dual pattern in the front half casting, and I have a drill jig for redrilling the Chevy pattern. If they were behind a manual transmission, they should also already have a 29 spline input shaft. It may also be that all have the bulky PTO provision as well, but if you run across one that does not correct me here.
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 factory DHD Dodge input shaft, as well as a longer version that may interchange – 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. 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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