Words by Bryan Irons @bryanirons
You have to be a special kind of nerdy to get giggly over part number deciphering and acronyms. I’m not talking about the “Wut R U Doing?” texts I get from my daughter, that’s a whole other language. No, I’m talking about the day-to-day codes and shortened wording in order to keep everything accurate and avoid confusion. The last cypher I had to break down was “NP241DLD SYE”.
If you’re following along and that jumble of letters and numbers made sense to you, great. However, if it looked like Elon Musk’s kids name, fear not. This will all get cleared up as we continue to cover New Process chain-driven transfer cases. On top of that, a recent installation of a Slip Yoke Eliminator (SYE) from Tom Wood’s Custom Driveshafts let us know what to look out for in one of these aluminum boxes.
“ NP” stands for New Process. The company New Process Gear made transfer cases and transmissions found in many major manufacturer’s vehicles since the beginning of the automobile or at least as far back as 1913. Since about 1990, the chain-driven variant discussed here are found primarily in Mopar, Ford and GM vehicles. The “NP” and the rest of the numbers can be found on a round metal tag screwed into the back of the transfer case and is easy to spot as they are typically red.
The three numbers that follow the manufacturer stamp depict three major components of the transfer case. In our case, the 2 of 241 tell us that we have a 2-speed transfer case. The numeral 4 is the strength level. This number ranges from 0 to 9 and has no real basis on factual numbers other than 0 is made of playdoh and 9 is “strong like tractor.”
The final number, 1 in our case, depicts how the transfer case is shifted and what options it may have. For us, the 1 is what we wanted; a part-time, manually-shifted unit that fits perfectly in the 1999 project Dodge Dakota that’s getting ready for a complete drivetrain swap.
Some of the New Process variants have a final letter or two. These stipulate what manufacturer the transfer case was made for and possibly a sub-variant. To truck nerds, “D” is for “DODGE” and “LD” stands for the “Light Duty” version.
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As mentioned earlier, the instructions from Tom Wood’s Custom Driveshafts are excellent and there are numerous SYE online installation write ups and videos. For the basic breakdown of these chain-driven cases, you will need a couple of sockets and snap ring pliers.
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Yes, this can be done with the case in the truck, but it’s much easier to do it on a bench. Once the case and components are torn down to individual parts, we started to notice some worn items – nothing really bad, but alarming nonetheless.
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The high/low range shift fork was extremely worn. Ivar at Kelowna Transmission and Auto Repair has seen this many times and it’s typically caused from low fluid levels, or a malfunctioning oil pump. I suspect the pump pickup was not connected properly – great. There are no serviceable parts on the fork, so it had to be replaced.
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It was time to wash the grime and goo out of the case internals. A Varsol tank quietly sits in the corner of my shop. It’s nasty stuff and requires a mask, goggles and gloves. Safety third, right? If you don’t have access to a cleaning tank, an engine degreaser and a scrub brush work just fine.
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With parts clean and dry, inspecting the drive chain for wear was essential. Cracks in chains and sloppy links can occur, but more common is just a plain, worn-out chain. I like to hold the chain out horizontally off of a worktable to see how much droop there is. This chain is still acceptable. If you find yourself needing a new chain purchase a Morse chain unless you like repairing destructive carnage every few months.
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Nothing obvious showed up during the remainder of the inspection. The bearings were cleaned and checked (do NOT use compressed air to dry them out) for excessive wear or any sort of a grinding or rough feel. All shift shafts and fork pads appeared to be in great shape.
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Changing all the seals is a simple and easy job. Simply pry the old seals out, clean the mating surfaces and install the new seals. The coating on the new seals (this one in red) provide an oil tight seal provided you have the surface smooth and clean. I happen to have a press, but a block of wood and a hammer work as well. Take your time. You only get one shot at it.
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Onto the bearing swapping and arguably the most difficult part of the whole procedure of installing the SYE into the transfer case. The main shafts seen in the picture (the old one is behind and the new one from Tom Wood’s is in the front) are identical in their center sections, despite the synchro assembly still remaining on the old one. The top portions of the shaft are where a pocket or a Torrington bearing rides and the new one requires a different bearing.
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The bearing to be replaced is located inside the planetary gear section and needs to be removed along with the backing cup if it is equipped. There are many ways to remove them including with the use a pocket bearing puller or you can weld a tab and use a slide hammer. You can even cut it out with a die grinder but be careful not to nick the mounting surface. With the transfer case out of the truck, I simply tapped the bearing cup out with a hammer but remember to take a measurement first!
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It’s from the input bearing side that I will tap out the bearing and sealing cup. The first thing to do is measure how deep the end of the bearing cup is.
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The old bearing and cup are on the right. They are two separate pieces. The new setup includes a spacer sleeve already on the new bearing and the cup is an integral part of the assembly. This means you don’t have to reinstall the old cup, but we will just for added leakage protection. Remember, the assembly is only a light press fit and can easily be tapped in place to match the depth measurement you took before. Do not tap against the back of the bearing – just around the outer face to keep it from deforming.
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Once the bearing is in place, you can continue on with clearing the hot mess of parts strewn across the workbench and placing everything back into the case. Or be like me and find a few stray parts and have to pull it all apart again while the sealant is setting up. Good times.
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With the case completely back together, shift the transfer case through its ranges and make sure everything works correctly before placing it back in the truck. Remember, you will need a new rear driveshaft. The 4XShaft.com website has great directions on how to measure and order a new shaft for your rig. The standard flange with the Tom Wood’s Custom Drive shafts SYE kit is the same bolt pattern as the stock front output, making flange selection much easier. I’m sure the new shafts for the Dakota will arrive any day now.
In simpler terms, this all means that we have a 2 speed, part time, manually-shifted, chain-driven transfer case with a 2.72 low range (also found on the ID tag). Other ID numbers will tell us that we have a unit from a 2000 or 2001 pickup truck.
In a vehicle with solid axles, as the suspension system cycles, the distance between the transfer case and the differential changes. Some vehicles have a slip-joint built into the center of the driveshaft, and others, like our NP241, have a slip joint (AKA slip yoke) built into the tail housing of the transfer case. For a factory vehicle with limited suspension travel, this is just fine. However, as travel increases, the slip yoke has a tendency to fall out of the back of the case, causing severe damage and leaking fluids all over the trail. It also limits the choice of joint styles for the driveshaft to a single joint attachment, which has limited travel and can hinder articulation. It’s a bit of a bummer, but it was done to keep costs low.
The Slip Yoke Eliminator kit from Tom Wood’s Custom Driveshafts is going to allow the use of a solidly mounted flange on the back side of the transfer case so we can use almost any size or type of U-joint configuration. We also have the advantage of using a longer driveshaft. This may not be that big of an issue on the Dakota, but for those of you in a short wheelbase vehicle, the added length can make a huge difference.
At the time this magazine was printed (July/2020), the SYE kit for the NP241DLD was in the $500 CAD range and comes complete with a new output shaft, bearing retainer, flange and the very important Torrington bearing and adapter sleeve that needs to be installed. The SYE installation is exactly the same as the Chevy and Dodge transfer cases with the exception of the bearing and the difficulty involved in getting the old one out.
Tom Wood includes an excellent set of instructions covering the installation. However, we wanted to give some insight with respect to this particular bearing and how to replace it.
While we had our transfer case apart, we decided to replace all the seals as well. A typical seal kit is around $60 CAD and we scooped ours from a local transmission rebuilder. Once we had the case open, there were other problems we had to address. Luckily, parts for the NP series of transfer cases made in the last 30 years are easy to source and are relatively cheap. As we opened up our “unknown history” case, we checked and replaced parts as needed to get our Tom Wood SYE kit installed and ready for the truck.
For more information visit Tom Wood’s Custom Driveshafts at www.4Xshaft.com or Kelowna Transmission and Auto Repair at kelownatransmission.com