We have spent the last year increasing the power of our Cummins Ram tow and chase vehicle. A consequence of this obsession is that the stock clutch is no longer capable of applying all the available power to the ground. The last thing you want in any vehicle with a manual transmission is a slipping clutch. Replacing the clutch with a factory unit was not an option since it was never designed to handle the abuse and torque of a modified turbo diesel engine. And since changing a clutch is so labor intensive, it makes sense to upgrade to something that will last longer while you are at it. We have had good experience with ATS for diesel performance parts, so we decided to ask them what they recommend we do to eliminate our weak link.
The experienced personnel at ATS recommended a few upgrades that would ensure our truck would tow reliably no matter what engine programmer power level we used. The first recommendation was their dual disc clutch that ATS gets from the renowned South Bend Clutch. To order the clutch, you must first specify the modifications done to your truck and its intended use (like towing, drag racing, or sled pulling) and they will build a clutch (that very same day) that fits your needs exactly. The second upgrade ATS recommended was to install their ForceCool Manual Transmission Cooler. This unit ensures that the fluid in your transmission does not overheat and break down from the heavy loads placed on the gears during towing. The six speed transmissions are especially known to produce high RPMs and significant fluid churning that leads to elevated temperatures and viscosity loss.
Lastly, ATS recommended installing one of their increased capacity differential covers on the rear axle. The differential cover is nice because it strengthens the rear case with its heavy duty casting, while it also holds more fluid and has a built-in heat sink for temperature reduction.
How Did We Like The Setup?The first thing we noticed was the change in the clutch pedal feel. Engagement now occurs slightly lower in the pedal travel and is much "grabbier." After a few near stalls we got used to the new feel and were excited to see how the clutch engaged each shift under hard acceleration. We were very happy with the performance. Once again we could chirp our 35-inch tires when shifting- something that had ceased to happen long ago with the larger tires.
As for the ATS Force Cooler and Protector Differential Cover, the only change we felt was the slightly smoother gear operation from changing the fluids. These modifications are ones that you will not think about much after the installation. That is part of their beauty: not having to worry about them again. Once installed, they do their job to ensure that your truck runs just like it should through many hard miles to come.
 The South Bend DD 3250 Street...  The South Bend DD 3250 Street clutch we got, recommended by technicians known to us only as Woody and Peter, came with all the parts needed to replace our tired out stock clutch. On the left is a new clutch fork that will work with the new release bearing to disengage the clutch when the pedal is pushed. Also included are new flywheel bolts and an alignment tool. |  The clutch comes assembled...  The clutch comes assembled but needs to be disassembled in order to be installed. In the top left of the image is the new nodular iron flywheel and next to it is the pressure plate. On the bottom are the two clutch discs and the center plate. Luckily, the installation occurs one part at a time since the whole assembly together is quite heavy. |  This is a close up side view...  This is a close up side view of the clutch assembly to better illustrate how the parts fit together. On the bottom is the flywheel with the starter gear. Above the flywheel inside the dark horizontal slot is one of the clutch discs and above that is the center plate that is notched to fit with the flywheel. Next is the other clutch disc and finally the pressure plate is on top. |
 This is a view you hopefully...  This is a view you hopefully won't see very often- the back of the engine. Do a careful inspection of everything back here when the tranny is out. The most important thing to check is the rear main seal that surrounds the crank. Ours is completely dry and clean the way it should look. If there is a trail of oil, even the slightest bit coming down from the seal, then replace it. Not only will you have to remove the transmission again to fix it later, but the leak could contaminate and ruin your new clutch. |  The torsional springs seen...  The torsional springs seen here are one of the weak and problematic parts of the stock clutch disc. Their purpose is to dampen the power pulses and vibrations from the motor. Poor driving habits like lugging the engine and excessive idling can cause these to fail prematurely. Our clutch disc and torsional springs actually appear to be in decent shape for 50,000 miles. Were it not for the excessive power of our engine, this clutch would still operate properly. |  South Bend Clutch improved...  South Bend Clutch improved the strength of the clutch discs to make them more durable and impervious to abuse. And in reality, it doesn't look to us like they improved them, and instead completely redesigned them. This is probably a good thing since often OEM parts are designed with cost in mind and not ultimate performance. You can also see here the ceramic buttons that make up the friction material on the disc. Ceramic is used for its increased holding power and wear resistance. |
 Can you see an important difference...  Can you see an important difference between the old and new pressure plates, besides the color? The South Bend pressure plate has significantly more surface area. This means that the heat and forces placed on it are spread out more resulting in better wear and durability. |  The ForceCool manual transmission...  The ForceCool manual transmission cooler from ATS includes everything you see here. Since most manual transmissions do not have pumps like automatics, one is needed to force the flow through the fan/cooler unit. Once operational, the unit is designed to be totally self-controlled. A thermostat senses the temperature of the fluid and turns the unit on when needed, prolonging the life of the fluid and transmission components. |  After removing the PTO covers...  After removing the PTO covers off both sides of the transmission, the coolers are installed using the longer bolts supplied in the kit. The original covers are reused with the coolers sandwiched in between the tranny housing and the covers. The left side cooler has a fluid outlet to the pump on the bottom and an inlet from the pump on the top. On the left cooler is a thermostat that controls the system, and a drain plug. The coolers can be swapped, left to right, to fit your installation needs. |
 Mounting locations for the...  Mounting locations for the pump and fan/cooler unit are up to you. We tried to place the components places that would not be pelted by rocks and debris kicked up by the tires. ATS includes a couple extra fittings, either 90 degree or straight, so that you can choose what best fits your application. |  We found a safe place for...  We found a safe place for the fan/cooler unit under the bed, right in front of the spare tire and above the rear differential. This is not the greatest location for airflow but it is out of harm's way. If you spend more time towing and not much time in the dirt you might want to mount the unit somewhere with a better source of cool air. |  The ATS cast aluminum Protector...  The ATS cast aluminum Protector Differential Cover for AAM 14 bolt 11.5-inch rear axles (Dodge and Chevy) comes with new mounting bolts, a gasket, two magnetic drain and fill plugs, and weep hole plug. The magnetic plugs capture any metallic particles in the fluid and the capacity is increased 2.5 quarts over the stock cover. Increasing the fluid capacity keeps operating temperatures lower and provides better lubrication for your hard working gears. |
 Never again will we have to...  Never again will we have to remove the differential cover to drain the axle fluid. The three holes drilled and tapped into the ATS cover are such a simple feature that we are surprised more OEM covers do not feature this. Simply remove the drain plug to drain the fluid. Then remove the weep hole plug and fill the differential through the fill hole until fluid comes out the weep hole. Tighten all plugs and you are done. |  Never again will we have to...  Never again will we have to remove the differential cover to drain the axle fluid. The three holes drilled and tapped into the ATS cover are such a simple feature that we are surprised more OEM covers do not feature this. Simply remove the drain plug to drain the fluid. Then remove the weep hole plug and fill the differential through the fill hole until fluid comes out the weep hole. Tighten all plugs and you are done. |  |