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68-RFE Transmission Up-Grade
There are many things that need to be understood about the RAM 68-RFE transmission. This transmission was originally designed to be very inexpensive to manufacture. This approach forced the original designers to cut corners in size and quality of materials that could be used. On a positive note, the technology that is utilized in the transmission is leading edge; this advanced technology has forced the aftermarket to completely rethink how to modify and control the transmission so that it can still perform and remain reliable while modifying the engine to have higher power levels over stock.
ATS has developed a combined technology utilizing re-calibration of the hydraulic circuits inside the transmission, including revamped accumulator rates, reprogrammed clutch to clutch apply and release timings, and line pressure rise rate to perfectly match the torque output of the engine. These enhancements, along with other key hydraulic modifications which ATS makes, must be done to ensure the clutch packs have the correct apply and release rates when commanded on or off. As well, the transmission hard parts have many limiting weaknesses which do not allow for increased power levels over stock. Specifically, the light duty shafts and hubs, and the low one-way sprag; these hard part weaknesses must be addressed.
Some of the areas that are addressed by ATS to complete the performance transmission upgrade package are listed below, starting at the front of the transmission working towards the back.
The Torque converter regulator valve has been redesigned to prevent over pressure and ballooning of the converter, along with regulating minimum converter charge for proper cooling and lubrication of the transmission gear set. This redesign also eliminates the common problematic valve and bore ware that is usually the first cause of high mileage transmission failure.
The main pressure regulator circuit is modified to enable a broader range of pressure that can be commanded from the TCM. This allows the pump to lower line pressure when the engine is at low loads and more responsively raise pressure above stock to react with increased engine torque and horse power levels.
Rotating Clutch Drum Assembly and Clutch Packs:
Clutch modifications are generally one of the most impactive and important items that can be upgraded in any transmission. In the case of the 68-RFE transmission, there is little room for additional clutches so modifications must be done to pressure plates providing increased clutch surfaces. The clutch packs that are increased surface area listed below.
The Under Drive (Forward) clutch pack surface area is increased by 21%, using single sided clutch plates.
The Over Drive clutch pack surface area is increased by 17%, also using single sided clutch plates, this allows for better clutch control when overdrive is used at higher power levels.
The 2C clutch pack surface area is increased by 34%, using double sided frictions.
The 4C clutch pack surface area is increased by 34%, using double sided frictions.
The weak mechanical low one-way sprag is replaced with a stronger roller clutch design that used a "cam and roller" system. The factory low sprag not only has a very weak torque capacity, but it also fails from lack of proper lubrication. The stronger low roller clutch design used by ATS prevents the higher mileage failure associated with the sprag-type clutch. Although the new "cam and roller" low roller clutch design is much stronger it still has imitations; the Co-Pilot transmission controller contains a direct function to route power around the mechanical clutch when extreme power levels are sensed. You will read more about this in the Co-Pilot section below.
The valve body is considered the nervous system of the transmission; the valve body is responsible for converting the electrical signals from the TCM into hydraulic actions. The 68-RFE uses a non-synchronous, clutch-to-clutch design. This means that the shifts from gear to gear must be timed perfectly thereby releasing and applying a friction clutch to achieve an flawless shift. Because of the sensitivity of the hydraulic circuits, we heavily modified many areas of the valve body. Hydraulic oil flow is ported to certain clutch packs where additional pressure is needed. The accumulator piston seals have been redesigned to ensure hydraulic pressure integrity. The accumulator plate is made of high-grade material to compensate for the additional pressure that the accumulator pistons and springs exert during heavy power situations. Also, the ATS 68-RFE valve body can be purchased separately and installed in a stock transmission for increased transmission capacity.
There are three shafts in the 68-RFE that are of some concern. The forward hub/shaft, Intermediate hub/shaft and the input shaft.
The forward hub/shaft is reinforced to eliminate breakage.
The Intermediate hub/shaft is reinforced to eliminate breakage.
The input shaft is an optional upgrade, and is made made from 300M billet material just like our 47-RE and 48-RE shafts.
Case and Pan:
The main transmission case does not require a lot of conditioning aside from a few small hydraulic modifications to allow for proper oil flow. At higher power levels the transmission case does need to be strengthened. This is a simple fix that is taken care of with the optional heavy-duty transmission pan, which was designed in part to act as a girdle, thus eliminating the flex in the case. The large over sized pan also provides for an additional 5 quarts of ATF allowing the transmission to run cooler.
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