Up to Standards
- Author: Mike Weinberg, Contributing Editor
- Subject Matter: Transfer case
- Units: BW 44-44, 44-45
- Vehicle Application: RAM truck
- Issue: Design & operation
Looking at the BorgWarner 44-44 and 44-45 transfer cases, we see an evolutionary change that started with the BW4405 and 4411 and has now reached this level of development. The design uses a wet-clutch pack in the transfer case to split torque between the rear and front axles.
The BW 44-44 is an “active” full-time transfer case. This unit has five operational ranges : 2 High, 4WD Auto, 4WD Lock, Neutral and 4WD Low. The driver accesses all operating ranges via a dash-mounted selector switch. The position of the selector switch informs the Drive Train Control Module (DTCM) which range the driver wishes to use. The DCTM will use info from the transfer-case mode sensor and from the bus from the TIPM (Totally Integrated Power Module) to see whether the parameters are correct to enable a shift. The electronic shift motor/encoder will then shift the unit into the selected gear.
In 2 High all torque is flowing to the rear axle. In 4WD Auto, the DTCM will send torque to the front axle automatically in response to differences in wheel speeds without any input from the driver. This mode can be used all the time even on dry pavement. 4WD Lock engages the clutch pack to lock the transfer case in a 50/50 torque split front to rear and should be engaged only in off road conditions or snow, ice, sand or other conditions that let the wheels slip to cancel out driveline windup and crow hop. 4WD Low provides a 2.64-1 gear reduction for off-road use only.
The BW 44-45 transfer case is identical to the 44-44 but operates as an electronically controlled part-time transfer case with SOF (shift on the fly) capability. The operation is the same except for the control system, which has only four operating ranges: 2 High, 4WD Lock, Neutral and 4WD Low. The control system is not active so there is no 4WD Auto position. These units are found in Dodge RAM 1500, 2500 and 3500 trucks from 2011 up. This is interesting, as Chrysler had used transfer cases built by New Process Gear, which was owned by Chrysler, forever. New Process Gear which was in Syracuse, N.Y., morphed into New Venture Gear, a 10-year joint venture with GM that collapsed under its own weight of using terrible Getrag designs for manual transmissions. Magna Powertrain, a huge Tier 1 OEM supplier, took over New Process/New Venture and continues to manufacture transfer cases in Mexico.
The design is one that every technician should have seen by now. It hasn’t changed much from the BW 44-05, with a ball-and-ramp clutch application. Usually the assembly issues come from assembling the clutch pack incorrectly or having improper clutch clearances, which should be 0.039-0.059 inch. The usual tech calls result from what has now become very sophisticated electronic control systems. There have always been issues with failed or corroded harnesses and motor problems. The motor/encoder has a complex internal planetary-gear reduction system that make a low-torque rapid motor into a slower high-torque motor for shifting the transfer case and applying a huge amount of torque to the internal clutch pack. The motor is rated at 20 amps and operates on 14 volts. All the computer inputs will be five volts. The computer is capable of throwing about 40 C and U codes. As usual there are 75 pages on the repair manual and 111 pages on electrical diagnosis.
Here is where these units get interesting. For longer than I care to remember I have been speaking with technicians about the importance of tire sizes on 4WD and all-wheel-drive vehicles. Possession of a stagger gauge, which is a large caliper, to read tire circumference directly is a must. They are cheap – we sell a good one for around $50 – and they save a lot of wasted labor and diagnostic frustration. I no longer have to worry about it because RAM and I am sure other manufacturers have programmed this into the TIPM (Totally Integrated Power Module) and assigned a trouble code to it: C1078, Tire Revolutions Range Performance. The DTC will set if the STORED tire size is different from that which the TIPM gets from the wheel-speed sensors.
I have included here a chart of the production tires that are pre-programmed into the TIPM. RAM has a specific note that states: “A non-production tire size cannot be programmed into the TIPM. The production Powertrain, with the production size tires, is the only emissions certified configuration that is available for reprogramming.”
This means that a truck with tires of an incorrect size, such as oversized off-road tires, or mismatched tires for size or pressure will generate a C1078 code, and in states that do emissions testing this vehicle will fail. Now I am sure in the future some geek will figure out how to reprogram for other-size tires, but be aware of how critical it is on these vehicles to have a matched set of tires and pressures that meet the standards now in the computer. Every time you take in a vehicle with 4WD or AWD, you need to measure tire sizes and pressures before you go any further. All tires must be within one-quarter inch in circumference and be inflated to the same pressures. On 2011-and-up RAM trucks with a 44-44 transfer case, the tires have to be one of those specified on the chart for proper code-free operation. The next order of business is to make a deal with a local tire distributor so you can add a set of tires to the repair order.
Mike Weinberg is president of Rockland Standard Gear.
