Visit Geno's Garage for Truck accessories.

Depending on equipment such as tire size and axle ratio, different types of pinion gears were used, which varied based on the number of teeth the gear had, or by a color code. With the advent of electronic transmission controllers and multiplexed communications systems, the need arose to express pinion factor electronically Now, vehicle speed is obtained by reading information from a speed sensor, such as the output speed sensor found on front-wheet-drive electronic transaxles. The transmission control module uses the output speed sensor signal and the pinion factor formula to calculate vehicle speed. Rear wheel drive trucks use a tone wheel.on the rear axle ring gear for output speed, and Jeep. Grand Cherokee utilizes a wheel speed sensor. Then the antilock brake controller makes the vehicle speed calculation.

Because different tire sizes and axle ratios can come on the same vehicle, these modules need to have this information. It's important because the TCM or CAB communicate the vehicle speed value to the PCM. The PCM then broadcasts this value over the vehicle's communication bus for use by other control modules. other modules, such as the BCM, the MIC, or the SKIM use the vehicle speed input to control outputs.

As far as you're concerned, though, the electronic pinion factor is a setting you program into the appropriate controller with the DRB III' or the Diagnostic and Reprogramming Tool (DART). In effect, you are telling the controller what type of equipment is on the vehicle.

if the electronic pinion factor is not programmed correctly, the speedometer may be inoperative or inaccurate, or the ABS lamp may be illuminated on Dodge trucks and jeep. Grand Cherokee, and a DTC may be set. The ABS lamp will flash if the electronic pinion factor is not set at all.

Many of the vehicles that come into your dealership utilize the electronic pinion factor. These include model year 1992 and later passenger cars and minivans that have a 41TE transaxle, except for LH vehicles, which did not start using a programmable pinion factor until 1998, when different tire sizes became available.

Dodge trucks from model year 1998 and later use the electronic pinion factor, since they all have either the EBC2 rear wheel- or the EBC325 four wheel-antilock brake systems. And 1999 and later Jeep Grand Cherokees have the electronic idinion factor, as well.

As far as when it should be set, you should program the pinion factor after replacing the TCM on passenger cars and minivans, and after replacing the CAB on Dodge trucks and Jeep Grand Cherokee.

As stated earlier, the electronic pinion factor must be set after replacing these controllers. There are a couple of differ- ences in programming pinion factor between cars and trucks, but mostly it's making sure you select the right controller to program. You also have to keep in mind that the DRB and DART provide support for released tire sizes only. if you try to program a tire size other than what's released as original equipment, you're going to end up with problems.

For example, on trucks and Grand Cherokee, the ABS will be thrown out of calibration. Other effects of programming the wrong tire size can include the speedometer not registering the correct reading, and the vehicle would most likely have a host of other driveability problems, due to the vehicle speed value being wrong.

To program electronic pinion factor with the DRB, first make sure you have the proper SuperCard installed if you are working with a vehicle older than model year 1998. Then connect the DRB to the vehicle's data link connector, and turn the key to the "ON" position. From the main menu, select "DRB Standalone." Then select the diagnostics option for the appropriate model year of the vehicle. Next, choose the module you want to program the electronic pinion factor into. For cars and minivans, select "Transmission," and for trucks and Grand Cherokees, select "Antilock Brakes" from the Diagnostics menu. After the DRB reads the module information from the vehicle, select the "Miscellaneous" option. Under the Miscellaneous menu, choose "Pinion Factor," which may be displayed as "Tooth and Tire" on some vehicles.

Match the OEM tire size on the vehicle with one of the tire sizes displayed on the DRB III. If the actual tire size isn't supported by the OEM table, you won't be able to program the pinion factor. For passenger cars, minivans and Grand Cherokee, you only need to enter the tire size, while on Dodge trucks, you may need to enter the rear axle type along with the tire size. The option labeled "Other' allows you to enter the revolutions per mile rating of the tires, within the supported range. The "Revs per Mile" information can be found in Group 22 of the appropriate service manual, or can be obtained from the tire supplier. You can also use the DART to program the electronic pinion factor. just connect the DART to the data link connector, and select "Miscellaneous Functions" from the DART's main menu. Then select the "Pinion Factor" option. When the list comes up, enter the correct tire size and press ENTER.

Don't forget to program the pinion factor the next time you replace a TCM or a CAB on applicable vehicles. it doesn't take much time, and it is very important in order for the vehicle to operate the way it was designed.

From Bob B.

Anyhow, in the past vehicle speed only mattered to the driver, but, today it matters to ABS, transmission shift points, maintenance, engine commands and other factors quite important to drivers. The pinion factor is the electronic command that is broadcast to the TCM, (transmission control module), CAB (controller Anti-lock brakes), to the PCM (program control module) and the PCM in turn broadcasts the speed throught the vehicle oiver the PCM bus. If the pinion factor is not there or is incorrect, the ABS can signal with a light or even shut down.

All Dodge trucks since 1998 have used an electronic pinion factor. The age of the speedometer drive gear is gone. Today our Rams read the number of revolutions of the tone wheel located in the rear axle housing, reports that to the CAB and in turn to the PCM. Now, some of us want to do some changing of tires, axle ratios, wheels and so on for any number of reasons. Since 1998 the lack of a speedometer drive gear has been a thorn in the side of those who have made wheel, tire, gear changes and learned to recalculate their speed and distance to compensate. For some time the thread in the list was"...how do I correct my speedometer:. ". Aftermarket suppliers turned out corrections that may or may not communicate the correct information to all the systems in the Ram that need the correct speed information. As much as you may not like your dealer or his techs, he has the power to help you out. His diagnostic tools can reach into your Ram, locate the correct values and instill them into the intellegence of the Ram. If you have a TCM replaced, or a CAB, the pinion factor must be reset. If it is correct, chances are you are a happy camper. If not, a host of drivability problems can result.

The dealer's DRB has a range of OEM tire sizes to select, and on Rams, axle ratio may be necessary as well to set pinion factor. The DRB option "other" allows the entry of tire revolutions per mile within the DRB's supported range of selections. Many dealers are using a DART (Diagnostic and Reprogramming Tool) as well as a DRB III. Pinion factor can be set from the DART as well. Your tire supplier can advise you of the number of revs per mile your tire has. Advise your tech.