3:73 to 4:30 on Excursion V-10
I know there are some guys running excursion v10s on here with 4:30 gears was wondering if anyone started with 3:73s? Got a quote from a local shop for 1500 installed with factory gears in the rear an...
Forum Discussion
Tim and Amy, thank you for posting your input. It helps pinpoint where confusion might lay in trying to determine what effects, if any, a change of gear ratio might have on the truck's initial programming.
You said:
I couldn't begin to guess "why Ford did" anything, but I can post the information that Ford provided concerning the speed sensor inputs to the PCM for this vintage of Excursion.
There isn't just one VSS, there are actually three speed sensors that the PCM utilizes as inputs to make decisions about how the truck will operate.
1. The Vehicle Speed sensor, which is, as you said, mounted on the axle. Ford says that "The PCM uses the frequency signal generated by the VSS (and other inputs) to control such parameters as:
- Fuel Injection
- Ignition Control
- Transmission Shift Scheduling
- Torque Converter Clutch Operation
2. The Output Shaft Speed Sensor, or OSS, which is mounted to the transmission. Ford says that "The PCM uses the Output Shaft Speed Sensor signal to help determine:
- Electronic Pressure Control
- Transmission Shift Scheduling
- Torque Converter Clutch Operation
3. The Turbine Shaft Speed Sensor, or TSS, which senses the rotational speed of the coast clutch drum. Ford says that "The PCM uses the Turbine Shaft Speed Sensor Signal to help determine:
- Electronic Pressure Control
- Transmission Shift Scheduling
- Torque Converter Clutch Operation
So, what happens when the a different gear is installed? Now, the values of the OSS will no longer be the same as before for any given VSS frequency produced by the axle. The speedometer will not change, as long as the tires do not change, but the comparative values between the three different speed sensors that the PCM is using to determine shift scheduling, TCC operation, and even fuel injection timing are not the same as before.
I recall when this issue first came up when these trucks were new, some 13 years ago, where customers wanted to have their rear axlt ratios changed at the dealer, in the hopes of maintaining the factory warranty on their new tow vehicles. Perhaps they bought one on the lot that had the 3.73 because no 4.10's were available in the color they liked. Or whatever their reason was. More than one dealer was reported at the time to be waiting for Ford approval of such a change, due to PCM calibration issues directly relating to transmission learning and emissions control, as cited above.
I do not pretend to know why Ford does this or that. The source of the technical information above concerning the three speed sensor inputs to the PCM comes directly from Ford's Powertrain Control and Emissions Diagnostics Service Manual for the 2000 Model Year Excursion with the V10 engine.
Agreed on both counts. It was an option, and a sought after one.
You said:
tim and amy wrote:
"First, The ford Excursion does not require and PCM re-programming. On Ford trucks of this vintage, the speed sensor is located in the axle, not the transmission. There for the stator ring automatically "corrects" the ratio. This is why ford did this. It allowed them to run the same PCM software no matter what the drivetrain was built as, 2wd, 4wd, or axle ratios."
I couldn't begin to guess "why Ford did" anything, but I can post the information that Ford provided concerning the speed sensor inputs to the PCM for this vintage of Excursion.
There isn't just one VSS, there are actually three speed sensors that the PCM utilizes as inputs to make decisions about how the truck will operate.
1. The Vehicle Speed sensor, which is, as you said, mounted on the axle. Ford says that "The PCM uses the frequency signal generated by the VSS (and other inputs) to control such parameters as:
- Fuel Injection
- Ignition Control
- Transmission Shift Scheduling
- Torque Converter Clutch Operation
2. The Output Shaft Speed Sensor, or OSS, which is mounted to the transmission. Ford says that "The PCM uses the Output Shaft Speed Sensor signal to help determine:
- Electronic Pressure Control
- Transmission Shift Scheduling
- Torque Converter Clutch Operation
3. The Turbine Shaft Speed Sensor, or TSS, which senses the rotational speed of the coast clutch drum. Ford says that "The PCM uses the Turbine Shaft Speed Sensor Signal to help determine:
- Electronic Pressure Control
- Transmission Shift Scheduling
- Torque Converter Clutch Operation
So, what happens when the a different gear is installed? Now, the values of the OSS will no longer be the same as before for any given VSS frequency produced by the axle. The speedometer will not change, as long as the tires do not change, but the comparative values between the three different speed sensors that the PCM is using to determine shift scheduling, TCC operation, and even fuel injection timing are not the same as before.
I recall when this issue first came up when these trucks were new, some 13 years ago, where customers wanted to have their rear axlt ratios changed at the dealer, in the hopes of maintaining the factory warranty on their new tow vehicles. Perhaps they bought one on the lot that had the 3.73 because no 4.10's were available in the color they liked. Or whatever their reason was. More than one dealer was reported at the time to be waiting for Ford approval of such a change, due to PCM calibration issues directly relating to transmission learning and emissions control, as cited above.
I do not pretend to know why Ford does this or that. The source of the technical information above concerning the three speed sensor inputs to the PCM comes directly from Ford's Powertrain Control and Emissions Diagnostics Service Manual for the 2000 Model Year Excursion with the V10 engine.
tim and amy wrote:
Second. 4.30 gears were an option, and a highly sought after one for Excursions.
Agreed on both counts. It was an option, and a sought after one.
