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Speedometer correction

venuspie1

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I've searched with no luck. I'm looking to swap out my current 8.8 with a 3.08 to a 8.8 with a 3.55. My truck is a 95 and the donor rear came out of a 94. How am I going to correct the speedo?

Both rears have a sensor and a tone ring with the ring gear. Do I swap those? Back when I messed with mustangs years ago, we changed the plastic gear on the cable but I'm not sure with this electronic speedo. Any help? Thanks
 


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Bgunner

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My credo
If it's not broken Don't Fix It!
You change the speedometer gear in the trans, right where the cable connects. This will allow you to correct the speedo for the new gears.

IIRC in the tech section you may be able to find a lot more info on this subject.
 

RonD

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+1^^^^

Up thru 1997, Ranger's used regular speedometer gear setup as used since the 1940s, tail shaft of transmission or if 4x4 output shaft of transfer case
So when you change rear axle ratio or rear tire diameter you can swap the driven gear out for one with more or less teeth

The Sensor on the rear axle was added for Rear ABS, nothing needs to be done if you change axle ratios or tire size, ABS just kicks in if there a sudden change, i.e. wheel lock up, it has no calibration
In 1998-2000 Ford high jack this sensor in Rangers to use for the speedometer signal
 

venuspie1

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Great! Thanks for the info. I was thinking rangers stopped using the gear in the side of the trans in 95. Any idea where to find what gear I need to change from a 3.08 to 3.55? A chart somewhere??
 

RonD

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Google: ford speedometer gear calculator

Your Ranger has a 7 tooth DRIVE gear

You will need to know your tires diameter OR Revs/mile, look here: https://tiresize.com/calculator/
 

venuspie1

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Perfect! I was actually googling this when you replied. Thanks for your help.
 

97Ranger3.0

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+1^^^^

Up thru 1997, Ranger's used regular speedometer gear setup as used since the 1940s, tail shaft of transmission or if 4x4 output shaft of transfer case
So when you change rear axle ratio or rear tire diameter you can swap the driven gear out for one with more or less teeth

The Sensor on the rear axle was added for Rear ABS, nothing needs to be done if you change axle ratios or tire size, ABS just kicks in if there a sudden change, i.e. wheel lock up, it has no calibration
In 1998-2000 Ford high jack this sensor in Rangers to use for the speedometer signal
So just to confirm, this is true even for Rangers that don't use a speedometer cable but have the speed sensor on the transfer case? Reason I'm asking is I have a 97, it doesn't have a speedometer cable, and for some reason I was under the impression the gear setup was only for the cable style.
 

RonD

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So just to confirm, this is true even for Rangers that don't use a speedometer cable but have the speed sensor on the transfer case? Reason I'm asking is I have a 97, it doesn't have a speedometer cable, and for some reason I was under the impression the gear setup was only for the cable style.
Yes, 1995 to 1997 still had the gear drive but without speedometer cable hooked up

Around 1986 Rangers started to get the speedometer cable drive WITH VSS(vehicle speed sensor) added, seen here: https://www.therangerstation.com/tech_library/images/speedsensor.gif
The VSS signal was used for the computer, and eventually Cruise control and automatic trans shifting

Rangers lost speedometer cable after 1994, but Ford used the same unit up thru 1997, just has an open space where cable could go

So up thru 1997 speed calibration was done manually by changing Driven Gears

After that speed calibration was done by software
In 1998 Rangers didn't have a "speed VSS", in 1998-2000 Rangers used the rear axle ABS sensor, also a VSS, for ABS and Speed, but the rear axle VSS has the wrong Pulse Per Mile(PPM) for a "speed" signal, Ford uses 8,000ppm
So there was software added to the GEM module to calibrate rear axle PPM to 8,000ppm
1998-2000 GEM is programmable for tire size, axle ratio doesn't matter because signal is after the ratio, VSS counts axle rotations not drive shaft rotations, so only tire size matters

2001 Rangers got the OSS(output shaft speed) sensor, always on the transmission, 2wd or 4x4, so transfer cases didn't have "speed sensors" holes from 1998 and up
OSS only goes to the computer, and then computer has the axle ratio and stock tires size to calculate the correct 8,000ppm signal and sends that out to speedo/odo and cruise
4low speed change is done in the computer as well, it does the ratio conversion for low range when the 4x4 Controller "tells it" transfer case is in 4L

Computer is programmable for axle ratios and tire size
 
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97Ranger3.0

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Yes, 1995 to 1997 still had the gear drive but without speedometer cable hooked up

Around 1986 Rangers started to get the speedometer cable drive WITH VSS(vehicle speed sensor) added, seen here: https://www.therangerstation.com/tech_library/images/speedsensor.gif
The VSS signal was used for the computer, and eventually Cruise control and automatic trans shifting

Rangers lost speedometer cable after 1994, but Ford used the same unit up thru 1997, just has an open space where cable could go

So up thru 1997 speed calibration was done manually by changing Driven Gears

After that speed calibration was done by software
In 1998 Rangers didn't have a "speed VSS", in 1998-2000 Rangers used the rear axle ABS sensor, also a VSS, for ABS and Speed, but the rear axle VSS has the wrong Pulse Per Mile(PPM) for a "speed" signal, Ford uses 8,000ppm
So there was software added to the GEM module to calibrate rear axle PPM to 8,000ppm
1998-2000 GEM is programmable for tire size, axle ratio doesn't matter because signal is after the ratio, VSS counts axle rotations not drive shaft rotations, so only tire size matters

2001 Rangers got the OSS(output shaft speed) sensor, always on the transmission, 2wd or 4x4, so transfer cases didn't have "speed sensors" holes from 1998 and up
OSS only goes to the computer, and then computer has the axle ratio and stock tires size to calculate the correct 8,000ppm signal and sends that out to speedo/odo and cruise
4low speed change is done in the computer as well, it does the ratio conversion for low range when the 4x4 Controller "tells it" transfer case is in 4L

Computer is programmable for axle ratios and tire size
Thank you so much for that! I had previously read in a tech article somewhere on here that 95 and up Rangers need an electronic device to re-calibrate the speedometer, and I've been putting off fixing my speedometer because of that. I'm glad it'll be as simple as swapping the gear out.
 

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