Anyone regeared a '97 with the SOHC? (anyone else help too please)

[yob_yeknom]

Okay, so has anyone with a '97 and the SOHC engine change gear ratios? Anyone else know what to do about fixing the speedo and all that? I have no idea if this is all the same for any other year. Here's why I ask... (all this is coming from my factory repair manual)


The 5R55E tranny (comes on models with the SOHC) on the '97 model year still uses the gear driven speed sensor on the tranny itself to send the signal to the speedometer.
Vehicle Speed Sensor (VSS)

l The vehicle speed sensor (VSS) is a magnetic pickup that sends the powertrain control module (PCM) vehicle speed information.

l The VSS sensor is mounted externally on the left-side of the transmission extension housing.

l The PCM uses VSS information to help determine electronic pressure control (EPC), shift scheduling and torque converter clutch (TCC) operation.
I'm switching from 3.55 gears to 4.10 gears and 33" tires, which will give me a close to stock final ratio. The sensor sees a faster reading due to the gear change making the driveshaft turn faster, but the tires are larger so that equals it out, so I think the speedo will be fine and that won't need anything done.

But what about this...? The Programable Speedometer/Odometer Module
Programmable Speedometer/Odometer Module (PSOM)

l The programmable speedometer/odometer module (PSOM) receives input from the rear brake anti-lock sensor. After processing the signal, the PSOM relays it to the powertrain control module (PCM) and the speed control module.

l The PSOM relays speed information to the PCM and the speed control module in miles per hour (mph).

l Information from the PSOM is used by the PCM to help determine shift scheduling, torque converter clutch operation and electronic pressure control (EPC).
How does the change affect this? The rear ABS sensor is on the axle spline, right? So it won't see a faster reading due to the gear change, but will see a slow reading since the tires are larger. Am I right about that?

So if I have 2 sensors telling the tranny when to shift gears, and one sensor reads way off the other, what's gonna happen? Or am I wrong about the whole thing?

Sorry, I'm confused...

 

[Jason_25]

Ok here's the deal.

The VSS is used in models 91-97. Although I think in 91-94s it is just used to feed the speedo/odo and nothing else.

The PSOM is what 98-01's use. It is used in place of the VSS altogether, and must be programmed by the dealer.

 

[Robert]

Jason is right. The only thing your PCM uses for speed monitoring is the VSS that is located on your transmission or transfer case if yours is 4x4. Beginning in '98 Ford uses the RABS to monitor the vehicles speed. If your final ratio is within 2% of stock then it won't benefit you to change speedometer gears. The number of teeth average around 20 teeth. If you change by 1 tooth that will change your indicated speed by 5%. If you are changing by 3% or more you could benefit from a new speedometer gear, especially since they only cost about $8.00 and take about 5 minutes to put in.

 

[ok89]

Just out of curiousity on a 98+ what would you do?

 

[Jason_25]

Originally posted by ok89
Just out of curiousity on a 98+ what would you do?

You would need to take the vehicle to a dealer and have them hook it to a computer. Be wary though, some dealers may not want to do this.

 

[Ray Lobato]

John,
My 97 had 3.55's also. When I changed from them to 4.10's and went 33's it was still off. The only reason I didn't go buy another gear is because I was going to put the AtlasII in and it uses a Heep gear, so I had to have a special speedo conversion thing made. The point was that I was still off by about 3 to 5 MPH depending on how fast I was going. 3 MPH under 55 and 5MPH going 65 and over.
You are lucky in that you can change the gear and bring it in.

 

[yob_yeknom]

So why does my Ford service manual for the '97 model year even mention the PSOM? Those quotes came directly from it, in the section where it describes what controls the 5R55E transmission. Doesn't make sense, but if it worked for Ray then that's the way it is.

 

[wpurple]

I changed the axle ratio in my 97 from 3.27 to 3.73 and just changed the VSS gear and it worked perfectly.

 

[Ray Lobato]

Originally posted by yob_yeknom
So why does my Ford service manual for the '97 model year even mention the PSOM? Those quotes came directly from it, in the section where it describes what controls the 5R55E transmission. Doesn't make sense, but if it worked for Ray then that's the way it is.

John,
That's a good question. I don't have a answer for that, all I know is that it works changing the gear works.

 

[Big Bear Bob]

what about a 98 with 31" tires and 373 gears. Would going to 410 be possible? or even worth the hastle?

 

[XLT_66]

I am wanting to get some 4:10s for my 96 V8. I have 3:73s right now and just want some more low end off the line seat of the pants type feeling... Would most people recommend gettin a shop to put them in, or could someone who has never done it before but is good at directions be able to do it? I would have a good person to go to for questions while in progress if i ran into trouble. ALso, where is the best place to get new gears....?