Switching to 3.73 Gears

[Stang_inang_yan]

I wish the 3.31 gear would fit with my Torson. I'd be much better off with my SCed car with a 3.31 than with the 3.73.

Why? I'd like to know what's up? I'm deciding on getting it. Thank you.

Sponsored

 

[Danger]

My siiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiides :lol::lol::lol::lol::lol::lol:

Lol I said shit instead of shift lol I'll leave it, not going to edit that one.:lol:

 

[Stang_inang_yan]

Actually read it as shift lol.

 

[EXP Jawa]

I wish the 3.31 gear would fit with my Torson. I'd be much better off with my SCed car with a 3.31 than with the 3.73.

The 3.31:1 gear will fit your Torsen. Its the 3.15 gear that needs a different diff case.

 

[isedawishy]

I don't think 3.31 are made avail for purchase yet. Is the BCM situation resolved yet or can a simple tune modification now resolve correcting for different gears?

 

[tjo1186]

I like the 3.55. Feel like it is a great middle of the road between performance and casual highway driving. I'm sure you'd be more than happy with the 3.73 though if that's the route you decide on.

 

[smokinzx14r]

I have been messing with tires sizes I notice my speedo is off .. So it looks like the speedo picks up it's signal for the wheel sensors ? You guys that have swap gears is your car is your speedo off ? Would this gear swap mess with the traction control or the ABS ?
I want to swap my 3.31s for either the 3.55s or 3.73 sometime down the road ..I only want to use 4 gears in the 1/4 mile and I think with a 27 or 28 tall tire in the rear I could use 3.73 ..?

With the 3.31 I have now I never use first gear around town .. Second gear works fine from a dead stop ..Doing so I have to shift a lot less and get an avg of 19 MPG in town ..

 

[gqneon]

I have 3.73 and with my blower first was useless and a lot of second too. With the blower back off the car is a good gear set for NA. Otherwise without the right tires it's too much.

Tapatalk spelling errors inside!

 

[foghat]

I have 3.73 and with my blower first was useless and a lot of second too. With the blower back off the car is a good gear set for NA. Otherwise without the right tires it's too much.

Tapatalk spelling errors inside!

What kind of blower? I'd think the 3.73s would compliment a centri nicely?

 

[EXP Jawa]

I have been messing with tires sizes I notice my speedo is off .. So it looks like the speedo picks up it's signal for the wheel sensors ? You guys that have swap gears is your car is your speedo off ? Would this gear swap mess with the traction control or the ABS ?
I want to swap my 3.31s for either the 3.55s or 3.73 sometime down the road ..I only want to use 4 gears in the 1/4 mile and I think with a 27 or 28 tall tire in the rear I could use 3.73 ..?

With the 3.31 I have now I never use first gear around town .. Second gear works fine from a dead stop ..Doing so I have to shift a lot less and get an avg of 19 MPG in town ..

Of course your speedo is off. The sensor is simply counting how many times a signal passes it, and it calculates a speed based on that. It is calibrated to do that based on specific assumptions - including set values for tire size and gear multiplication. If you change that, you have to also change the factor by which it calculates. It used to be that you changed the number of teeth on the speedo drive gear. Now, its a reflash with a tuner.

The speed signal may come off of the wheel sensors, but traditionally a lot of RWD cars have used a pick up on the transmission. Old mechanical drive cables were replaced by electronic sending units in the same location years ago. However, I had an Aerostar that used the rear center ABS sensor for the speed signal, so it does vary. But at the end of the day, the ABS system has its say in the matter - it is looking for specific wheel rate of rotation at specific vehicle speed, within a certain window.

If the rate of rotation is outside that window, then either a wheelspin or brake lock-up event is occurring, and the system needs to react. If that occurs for a prolonged time (continuously), then it will fault out, assuming that some sort of error has occurred. Or at least that's the case with my car. I'm going to assume that the programming has gotten more sophisticated, but it is still going to be bound to a window of acceptable variation from wheel to wheel.

If you change gear ratio so that the reported wheel speeds are outside the window compared to the reference speed, then you're still going to have this issue. On automatic transmission cars, this also ties to the shift programming, since the PCM handles that. If the measured road speed is outside of where it should be for the engine speed / gear combination, it could also lead to a fault.

You can potentially bring the system back in line by changing the tire height to account for the gear ratio change, but that sort of defeats the purpose. By doing so, you'll bring the overall effective gearing back to where it was before. Its like how offroaders go to shorter axle gears to compensate for the taller tires. The overall system reduction remains the same, but with more axle clearance. The same thing would apply here, so there's no point in going through the effort unless you liked the look of the taller tire.

But at the end of the day, if you change gear ratios or tire size, you should have the car reflashed to make up for the difference. It'll not only make your chassis controls operate properly and correct your speedo, it'll also correct your odometer so that you don't appear to roll miles up too fast.

 

[FivepointOHYEAH]

Of course your speedo is off. The sensor is simply counting how many times a signal passes it, and it calculates a speed based on that. It is calibrated to do that based on specific assumptions - including set values for tire size and gear multiplication. If you change that, you have to also change the factor by which it calculates. It used to be that you changed the number of teeth on the speedo drive gear. Now, its a reflash with a tuner.

The speed signal may come off of the wheel sensors, but traditionally a lot of RWD cars have used a pick up on the transmission. Old mechanical drive cables were replaced by electronic sending units in the same location years ago. However, I had an Aerostar that used the rear center ABS sensor for the speed signal, so it does vary. But at the end of the day, the ABS system has its say in the matter - it is looking for specific wheel rate of rotation at specific vehicle speed, within a certain window.

If the rate of rotation is outside that window, then either a wheelspin or brake lock-up event is occurring, and the system needs to react. If that occurs for a prolonged time (continuously), then it will fault out, assuming that some sort of error has occurred. Or at least that's the case with my car. I'm going to assume that the programming has gotten more sophisticated, but it is still going to be bound to a window of acceptable variation from wheel to wheel.

If you change gear ratio so that the reported wheel speeds are outside the window compared to the reference speed, then you're still going to have this issue. On automatic transmission cars, this also ties to the shift programming, since the PCM handles that. If the measured road speed is outside of where it should be for the engine speed / gear combination, it could also lead to a fault.

You can potentially bring the system back in line by changing the tire height to account for the gear ratio change, but that sort of defeats the purpose. By doing so, you'll bring the overall effective gearing back to where it was before. Its like how offroaders go to shorter axle gears to compensate for the taller tires. The overall system reduction remains the same, but with more axle clearance. The same thing would apply here, so there's no point in going through the effort unless you liked the look of the taller tire.

But at the end of the day, if you change gear ratios or tire size, you should have the car reflashed to make up for the difference. It'll not only make your chassis controls operate properly and correct your speedo, it'll also correct your odometer so that you don't appear to roll miles up too fast.

So what you are saying is that i can adjust the tires and rear end ratio and disconnect my battery, then reconnect and the computer will adjust acoordingly to these new changes?

 

[foghat]

Of course your speedo is off. The sensor is simply counting how many times a signal passes it, and it calculates a speed based on that. It is calibrated to do that based on specific assumptions - including set values for tire size and gear multiplication. If you change that, you have to also change the factor by which it calculates. It used to be that you changed the number of teeth on the speedo drive gear. Now, its a reflash with a tuner.

The speed signal may come off of the wheel sensors, but traditionally a lot of RWD cars have used a pick up on the transmission. Old mechanical drive cables were replaced by electronic sending units in the same location years ago. However, I had an Aerostar that used the rear center ABS sensor for the speed signal, so it does vary. But at the end of the day, the ABS system has its say in the matter - it is looking for specific wheel rate of rotation at specific vehicle speed, within a certain window.

If the rate of rotation is outside that window, then either a wheelspin or brake lock-up event is occurring, and the system needs to react. If that occurs for a prolonged time (continuously), then it will fault out, assuming that some sort of error has occurred. Or at least that's the case with my car. I'm going to assume that the programming has gotten more sophisticated, but it is still going to be bound to a window of acceptable variation from wheel to wheel.

If you change gear ratio so that the reported wheel speeds are outside the window compared to the reference speed, then you're still going to have this issue. On automatic transmission cars, this also ties to the shift programming, since the PCM handles that. If the measured road speed is outside of where it should be for the engine speed / gear combination, it could also lead to a fault.

You can potentially bring the system back in line by changing the tire height to account for the gear ratio change, but that sort of defeats the purpose. By doing so, you'll bring the overall effective gearing back to where it was before. Its like how offroaders go to shorter axle gears to compensate for the taller tires. The overall system reduction remains the same, but with more axle clearance. The same thing would apply here, so there's no point in going through the effort unless you liked the look of the taller tire.

But at the end of the day, if you change gear ratios or tire size, you should have the car reflashed to make up for the difference. It'll not only make your chassis controls operate properly and correct your speedo, it'll also correct your odometer so that you don't appear to roll miles up too fast.

So what you are saying is that i can adjust the tires and rear end ratio and disconnect my battery, then reconnect and the computer will adjust acoordingly to these new changes?

I don't think that is what he is saying at all. You need to reflash your car with a flash that takes into account your different gearing/tire size.

 

[EXP Jawa]

So what you are saying is that i can adjust the tires and rear end ratio and disconnect my battery, then reconnect and the computer will adjust acoordingly to these new changes?

Uh, no. Your car's PCM has no idea that you changed anything. The only thing that disconnecting the battery will do is wipe out the radio stations on your radio, and, I suppose any MIL's that you might happen to have. But it'll have no bearing on the gear change or your speedo. I'm not sure where you got that idea.

You have to use a tuner, and reflash the computer with an updated program that accounts for the change and gives the computer a new factor to calculate your speed with. You can probably also have a Ford dealer do it for you - my father did that when he put oversized tires on his F-150 - but maybe you don't want them to know...

 

[smokinzx14r]

Uh, no. Your car's PCM has no idea that you changed anything. The only thing that disconnecting the battery will do is wipe out the radio stations on your radio, and, I suppose any MIL's that you might happen to have. But it'll have no bearing on the gear change or your speedo. I'm not sure where you got that idea.

You have to use a tuner, and reflash the computer with an updated program that accounts for the change and gives the computer a new factor to calculate your speed with. You can probably also have a Ford dealer do it for you - my father did that when he put oversized tires on his F-150 - but maybe you don't want them to know...

That is all well and good but this is not your dads F150 ... The new Mustang can't be changed with a tune at this point .. The programmers that are out there right now can't adjust for tire size or gear ratio .. Talking to Ford about it they say there IDS tool will not do it either on the 2015 Mustang .. I'm sure in time the aftermarket tuners and ford will be able to do it ...I hope ...

I'm not buying taller tires for looks .. This is for the drag strip and for that reason you want more tire contact patch and that comes by way tire size ..Short tires don't react well on a drag strip .. So jumping to a 28 or 29 tall tire is the way to go ..The draw back is it kills your gearing , and so the need to change the gearing ..

 

[isedawishy]

A tune alone won't correct it. Everyone is working on a solution...

Sponsored