Speedo correction
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Lexus Test Driver
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From: Sideways on the Yellow Brick Road! < Thats KS!
Speedo correction
I am still ISO inf. regarding the speedometer on my 97 SC400. How can you correct the speedometer reading once you put steeper gears in the rear end? Someone out there has had to have encountered this with all the supra LSD swaps I see in the forums. I know you can clock the car and always look at the speedo and subtract 5 to 10 mph or whatever it is, But I want the speed right, not to mention this will affect the odometer (in a bad way) in think. Any one have the answer? LMK
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Lexus Test Driver
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From: Sideways on the Yellow Brick Road! < Thats KS!
With the sensor in the tail shaft I don’t see how a different set of gears could not effect the actual speed to speed displayed ratio. Please explain if I’m not understanding this.
if the sensor is in the tail shaft, the then the spedo will be off some because the tail shaft will be turning the same speed, but since u have diffrent gears the wheels will be spinning faster or slower depending if u go taller or shorter. the tailshaft will always be spinning as fast as the tranny is spinning but since u altered the gears which spin the wheels the speed will be diffrent, unless the speed sensors are on the wheels. those are my thoughts correct me if im wrong. please.
Originally posted by audi2nr
if the sensor is in the tail shaft, the then the spedo will be off some because the tail shaft will be turning the same speed, but since u have diffrent gears the wheels will be spinning faster or slower depending if u go taller or shorter. the tailshaft will always be spinning as fast as the tranny is spinning but since u altered the gears which spin the wheels the speed will be diffrent, unless the speed sensors are on the wheels. those are my thoughts correct me if im wrong. please.
if the sensor is in the tail shaft, the then the spedo will be off some because the tail shaft will be turning the same speed, but since u have diffrent gears the wheels will be spinning faster or slower depending if u go taller or shorter. the tailshaft will always be spinning as fast as the tranny is spinning but since u altered the gears which spin the wheels the speed will be diffrent, unless the speed sensors are on the wheels. those are my thoughts correct me if im wrong. please.
Lead Lap
Joined: Feb 2002
Posts: 727
Likes: 1
From: New Jersey
I'm pretty sure the speed is output by the ECU (rather than mechanical) because the AEM has the ability to adjust for different axle ratios and tire sizes. Whether there'a any way to compensate using the stock ECU 
Racer
Joined: Feb 2001
Posts: 1,348
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From: NY/NV
On the tail section of our transmissions there is a speed sensor rotor...it looks like a gear and is installed in the output shaft of the tranny. This is an on vehicle repair. I would find out if there is a different part number for the gearing that your looking for to correct any changes you might have by installing the LSD and changing the ring gear.
The easiest thing to do is install an LSD and use the same ring gear. Thats what I did.
gadgetSC-t
The easiest thing to do is install an LSD and use the same ring gear. Thats what I did.
gadgetSC-t
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Lexus Champion
Joined: Nov 2001
Posts: 2,328
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From: PHX
Originally posted by SupraCoup3
I believe Vssc400 said that the speed sensor is on the tailshaft -- not on the wheels themselves, hence it is not effected by the steeper gearing.
John
I believe Vssc400 said that the speed sensor is on the tailshaft -- not on the wheels themselves, hence it is not effected by the steeper gearing.
John
Ok, I can't believe how retarded that post was.
Note to self, don't post at 1 AM.
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Lexus Champion
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From: PHX
how about a yellow box speed calibrator?
http://www.blackrobotics.com
knowing the gearing change you've made, you'll know the exact percentage change you need to make. This little guy intercepts your speed sensor on the tailshaft (before the diff, and speed miscalibraction dummy!) and modifies the signal before it goes back to your ECU.
It's about 100 bucks.
John
Edit: I double posted on purpose to bump this back up
http://www.blackrobotics.com
knowing the gearing change you've made, you'll know the exact percentage change you need to make. This little guy intercepts your speed sensor on the tailshaft (before the diff, and speed miscalibraction dummy!) and modifies the signal before it goes back to your ECU.
It's about 100 bucks.
John
Edit: I double posted on purpose to bump this back up
Last edited by SupraCoup3; Sep 19, 2004 at 09:33 PM.
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