More speedo gear confusion. - TCCoA Forums
 
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post #1 of 11 (permalink) Old 08-16-2006, 07:55 PM Thread Starter
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More speedo gear confusion.

Sorry this is kind of long but I don't know if my SCT tunes will conflict with my new hardware.
Which speedo gear will I need when I upgrade my drivetrain? The reason I am confused is because I had my car tuned by Jerry when he was in Georgia last year. At the time I had:
  • stock '95 4R70W (7 tooth output shaft and j-mod w/ 300HP settings)
  • 3.08 gears
  • factory speedo gear (19?)
I had him program it for 3.73's and purple speedo gear (21?) since I was planning to upgrade. So the EEC is flashed for 3.73's. The shift points are off because I still have the 3.08's and factory speedo gear.
Meanwhile, I have purchased a '99 GT 4R70W (8 tooth ouput shaft) to install when I put in the 3.73's. So I know I don't want to use the purple tooth as it will not last with the '99 tranny. I purchased a speedcal... so I can use the original speedo gear, right? Or is it only the 23 tooth that I need to avoid? Do I have to buy another program from Jerry to get the shift points right or is there another gear I can use?
I noticed that the online calculator for the speedcal does not have input for the different output shaft teeth. Does it not make a difference in the calculations?

Edit: Oops. I just realized I used the same thread title as another thread.

Last edited by tinman_72; 08-16-2006 at 08:10 PM. Reason: Duplicate thread title.
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post #2 of 11 (permalink) Old 08-16-2006, 09:08 PM
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I went through this today for my car with 4.30's and a 7 tooth transmission and a 8 tooth transmission. From what we figured out, this is what you do.

Go to the Calculator, put in the stock calculation as 3.27, 21 teeth, on the other side put in 3.73 and 19 teeth. Keep the tires the same size for both. That *should* give you the right speedcal code, but I am not entirely sure that is correct.
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post #3 of 11 (permalink) Old 08-17-2006, 08:46 AM Thread Starter
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So that should make my speedometer correct with the factory 3.08 speedo gear, but what about my shift points? Am I correct in that the speedcal only affects the speedometer and not the shift points? Am I stuck with having to buy another program for the XCal2?
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post #4 of 11 (permalink) Old 08-17-2006, 09:35 AM
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Alright....

Your program is set up for 3.73's using a 21 tooth gear and a 7 tooth output shaft. Net ratio of 3:1.

Using your factory 19 tooth gear, and an 8 tooth output shaft, you've got a 2.375:1 ratio.

So for every 100 turns of the output shaft, the tune expects to see 33.3 revolutions of the speed sensor.

With the new setup, it will see 42.1 revolutions of the speed sensor for every 100 revolutions of the output shaft.

The SpeedCal needs to modify the 42.1 revs so the EEC sees 33.3. This means a .79 correction factor. 80% will be close enough. Set the dip switches for 80%.

Mike

edit: You don't need a new tune, this will bring all of your shift points and everything where they should be. The FRPP version's instructions actually give you the percentage modification for the dip switches. If your using a Dallas unit, they just list gear ratios. For the Dallas unit, use DIP switch settings 1010000110. Hope that helps.

edit 2: I'm saying this based on the fact that you said you're going to install this with the 3.73's. It'd be different for the 3.08's obviously.

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Last edited by Toombs; 08-17-2006 at 09:49 AM.
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post #5 of 11 (permalink) Old 08-17-2006, 12:12 PM Thread Starter
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Thanks Mike. Now that you have explained it, it makes sense. One more question - how did you determine those DIP settings for the Dallas Mustang unit? It definately seems like the way Ford did it makes more sense than the cryptic way DM did it.
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post #6 of 11 (permalink) Old 08-17-2006, 12:25 PM
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Look at the instructions for the Dallas unit.....found here.

They list all of their settings in a "this gear to that gear" format. You need a .79 correction factor applied to your new setup. Pick one of the stock gears that they list, and do the math. So, first take 3.27 / .79 = 4.14. Kind of between gears. So I tried 3.08 / .79 = 3.898. Pretty close to 3.89, which is an available gear. So use the dip switch settings that you would use for going to 3.89 from a 3.08 gear. That gives you 79.1% correction factor. Make sense?

Mike

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post #7 of 11 (permalink) Old 08-17-2006, 01:11 PM Thread Starter
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That makes a lot of sense. Thank you very much.
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post #8 of 11 (permalink) Old 01-11-2007, 10:14 AM
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Toombs,

Hate to ressurect a post from the dead.....

where did you get the speed calibrator?

Does this also help to adjust the odometer to read correctly as well?

1997 LX Sport 4.6L 2.73 , MODS=SCT tuned/J-Mod/Trans Cooler/Dyno max Cat-Back/NgkPlugs/Mac cold air/March UD's/FRPP aluminumcarrier3.73's(spare for strip use)/ PI cams + PI intake manifold w/adapter plate/ Mark VIII Convertor/80mm L-Maf/70mm TB/ Mark VIII 1 piece shaft/Cobra R' wheels/ Kumhos 235/60/16 - White leather w/ blue cloth seats - white face gauges in 95 cluster
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post #9 of 11 (permalink) Old 01-11-2007, 10:49 AM
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Well, it's my understanding that the odometer is gear driven off of the speedometer. If the speedo is right, the odo should be as well. I think you may have a broken tooth on the drive gear that causes the odo to hang up. Mine will do that on occasion....the odo will stop turning for a few miles, then it'll start again and run just fine. You may be having an intermittant problem with the driven gear for the odometer.

As far as the speed-cal, they only make two that I'm aware of. Just get the one that has the right connector shape (look at the speed sensor connector on your car). I *think* it is this one....HERE.

Trust me, it'll work. Just get the one that has the right connector. Check the connector on your car to make sure, but I think it's the "D" shaped one.

Mike

edit: You could also use the Dallas unit. It has the "D" shaped connector.

edit 2: You can also buy it from Lonnie at BOC. I think the one he sells is the exact same unit as the Dallas one.

- DOHC 4.6
- 4.56 Trac-Loc
- DirtyDog Converter (3,800)
- SCT Micro Tuner from Blue Oval Chips
- 13.24 @ 103mph


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post #10 of 11 (permalink) Old 01-11-2007, 11:01 AM
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Mike,

I know that the speedo gears in the speedometer are in GREAT shape as I replaced them recently, and I swapped the entire speedo out of my 1990 SC (odometer was working in it when pulled) and it didn't make a difference.

I think that part of my problem is with that flimsy *** plastic circuit board that is on the back of the gauge cluster. but the speedo is still off, and the odometer is crap...lol

1997 LX Sport 4.6L 2.73 , MODS=SCT tuned/J-Mod/Trans Cooler/Dyno max Cat-Back/NgkPlugs/Mac cold air/March UD's/FRPP aluminumcarrier3.73's(spare for strip use)/ PI cams + PI intake manifold w/adapter plate/ Mark VIII Convertor/80mm L-Maf/70mm TB/ Mark VIII 1 piece shaft/Cobra R' wheels/ Kumhos 235/60/16 - White leather w/ blue cloth seats - white face gauges in 95 cluster
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post #11 of 11 (permalink) Old 10-11-2007, 01:09 PM
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i know this is an old post but what is recommended over the other? the ford unit or the dallas speedcal....or which one is easier to install?

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