Speedo Calibration
Thread Starter
Drifting
Joined: Oct 2004
Posts: 1,477
Likes: 80
From: Hawaii
Speedo Calibration
I just installed my D44 with 3.45 gears in my 93. Tried to change the Drive gear in the trans to a 15 teeth gear, then found out that the part I ordered was the wrong part. It was for a ZF6....then tried to get another one for a auto, but found out that they don't make a 15 teeth Drive gear for auto (4L60). Anyone know how to recalibrate a 4L60 for 3.45 gears?
Thanks,
Thanks,
Thread Starter
Drifting
Joined: Oct 2004
Posts: 1,477
Likes: 80
From: Hawaii
Thanks CFI EFI....thats the number I was looking for.
If anyone else does the change, just for your info....P/N 12507670 "15 Teeth" Gray Drive (worm) gear is for the ZF6 and will not fit the auto 700/4L60.
The part number (8642620) CFI-EFI gave me is the "15 Teeth" Gray Drive gear for the 700-R4. The other option is to keep the "17 Teeth" Red Drive gear, and change the Driven gear to a 45 Teeth Lt blue one p/n 25513052 to adjust the speed-o.
If anyone else does the change, just for your info....P/N 12507670 "15 Teeth" Gray Drive (worm) gear is for the ZF6 and will not fit the auto 700/4L60.
The part number (8642620) CFI-EFI gave me is the "15 Teeth" Gray Drive gear for the 700-R4. The other option is to keep the "17 Teeth" Red Drive gear, and change the Driven gear to a 45 Teeth Lt blue one p/n 25513052 to adjust the speed-o.
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Originally Posted by James93LT1
Thanks CFI EFI....thats the number I was looking for.
The other option is to keep the "17 Teeth" Red Drive gear, and change the Driven gear to a 45 Teeth Lt blue one p/n 25513052 to adjust the speed-o.
The other option is to keep the "17 Teeth" Red Drive gear, and change the Driven gear to a 45 Teeth Lt blue one p/n 25513052 to adjust the speed-o.
The 17 tooth drive gear and 45 tooth driven gear is what was spec'd for the 3.31 ratio in the G92, Z51, 1984's. I can't believe it will read very close for the 3.45 gears.
RACE ON!!!
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Le Mans Master
Joined: Apr 2000
Posts: 5,713
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From: Manassas VA
Originally Posted by CFI-EFI
Haven't we done this already? It seems like we have a couple of times.
RACE ON!!!
RACE ON!!!
Oh, I have posted about it a time or two, but I still have not corrected it. Its on a list of many things to be done but still driveable without it. I have a gps that I sit on the dash to give me the speed I am moving at. Heck, I only get to drive it about 3,000 miles a year so its not that big of a deal. But unless you tell me something different the gears are not available for a 4.09 diff. , 26in tires and a automatic. I believe I have to use something such as the dakota digital box.
Race Director
Joined: Sep 2000
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From: The Top of Utah
I HAVE answered this in the last month or two, but here you go. Use a 8642620, grey, 15 tooth drive gear, a 25513052, light blue, 45 tooth driven gear, and a 10456092 VSS. Since I don't know the original ratio, I don't know if any of these items are the same as you had, or not.
RACE ON!!!
RACE ON!!!
Le Mans Master
Joined: Apr 2000
Posts: 5,713
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From: Manassas VA
Originally Posted by CFI-EFI
I HAVE answered this in the last month or two, but here you go. Use a 8642620, grey, 15 tooth drive gear, a 25513052, light blue, 45 tooth driven gear, and a 10456092 VSS. Since I don't know the original ratio, I don't know if any of these items are the same as you had, or not.
RACE ON!!!
RACE ON!!!
CFI-EFI, Are you sure that is correct for a 4.09 ratio? Could be my bad math but I figured the 15/45 would be correct for a 3.73 diff. but I would need a 15/48 for a 4.09 which I dont believe anyone makes.
Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by 93 ragtop
CFI-EFI, Are you sure that is correct for a 4.09 ratio? Could be my bad math but I figured the 15/45 would be correct for a 3.73 diff. but I would need a 15/48 for a 4.09 which I dont believe anyone makes.
a 27" tire. Since the 45 tooth drive gear is as big as they make, you will be "stuck" with about a 3-4% error. Close enough?
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Race Director
Joined: Jun 2001
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From: Marlboro country MA
As a general solution to speedo changes, consider the Abbott Electronic Ratio Adaptor from Abbott Enterprises. I have one, and my speedo is exactly on the money, as determined by my GPS.
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Let's see. What would be the more popular choice? A $150.00 electronic "black box" that you have to figure out where to mount, or a speedo gear that carries a $5.95 list price? The speedo gear will take less time to install than the mounting of the box. Wiring, dip switch setting, calibration time, all extra. Except in the case of non-factory rear end ratios, the factory speedo gearing is available, so accuracy isn't an issue in most cases.
93 ragtop reports having a GPS. Hopefully he'll report back as to the accuracy of my suggested set up. I am thinking I am exaggerating the error of those gears. What is the tolerance of the GPS measurements?
RACE ON!!!
93 ragtop reports having a GPS. Hopefully he'll report back as to the accuracy of my suggested set up. I am thinking I am exaggerating the error of those gears. What is the tolerance of the GPS measurements?
RACE ON!!!
Le Mans Master
Joined: Apr 2000
Posts: 5,713
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From: Manassas VA
As soon as I get my car back together I will let you know how the gear does. I may be off slightly more, I have 285/40/17 tires. The height may be 25.7
One other point on the electronic box is if you do go that way look at dakota digital. I believe it was around $70.00 when I priced it.
Personally I would rather do the gears then cut the wiring. If I get between 3-5 % accuracy ill be happy. Thanks again for the gear info.
One other point on the electronic box is if you do go that way look at dakota digital. I believe it was around $70.00 when I priced it.
Personally I would rather do the gears then cut the wiring. If I get between 3-5 % accuracy ill be happy. Thanks again for the gear info.
Large Impressive Member
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
James, did you sell my old rear end yet? The reason I'm asking is that someone contacted me asking if I still had my 36. I told him it was recently for sale again but I didn't know anything past that. I also mentioned the shipping costs involved to return it to the mainland! 
Don't forget to post new ET results! 
Don't forget to post new ET results!
Le Mans Master
Joined: Apr 2000
Posts: 5,713
Likes: 105
From: Manassas VA
Originally Posted by pole-shed
I need a gear for a 355 rear automatic . Do I use the red one?
This is the info I have from a 2000 tpis catalog.
For the drive gear you need the grey one which has 15 teeth. part no. 8642620.
For the driven gear you need a 42 tooth for a 26 in tires part no. 25513049 (green gear)
or
a 43 tooth for a 25.7 in tire. part no. 25513050 (purple gear)
Now the sensor that the wire plugs onto and the driven gear rides in may have to be replaced as well depending on what you have now.
CFI-EFI may add to this as he seems to be very much up on the info with these gear changes.