gear change - prom change
Thread Starter
Drifting
Joined: Jan 2003
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From: Reading PA.
gear change - prom change
Will I need to have my computer chip changed since I just changed from 2:59 to 3:07s I took it for a ride on Sat. and it just didn't feel right. It seemed faster with the 2:59s Don't know if it's me or what. Guess i'll find out Sat. when I take it to the track. ANY HELP GUYS? 
Thread Starter
Drifting
Joined: Jan 2003
Posts: 1,894
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From: Reading PA.
Sorry about that CFI- EFI It's a 90 Automatic. Dumb question but fill me in on the CPU? Can I change the stuff for the speedo and where is it located on the trans? THANKS FOR ALL THE HELP
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From: The Top of Utah
Originally Posted by pipe
Sorry about that CFI- EFI It's a 90 Automatic. Dumb question but fill me in on the CPU? Can I change the stuff for the speedo and where is it located on the trans? THANKS FOR ALL THE HELP
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Drifting
Joined: May 2004
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From: Thornton Colorado
Hey CFI-EFI don't mean to hijack the thread but you seem to know alot about the new speedo gears, I recently had my 93 auto changed from 2.59 gears to 3.54's would you happen to know what number tooth gear I would need to change to to get back to accurate speedometer readings. Thanks in advance
Frank
Frank
Pro
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From: W.V.C. Utah
Originally Posted by CFI-EFI
Where the speedo change has to take place, depends on the year of the car. After 1993. the CPU, or whatever, had to be reprogrammed. On your '90, a simple swap to the proper speedo gears will do the trick. The speedo gears are in the tail housing of the trans. You retain your red 17 tooth drive gear, which saves you from pulling off the tail shaft housing. Swap your white, 36 tooth, driven gear for the green, 42 tooth, driven gear, part number, 25513049, and your VSS for part number 25007308. That will get your speedo reading correctly and probably straighten out your performance problems. No CPU attention is necessary or beneficial.
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From: The Top of Utah
Originally Posted by arrow322
Hey CFI-EFI don't mean to hijack the thread but you seem to know alot about the new speedo gears, I recently had my 93 auto changed from 2.59 gears to 3.54's would you happen to know what number tooth gear I would need to change to to get back to accurate speedometer readings. Thanks in advance
Frank
Frank
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Joined: Sep 2000
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From: The Top of Utah
Originally Posted by 88421VETTE
I also don't mean to hi jack But I just swapped gears in my 88 auto Camaro I went from 2.77's to 3.42's cna I just change the speedo gear connected to the cable insted of pulling the housing off?
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Thread Starter
Drifting
Joined: Jan 2003
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From: Reading PA.
Well I ran the car Sat. and it ran worse with the 3.07s then with the 2.59s Someone at the track told me I need to change the speedo gears (which I know) to straighten out the speedo but the guy said that's why my car isn't performing right cause the ECM picks up the MPH on the speedo and tells the trans when to shift. Is he right? Do I also need to change the govenor? THANKS FOR ALL THE HELP I'M GETTIN SLOWER INSTEAD OF GETTIN FASTER
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From: The Top of Utah
Not likely. The governor speed is based on the transmission output shaft speed. It is mechanical and independent of the VSS. Get the speedo straightened out and see what the shift points look like then.
Your "buddy" has mislead you somewhat. Your 1990 didn't come with a 4L60E transmission, which DOES rely on the ECM to tell it when to shift. Your 4L60 (no E) shifts with no ECM input. However, I believe that incorrect VSS input to the ECM is messing with the fuel and timing adjustments for the engine.
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Your "buddy" has mislead you somewhat. Your 1990 didn't come with a 4L60E transmission, which DOES rely on the ECM to tell it when to shift. Your 4L60 (no E) shifts with no ECM input. However, I believe that incorrect VSS input to the ECM is messing with the fuel and timing adjustments for the engine.
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Drifting
Joined: May 2004
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From: Thornton Colorado
Hey thanks for the info, truth be told I had forgotten all about the question and didn't notice until now that you had PM'd me. I got the info and will get the parts to fix my speedo. Once again many thanks your knowledge is greatly appreciated
Frank
Frank
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From: Melbourne Florida
Cruise-In IV Veteran
Originally Posted by arrow322
Hey CFI-EFI don't mean to hijack the thread but you seem to know alot about the new speedo gears, I recently had my 93 auto changed from 2.59 gears to 3.54's would you happen to know what number tooth gear I would need to change to to get back to accurate speedometer readings. Thanks in advance
Frank
Frank
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From: altered state
St. Jude Donor '05
Originally Posted by Fuzzy Dice
FWIW there is another route you can go...in my 93 I went from 59's to 3:73's...I had an electronic box installed which corrects the speedo...the nice part about the box is when future changes come up...I put in a Dana 44 with 3:45's and it only cost $37 to change for them...then, a month later, I went with 73's in the 44 and, again, only $37 to correct the speedo...the initial cost of the box including install was $250....
Didn't mean to get off topic.
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From: Sun city CA
I am right in the middle of installing the Dakota Digital box that can be calibrated to send the correct speed to your speedometer... Will post when it is done and let you know how it worked out... Currently running 4.30s and will be switching to 3.07s or 3.33s when we go open road racing in May... I need to be able to switch the calibration back and forth.. 3.07s are to tall for street use in my car...
Drifting
Joined: Sep 2003
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From: 1990 383 Stroker Baltimore Maryland
Originally Posted by CFI-EFI
I just wanted to know if I answered your questions and see how it worked out. I hope pipe is up and running again.
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