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ok, firstly, i think this might be a good topic to put in the tech database. considering that so many people get their gears changed and yet wonder when and why they have problems with shift points, speedo calibration, and more drastically, transmission problems down the road.
so, in order to do this right and include just about all the information that needs to be said about this kind of thing, i'm taking stuff from previous posts and making kind of a "drivetrain faq," if you will.
firstly, if you are changing your gear ratio, BE AWARE that if you go to a higher gear ratio, your car will shift sooner, your speedometer will read higher, and the increments these change too will all be dependent on what gear ratio you go from, to. for instance:
if you go from 3.08s to 3.23s, you'll see a 5% difference in everything. speedo will READ 5% higher than what you are really doing, shift points will come earlier (NOT necessarily 5% earlier--that is all dependent on the car and the results can only be found out by doing the gear swap =/) and your rpms (tachometer) will read CORRECTLY, but your cruising speeds will be 5% higher rpms. if you go to a lower gear than what you had stock, everything will be opposite this.
now, concerning FIXING shift points and speedo. jetscu2000 and the slp recalibrator ONLY FIX THE SPEEDO. they say you can buy a jetscu and toy around with it and make it read that you have a different tire size and get the shift points "close" but not completely accurate. also, with the jetscu, you can only recalibrate your speedo through 2 changes of gears; for example, if your stock gears were 3.08s and you put on 3.73s, you can only set it as high as 3.42--therefore your speedo will still be off by 50%. 3.08, 3.23, 3.42, 3.73, and 4.10 are the gears that are most popular with our cars (there is also 2.73s and 4.56s, but not many people use either). so, the jetscu will only work to go from 3.08 to 3.42, or from 3.23 to 3.73. personally, unless you have a manual, these recalibrators are a waste of money. dealerships CAN reprogram a computer to a specific VIN that you might have. i know they can because i have had my pcm reprogrammed. it IS NOT illegal even though MOST dealerships will say it is and they will not do it for you. but, since 3.08s, 3.23s, and 3.42s are the only gears that come stock on any fbody, then if you get 4.10s or 3.73s, you will have to deal with the incorrect shift points and speedo. also, you can buy pcms from cars that have your gears in them as long as the donor car had the same transmission and is of the same year as your car.
as far as shift points go, i think everyone needs to be aware that possible transmission problems CAN occur when the car shifts too early or too late.
and for a reference on how to learn why it can be bad for your transmission, read here:
http://www.camarov6.com/cgi-bin/ulti...&f=23&t=001202
if i left anything important out, feel free to correct. i figure if we have something like this in the tech database, then people might understand why they are having problems with their transmission a little better and will understand what's involved with making shift points correct and with making the speedo correct.
sorry, not trying to play moderator here, i just think this could be a helpful reference in the future; and if nothing else, it can serve as an eye-opener to those who are considering a gear swap and yet know nothing about the consequences or effects of it.
:D
so, in order to do this right and include just about all the information that needs to be said about this kind of thing, i'm taking stuff from previous posts and making kind of a "drivetrain faq," if you will.
firstly, if you are changing your gear ratio, BE AWARE that if you go to a higher gear ratio, your car will shift sooner, your speedometer will read higher, and the increments these change too will all be dependent on what gear ratio you go from, to. for instance:
if you go from 3.08s to 3.23s, you'll see a 5% difference in everything. speedo will READ 5% higher than what you are really doing, shift points will come earlier (NOT necessarily 5% earlier--that is all dependent on the car and the results can only be found out by doing the gear swap =/) and your rpms (tachometer) will read CORRECTLY, but your cruising speeds will be 5% higher rpms. if you go to a lower gear than what you had stock, everything will be opposite this.
now, concerning FIXING shift points and speedo. jetscu2000 and the slp recalibrator ONLY FIX THE SPEEDO. they say you can buy a jetscu and toy around with it and make it read that you have a different tire size and get the shift points "close" but not completely accurate. also, with the jetscu, you can only recalibrate your speedo through 2 changes of gears; for example, if your stock gears were 3.08s and you put on 3.73s, you can only set it as high as 3.42--therefore your speedo will still be off by 50%. 3.08, 3.23, 3.42, 3.73, and 4.10 are the gears that are most popular with our cars (there is also 2.73s and 4.56s, but not many people use either). so, the jetscu will only work to go from 3.08 to 3.42, or from 3.23 to 3.73. personally, unless you have a manual, these recalibrators are a waste of money. dealerships CAN reprogram a computer to a specific VIN that you might have. i know they can because i have had my pcm reprogrammed. it IS NOT illegal even though MOST dealerships will say it is and they will not do it for you. but, since 3.08s, 3.23s, and 3.42s are the only gears that come stock on any fbody, then if you get 4.10s or 3.73s, you will have to deal with the incorrect shift points and speedo. also, you can buy pcms from cars that have your gears in them as long as the donor car had the same transmission and is of the same year as your car.
as far as shift points go, i think everyone needs to be aware that possible transmission problems CAN occur when the car shifts too early or too late.
and for a reference on how to learn why it can be bad for your transmission, read here:
http://www.camarov6.com/cgi-bin/ulti...&f=23&t=001202
if i left anything important out, feel free to correct. i figure if we have something like this in the tech database, then people might understand why they are having problems with their transmission a little better and will understand what's involved with making shift points correct and with making the speedo correct.
sorry, not trying to play moderator here, i just think this could be a helpful reference in the future; and if nothing else, it can serve as an eye-opener to those who are considering a gear swap and yet know nothing about the consequences or effects of it.
:D
