Swapping rear gears
04-16-2008, 07:45 PM
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Swapping rear gears Is there any effect besides the obvious speedo change that swapping gears would entail? looking to lose the 3.08's in favor of some 3.73's and can simply adjust the speedo since its programmable. i realize it might impact some other functions like enable speed for the fans and cruise control, but anything else?
04-16-2008, 11:14 PM
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Your shift points would be effected, but you can just tell the computer you have a different rear gearing using LS1edit or the like. We are doing the exact same change right now (open 3.08 to posi 3.73) Just got the driveshaft back from being shortened.
04-17-2008, 06:52 PM
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Just curious why and how the shift points would be affected? How does the PCM know the car is traveling at a different rate of speed? Wouldn't the extra rate of acceleration be just like accelerating downhill in essence? As I understand it the shift points are governed by speed, say it will shift out of 1st at 40MPH. If I swap gears, it will now be doing only 35 MPH, but as far as the VSS is concerned I am still doing 40. It just got there quicker - kind of like during a burnout. I was just looking to hit the track one last time with the stock LS1/auto with 3.73s instead of the 3.08's before I yank it for a cammed LS1/6 speed. Being a cheap ***, don't want to pay to have the gear input changed. 
04-17-2008, 08:55 PM
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3.73s will be nice. I have them in my 94, with a 6 speed im about 2500rpm@75mph.
I dont think there is anyway of getting around without tuning it to read mph right. I swapped from 2.73 to 3.73 in my 4l60e 95 formula and it drove and shifted fine. Speedometere was way off but it shifted fine. The only thing i can think of that the VSS would control would be downshift, not upshift.
T56s is the way to go
run some 4.56s and tall sticky tires
I dont think there is anyway of getting around without tuning it to read mph right. I swapped from 2.73 to 3.73 in my 4l60e 95 formula and it drove and shifted fine. Speedometere was way off but it shifted fine. The only thing i can think of that the VSS would control would be downshift, not upshift.
T56s is the way to go
run some 4.56s and tall sticky tires
04-17-2008, 10:35 PM
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3.73s will be nice. I have them in my 94, with a 6 speed im about 2500rpm@75mph.
I dont think there is anyway of getting around without tuning it to read mph right. I swapped from 2.73 to 3.73 in my 4l60e 95 formula and it drove and shifted fine. Speedometere was way off but it shifted fine. The only thing i can think of that the VSS would control would be downshift, not upshift.
T56s is the way to go run some 4.56s and tall sticky tires
I dont think there is anyway of getting around without tuning it to read mph right. I swapped from 2.73 to 3.73 in my 4l60e 95 formula and it drove and shifted fine. Speedometere was way off but it shifted fine. The only thing i can think of that the VSS would control would be downshift, not upshift.
T56s is the way to go
run some 4.56s and tall sticky tires 2500RPM seems high for a 6 speed and 3.73's at 70 though? Trending Topics
04-17-2008, 11:26 PM
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http://www.f-body.org/gears/
You sure your running 3.73's? This is with a T56, right?
Still kinda curious how the downshifting would be funkified.
You sure your running 3.73's? This is with a T56, right?
Still kinda curious how the downshifting would be funkified.
04-18-2008, 04:55 AM
#9
Downshifting is based on MPH i believe. Upshifting is based on RPM.
Yeah i have f-body.org bookmarked actually and thats what i usually use. Bryan Herter tuned my PCM for 3.73s because thats what i told him i had. My GPS shows 59.4MPH @60mph on the speedo so it's gotta be right. I thought it was weird with the gear calculater too. Yup it's a T56. I need to change the rear gear oil here shortly maybe ill pop off the cover and see if there are any numbers i can check to be sure. I dont see how else the PCM would have gotten the gears calculated right.
Yeah i have f-body.org bookmarked actually and thats what i usually use. Bryan Herter tuned my PCM for 3.73s because thats what i told him i had. My GPS shows 59.4MPH @60mph on the speedo so it's gotta be right. I thought it was weird with the gear calculater too. Yup it's a T56. I need to change the rear gear oil here shortly maybe ill pop off the cover and see if there are any numbers i can check to be sure. I dont see how else the PCM would have gotten the gears calculated right.
