Turbo Action 23254 Spring/weight question

CrateCamaro · 06-23-2016, 11:50 PM

Im assuming this thing shifts off output shaft rpm so previously i had a spring and weight combination to shift at 6500 with a 2.52 low gear. If i was to change to a 2.75 low gear, the driveshaft speed would be lower at 6500rpm and make the trans shift the 1-2 at a higher rpm correct? Check my math for me and see if im even thinking correctly:

6500rpm ÷ 2.52 = 2579 output shaft speed

2579rpm output shaft speed × 2.75 = approx 7100rpm 1-2 shift

Please tell me if this sounds correct.

ss3011 · 06-24-2016, 08:39 AM

Your math is correct , but remember that the valve body shifts based on governor pressure, which is based on governor rpm, which is spun by the output shaft . Once the shift valve shifts, it takes a moment to fill the clutch circuit and actually shift the transmission . Typically a 2.75 ratio is gaining rpm quicker than a 2.52 ratio trans, so to get the same shift point (6500) you may need to lead the shift point more than with the 2.52 ratio . Also the shape of the governor curve is much steeper on the early part of a governor curve than the later part of the curve. It is not a straight line . So the way I basically calibrate a governor is to use the weight to dial in the 1-2 shift, and the spring to fine tune the 2-3 shift . If going from a 2.52 to a 2.75 ratio, you will need heavier Secondary weights, and see where that takes you , before making any changes to the secondary springs . If this is a 350 trans, do these changes in pairs , same weights, same springs, don't mix .

06-23-2016, 11:50 PM	#1
CrateCamaro Member Join Date: Nov 2007 Location: Ontario Canada Posts: 411 Likes: 1 Liked 19 Times in 7 Posts	Turbo Action 23254 Spring/weight question Im assuming this thing shifts off output shaft rpm so previously i had a spring and weight combination to shift at 6500 with a 2.52 low gear. If i was to change to a 2.75 low gear, the driveshaft speed would be lower at 6500rpm and make the trans shift the 1-2 at a higher rpm correct? Check my math for me and see if im even thinking correctly: 6500rpm ÷ 2.52 = 2579 output shaft speed 2579rpm output shaft speed × 2.75 = approx 7100rpm 1-2 shift Please tell me if this sounds correct. __________________ Tony Valerio 1968 Camaro 1700 IHRA H/CM 1701 NHRA SS/?A

06-24-2016, 08:39 AM	#2
ss3011 Senior Member Join Date: Feb 2002 Location: Southeast Michigan Posts: 885 Likes: 63 Liked 221 Times in 102 Posts	Re: Turbo Action 23254 Spring/weight question Your math is correct , but remember that the valve body shifts based on governor pressure, which is based on governor rpm, which is spun by the output shaft . Once the shift valve shifts, it takes a moment to fill the clutch circuit and actually shift the transmission . Typically a 2.75 ratio is gaining rpm quicker than a 2.52 ratio trans, so to get the same shift point (6500) you may need to lead the shift point more than with the 2.52 ratio . Also the shape of the governor curve is much steeper on the early part of a governor curve than the later part of the curve. It is not a straight line . So the way I basically calibrate a governor is to use the weight to dial in the 1-2 shift, and the spring to fine tune the 2-3 shift . If going from a 2.52 to a 2.75 ratio, you will need heavier Secondary weights, and see where that takes you , before making any changes to the secondary springs . If this is a 350 trans, do these changes in pairs , same weights, same springs, don't mix .