tranny gov shift ?

junior barns · 08-14-2009, 05:06 PM

I have a rossler with auto 1-2 shift the gov was set to shift at 5800 with a 275 low gear.

what will this gov shift at with a 252 low gear??? Would have asked mr. rossler but they are closed til monday!!

Thanks in advance!

Tony Curcio · 08-14-2009, 07:04 PM

I never thought about it before, but I think it's a mathematical equivalency equation.

2.52 is .916 of 2.75, which means the output shaft is turning that much slower. So now the engine has to turn that much faster to get the governor spinning fast enough to make the shift. Divide 5800 by .916, you get 6330.

That's an educated guess. Please let me know what you find out for sure.

ss3011 · 08-14-2009, 07:15 PM

The governor shifts the tranny based on the output shaft rpm. That rpm will be the same but because the first gear ratio is 2.5 compared to 2.75. The engine will be turning slower at the shift point.

Tony Curcio · 08-14-2009, 07:16 PM

Wait, I think I got it backward. The numerically lower gear makes the output shaft spin faster at a given engine rpm, so you multiply 5800 by .916 and get 5312.

Tony Curcio · 08-14-2009, 07:18 PM

Looks like we were posting at the same time. This was good mental exercise after a brutal day.

ss3011 · 08-14-2009, 07:26 PM

Plus as we shift lower and lower in rpm, the converter will be slipping more, so while the shift point to the output shaft rpm stays the same, the shift point to engine rpm will be different.

Bill Grubbs · 08-14-2009, 08:33 PM

Don't forget to accout for the difference in acceleration rate. Theoretically it will shift at the same output shaft RPM. However the springs are affected by not only the RPM, but also the rate of acceleration.

I actually have the data on the computer from tests done in 2006, but it is not handy right now.

Bill

Found it 2.75 to 2.52 showed a 225 RPM rise in actual shift points. (Caveat...I believe it was the same springs and weights but I cannot find the setup book and therefore I cannot be 100% sure)

junior barns · 08-29-2009, 09:15 PM

Bill your records were spot on! Saw a 300 rpm increase in the shift point using the same gov!!

Thanks for all the replies

08-14-2009, 05:06 PM	#1
junior barns Senior Member Join Date: Jun 2006 Posts: 541 Likes: 11 Liked 20 Times in 14 Posts	tranny gov shift ? I have a rossler with auto 1-2 shift the gov was set to shift at 5800 with a 275 low gear. what will this gov shift at with a 252 low gear??? Would have asked mr. rossler but they are closed til monday!! Thanks in advance!

08-14-2009, 07:04 PM	#2
Tony Curcio Member Join Date: Mar 2002 Location: West Chester, PA Posts: 271 Likes: 1 Liked 4 Times in 1 Post	Re: tranny gov shift ? I never thought about it before, but I think it's a mathematical equivalency equation. 2.52 is .916 of 2.75, which means the output shaft is turning that much slower. So now the engine has to turn that much faster to get the governor spinning fast enough to make the shift. Divide 5800 by .916, you get 6330. That's an educated guess. Please let me know what you find out for sure. __________________ Tony Curcio 1860 STK

08-14-2009, 07:15 PM	#3
ss3011 Senior Member Join Date: Feb 2002 Location: Southeast Michigan Posts: 908 Likes: 70 Liked 238 Times in 113 Posts	Re: tranny gov shift ? The governor shifts the tranny based on the output shaft rpm. That rpm will be the same but because the first gear ratio is 2.5 compared to 2.75. The engine will be turning slower at the shift point.

08-14-2009, 07:16 PM	#4
Tony Curcio Member Join Date: Mar 2002 Location: West Chester, PA Posts: 271 Likes: 1 Liked 4 Times in 1 Post	Re: tranny gov shift ? Wait, I think I got it backward. The numerically lower gear makes the output shaft spin faster at a given engine rpm, so you multiply 5800 by .916 and get 5312. __________________ Tony Curcio 1860 STK Last edited by Tony Curcio; 08-14-2009 at 07:19 PM. Reason: added "at a given engine rpm"

08-14-2009, 07:18 PM	#5
Tony Curcio Member Join Date: Mar 2002 Location: West Chester, PA Posts: 271 Likes: 1 Liked 4 Times in 1 Post	Re: tranny gov shift ? Looks like we were posting at the same time. This was good mental exercise after a brutal day. __________________ Tony Curcio 1860 STK

08-14-2009, 07:26 PM	#6
ss3011 Senior Member Join Date: Feb 2002 Location: Southeast Michigan Posts: 908 Likes: 70 Liked 238 Times in 113 Posts	Re: tranny gov shift ? Plus as we shift lower and lower in rpm, the converter will be slipping more, so while the shift point to the output shaft rpm stays the same, the shift point to engine rpm will be different.

08-14-2009, 08:33 PM	#7
Bill Grubbs Member Join Date: Oct 2002 Location: Magnolia, Texas Posts: 416 Likes: 3 Liked 564 Times in 66 Posts	Re: tranny gov shift ? Don't forget to accout for the difference in acceleration rate. Theoretically it will shift at the same output shaft RPM. However the springs are affected by not only the RPM, but also the rate of acceleration. I actually have the data on the computer from tests done in 2006, but it is not handy right now. Bill Found it 2.75 to 2.52 showed a 225 RPM rise in actual shift points. (Caveat...I believe it was the same springs and weights but I cannot find the setup book and therefore I cannot be 100% sure) Last edited by Bill Grubbs; 08-14-2009 at 08:42 PM.

08-29-2009, 09:15 PM	#8
junior barns Senior Member Join Date: Jun 2006 Posts: 541 Likes: 11 Liked 20 Times in 14 Posts	Re: tranny gov shift ? Bill your records were spot on! Saw a 300 rpm increase in the shift point using the same gov!! Thanks for all the replies Last edited by junior barns; 08-29-2009 at 09:15 PM. Reason: spelling