Correct Shift Point

njk53 · 05-02-2010, 01:32 PM

I have talked to different people on this subject and received different answers. Maybe someone can help. For example: Your car has a big block Chevy engine and it makes a peak 450 lb/ft of torque at 3200 rpm and 440 HP at 5700 rpm. The car has a 350 turbo hydamatic. At what engine rpm should your 1-2 shift be? 2-3 shift be?

Phillip marvetz · 05-02-2010, 02:04 PM

Depends on the converter stall.

Adger Smith · 05-03-2010, 07:58 AM

At the RPM that makes the quickest E.T. Pick some shift points and try testing your car instead of talking to people. If you listen the car will tell you what it likes.

njk53 · 05-03-2010, 08:41 AM

Adger, where would you suggest as a starting point? The car is new to us and the previous owner never said where the shift points were. I have been having a hard time getting in touch with him. Car has a 4800 stall converter.

buzzinhalfdozen · 05-03-2010, 09:58 AM

Take Adgers advice, try a few different points. He's right the car will let you know what it wants, that plus the E.T. slip. Joe

Phillip marvetz · 05-03-2010, 10:18 AM

With that 4800 stall I would start shifting at 5800 then try a little higher each run until it slows down. Lot of guys are guilty of revving there engines to high, just because it will turn 7000 doesn't mean it is fast there.

junior barns · 05-03-2010, 10:39 AM

looking at yiour pk torque number, I think your converter stall may be to high?? I would start at 5500 on my shift and go from there with what you have.

Adger Smith · 05-03-2010, 10:41 AM

Very good points by everyone & Phillip's...
Start at about 5% over the peak HP. & move up & down till it slows down is a good way. How the engine carries the hp & torque curve above peak can effect how far over you need to carry the RPM. If it drops like a rock after the peak you don't need to go there. If you have a dyno sheet study the curves around the peaks.
Once you find a nice single RPM for both shift points then work to find out if it wants low to second sooner and second to high streched out a little longer.
Some 3 speed combinations will run quicker with different shift points.
I wouldn't worry about what the other owner says. I would find out what it wants by testing. Then there is nothing left on the table orany unanswered questions. Besides... Thats the fun part of this sport! :~)

Henry S · 05-03-2010, 02:00 PM

I have heard of a theoritical way to determine correct shift point. You would need to know what the rpm's drop on each shift point, and have dyno sheets that go above peak horsepower. If the drop point on the 1-2 shift is 1000rpm then you can take the dyno sheets and average the horspower over a 1000 rpm spread and find the rpm number that gives the most horsepower average. For example:
5600-6600 = 425hp
5700-6700 = 430hp
5800-6800 = 435hp
5900-6900 = 410hp
then 6800 would be the best shift point. does anyone have experience using this method? I have not tried this or verified its results.

Adger Smith · 05-03-2010, 06:38 PM

That is great and what I was touching on by telling him to look at his dyno sheets and see what happens around the peaks. I have developed an excel program that works on stall speed and transmission gear ratios and shift points. It figures the RPM drop the % of drop and the difference between the stall speed and the shift drop, + or -...(I call it hang time) You still have to figure where your avg. best power is. It is very handy for changing gear ratios in the tranny and converters or picking the best ratio/converter combo. It would be nice to just spit out some numbers and be right, but testing is always what gives you the answer.

05-02-2010, 01:32 PM	#1
njk53 Senior Member Join Date: Jul 2007 Location: East China, MI Posts: 504 Likes: 0 Liked 0 Times in 0 Posts	Correct Shift Point I have talked to different people on this subject and received different answers. Maybe someone can help. For example: Your car has a big block Chevy engine and it makes a peak 450 lb/ft of torque at 3200 rpm and 440 HP at 5700 rpm. The car has a 350 turbo hydamatic. At what engine rpm should your 1-2 shift be? 2-3 shift be? __________________ Nelson Kowal Stock 345

05-02-2010, 02:04 PM	#2
Phillip marvetz Senior Member Join Date: Oct 2008 Location: Lynden ,WA Posts: 820 Likes: 0 Liked 3 Times in 3 Posts	Re: Correct Shift Point Depends on the converter stall. __________________ 2009 V/SA Record Holder

05-03-2010, 07:58 AM	#3
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: Correct Shift Point At the RPM that makes the quickest E.T. Pick some shift points and try testing your car instead of talking to people. If you listen the car will tell you what it likes. __________________ Adger Smith (Former SS)

05-03-2010, 08:41 AM	#4
njk53 Senior Member Join Date: Jul 2007 Location: East China, MI Posts: 504 Likes: 0 Liked 0 Times in 0 Posts	Re: Correct Shift Point Adger, where would you suggest as a starting point? The car is new to us and the previous owner never said where the shift points were. I have been having a hard time getting in touch with him. Car has a 4800 stall converter. __________________ Nelson Kowal Stock 345

05-03-2010, 09:58 AM	#5
buzzinhalfdozen Senior Member Join Date: Sep 2006 Location: Bellevue Ohio Posts: 984 Likes: 0 Liked 11 Times in 8 Posts	Re: Correct Shift Point Take Adgers advice, try a few different points. He's right the car will let you know what it wants, that plus the E.T. slip. Joe __________________ Joe Buchanan SS/BX 3117

05-03-2010, 10:18 AM	#6
Phillip marvetz Senior Member Join Date: Oct 2008 Location: Lynden ,WA Posts: 820 Likes: 0 Liked 3 Times in 3 Posts	Re: Correct Shift Point With that 4800 stall I would start shifting at 5800 then try a little higher each run until it slows down. Lot of guys are guilty of revving there engines to high, just because it will turn 7000 doesn't mean it is fast there. __________________ 2009 V/SA Record Holder

05-03-2010, 10:39 AM	#7
junior barns Senior Member Join Date: Jun 2006 Posts: 541 Likes: 11 Liked 20 Times in 14 Posts	Re: Correct Shift Point looking at yiour pk torque number, I think your converter stall may be to high?? I would start at 5500 on my shift and go from there with what you have. Last edited by junior barns; 05-03-2010 at 10:40 AM. Reason: spelling

05-03-2010, 10:41 AM	#8
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: Correct Shift Point Very good points by everyone & Phillip's... Start at about 5% over the peak HP. & move up & down till it slows down is a good way. How the engine carries the hp & torque curve above peak can effect how far over you need to carry the RPM. If it drops like a rock after the peak you don't need to go there. If you have a dyno sheet study the curves around the peaks. Once you find a nice single RPM for both shift points then work to find out if it wants low to second sooner and second to high streched out a little longer. Some 3 speed combinations will run quicker with different shift points. I wouldn't worry about what the other owner says. I would find out what it wants by testing. Then there is nothing left on the table orany unanswered questions. Besides... Thats the fun part of this sport! :~) __________________ Adger Smith (Former SS)

05-03-2010, 02:00 PM	#9
Henry S Junior Member Join Date: Aug 2007 Posts: 83 Likes: 11 Liked 19 Times in 7 Posts	Re: Correct Shift Point I have heard of a theoritical way to determine correct shift point. You would need to know what the rpm's drop on each shift point, and have dyno sheets that go above peak horsepower. If the drop point on the 1-2 shift is 1000rpm then you can take the dyno sheets and average the horspower over a 1000 rpm spread and find the rpm number that gives the most horsepower average. For example: 5600-6600 = 425hp 5700-6700 = 430hp 5800-6800 = 435hp 5900-6900 = 410hp then 6800 would be the best shift point. does anyone have experience using this method? I have not tried this or verified its results. Last edited by Henry S; 05-05-2010 at 10:10 AM.

05-03-2010, 06:38 PM	#10
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: Correct Shift Point That is great and what I was touching on by telling him to look at his dyno sheets and see what happens around the peaks. I have developed an excel program that works on stall speed and transmission gear ratios and shift points. It figures the RPM drop the % of drop and the difference between the stall speed and the shift drop, + or -...(I call it hang time) You still have to figure where your avg. best power is. It is very handy for changing gear ratios in the tranny and converters or picking the best ratio/converter combo. It would be nice to just spit out some numbers and be right, but testing is always what gives you the answer. __________________ Adger Smith (Former SS)