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904 how to stay in 2nd
#2904747
03/31/21 09:28 PM
03/31/21 09:28 PM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
OP
Circle Track
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OP
Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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I have a stock 904 (regular rebuild). I need a much lower overall ratio (in the 5's). Can I change it to where it stays in 2nd? I'll be in 2nd when the green flag drops & I want it to say there (& to last). What mod(s) should I do? thank you for your time.
live every 24 hour block of time like it's your last day on earth
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Re: 904 how to stay in 2nd
[Re: A990]
#2904851
04/01/21 09:49 AM
04/01/21 09:49 AM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
OP
Circle Track
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OP
Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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thank you . I want it to shift from 1st to 2nd normally then stay in 2nd for the rest of the race. I want no upshift to 3rd.
live every 24 hour block of time like it's your last day on earth
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Re: 904 how to stay in 2nd
[Re: A727Tflite]
#2904956
04/01/21 03:27 PM
04/01/21 03:27 PM
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Joined: Jan 2003
Posts: 25,786 Rio Linda, CA
John_Kunkel
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Joined: Jan 2003
Posts: 25,786
Rio Linda, CA
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Block the 2-3 shift valve in the 2nd gear position. Isn't there the possibility it will downshift to 1st at WOT? I'm thinking a full manual VB is the only sure way.
The INTERNET, the MISinformation superhighway
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Re: 904 how to stay in 2nd
[Re: John_Kunkel]
#2904964
04/01/21 03:56 PM
04/01/21 03:56 PM
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Joined: Mar 2011
Posts: 3,075 Michigan
A727Tflite
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master
Joined: Mar 2011
Posts: 3,075
Michigan
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Block the 2-3 shift valve in the 2nd gear position. Isn't there the possibility it will downshift to 1st at WOT? I'm thinking a full manual VB is the only sure way. I agree on the use of a full manual. Much simpler. I can’t get to my schematics right now so I can’t answer your question. I would think a blocked gov plug would prevent that but not positive.
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Re: 904 how to stay in 2nd
[Re: A727Tflite]
#2905001
04/01/21 05:01 PM
04/01/21 05:01 PM
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Joined: Jan 2003
Posts: 25,786 Rio Linda, CA
John_Kunkel
Too Many Posts
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Too Many Posts
Joined: Jan 2003
Posts: 25,786
Rio Linda, CA
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A 1-2 shift valve blocked in the open position and a 2-3 shift valve blocked in the closed position would, theoretically, engage only second gear with the shifter in D, 2 or 1. Block the 1-2 in the direction of the white arrow and the 2-3 in the direction of the red arrow.
The INTERNET, the MISinformation superhighway
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Re: 904 how to stay in 2nd
[Re: John_Kunkel]
#2905006
04/01/21 05:06 PM
04/01/21 05:06 PM
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Joined: Mar 2011
Posts: 3,075 Michigan
A727Tflite
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master
Joined: Mar 2011
Posts: 3,075
Michigan
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Just looked at the schematics.
It appears to me blocking the 2-3 in the second gear position should accomplish the feat.
At least that’s what I am taking away by looking at these valve positions in both kickdown at speed, drive 2nd, etc.
I think the key is the position of the governor plug in these positions. I’m thinking the TP will accomplish the auto 1-2 but cannot force a 3-2 since the 2-3 is blocked in 2nd gear.
So for the op - you can experiment or just use the manual shift valve body or place the shifter in second gear and leave it there. I don’t think you can force a 2-1 at WOT unless the gov pressure is very low (on the track). But I never tried it. If you can, then use a diesel governor - if you have a late model 727.
Last edited by Transman; 04/01/21 06:01 PM.
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Re: 904 how to stay in 2nd
[Re: A727Tflite]
#2905232
04/02/21 08:52 AM
04/02/21 08:52 AM
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Joined: Nov 2003
Posts: 36,040 Lincoln Nebraska
RapidRobert
OP
Circle Track
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OP
Circle Track
Joined: Nov 2003
Posts: 36,040
Lincoln Nebraska
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awesome tech much appreciated . I think I will block it & see how it acts. & actually as low ratio as I will have I think I could start in 2nd & stay there. thank guys! EDIT If I end up haveing to go to a manual VB is there one you would recommend & any special features that I need in that VB when I make my selection?
Last edited by RapidRobert; 04/02/21 09:00 AM.
live every 24 hour block of time like it's your last day on earth
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