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.

Put a mech stop on the trans... 727 cop cars had the same thing so they couldnt leave them in low

Are you trying to lock it out of 1st gear, and use it as a 2 speed?

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.

Block the 2-3 shift valve in the 2nd gear position.

would you have a picture of this by chance ?
TIA as always !

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.

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.

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.

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?

If you decide to go the MVB route, make sure your shifter design will NOT allow you to go to reverse without some form of lockout.
As for special features of the VB, i would stay away from the rear band on in low for the same reasons as above.

Noted, good stuff