Technical > Dan Dishon's Transmission Den

converter fallback

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spookie:
Running sbc with PG. Shift at 6200 fallback is 5200.Runs 5.60s@117mph 1/8mi. Using Valvoline synthetic dextron VI. is this to much fallback?

bikeguy307:
Depending on weight it could be. 1000rpm is a base line number, but a lighter cars seem to like less fall back (looser converter). My car is 2080 with driver 5800 stall shift at 7000. The fall back is around 900.

JrFuel Hayden:
Shifting at 7000, and stall at 5800, isn't that a 1200 fall back ? It could be your converter maker is not right about your true stall.
My RacePak shows my converter flashes right after the shift to 8500 rpm after a 9700 shift. All the converter people I talk to say the RPM  right after the shift is the TRUE stall.
If you shift at 7000, and your fall back is 900, that would mean your true stall is 6100 rpm, Right ?

Just my 2 cents,
Jon

bikeguy307:
Depends on who you talk to, as to what is true stall. Some say it is the fallback number, some say it the number from a stall check (This is the number I use). Around 300rpm difference is normal between a stall check number and a fall back number.

JrFuel Hayden:
That's why I always ask where their lowest RPM goes to after the shift, Great if they have a Data computer , if not a play-back tac, or a camera aimed at the tac, and reply it.
Just trying to keep things consistant. How is a "stall check" is done ?
I have seen many a happy racer once they change converter , trans gear and or rear gears to better match engine power range.
Cheers

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