Changing Shift Points

knutson · #1 (**permalink**) 08-17-2004, 01:45 PM

does anybody know if you can change the shift points of the a340e. ie,through the ecu...i have an 04 tundra and i like the way it shifts from 1-2,2-3 when it's cold...it's real fast (low rpm change) and smooth. then of course when it warms up it's back to normal..(harder shifts and higher rpm levels).

RockyMtnRay · #2 (**permalink**) 08-17-2004, 02:06 PM

Quote:

Originally Posted by knutson

does anybody know if you can change the shift points of the a340e. ie,through the ecu...i have an 04 tundra and i like the way it shifts from 1-2,2-3 when it's cold...it's real fast (low rpm change) and smooth. then of course when it warms up it's back to normal..(harder shifts and higher rpm levels).

Possibly. One member has claimed that Jet Performance has cracked Toyota's proprietary programming code for the ECU...and could therefore theoretically reprogram the transmssion shifting. Many other members have expressed a lot of doubt about whether Jet actually has cracked the ECU code, and if they have, how good a job they're doing of reprogramming the ECU. If you go this route, you'll be a pioneer venturing into basically unknown territory. Let us know if you do and how well it works out for you.

The reason the ECU shifts as it does is to minimize emissions when the engine is cold.

DevinSixtySeven · #3 (**permalink**) 08-17-2004, 02:20 PM

the shift parameters (rpm and vacuum) are posted in the garage, might make a good starting point.

knutson · #4 (**permalink**) 08-17-2004, 04:53 PM

Quote:

Originally Posted by DevinSixtySeven

the shift parameters (rpm and vacuum) are posted in the garage, might make a good starting point.

not sure what u mean by this...please advise...

Dude Boy · #5 (**permalink**) 08-18-2004, 08:52 PM

I've read on TS that the change in shift points is controlled by a temperature sensor. The temperature sensor can possibly be "tricked" by inserting a resistor in the circuit. If that works, some of the downside might be continued "open loop" operation (with poor mileage) and increased wear on the tranny due to the soft shifts. If you get really good with your right foot, you can pretty much tailor the shifts yourself.

knutson · #6 (**permalink**) 08-19-2004, 03:23 PM

Quote:

Originally Posted by Dude Boy

I've read on TS that the change in shift points is controlled by a temperature sensor. The temperature sensor can possibly be "tricked" by inserting a resistor in the circuit. If that works, some of the downside might be continued "open loop" operation (with poor mileage) and increased wear on the tranny due to the soft shifts. If you get really good with your right foot, you can pretty much tailor the shifts yourself.

i believe u r absolutely correct in that it is controlled by a temp sensor,only when the tranny is "cold" does it shift smooth and at a very low rpm range-it's like 1-2 2-3 r right behind each other.what would happen if i disconnect(can you even) or elimanate the sensor alltogether.or is that a no-no..

Dude Boy · #7 (**permalink**) 08-20-2004, 01:18 AM

My understanding is that the soft shifts are the result of the computer reducing the line pressure in the transmission. If you ran it that way all the time, the life of the clutch packs would be shortened. I think it's best for the tranny to just get used to it and live with it. If you search for posts by Mudog715 containing the word transmission, you should find some info on how the transmission is controlled. He has modified his truck to give softer shifts while in 4WD LO, by disconnecting the sensor that determines when low range is selected. You might even be able to email him or send a PM, but I don't believe he has been active on TS for a year or so.