H Pattern Gear Selector on an Automat - Lexus IS Forum
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post #1 of 6 (permalink) Old 05-31-2019, 06:09 PM Thread Starter
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H Pattern Gear Selector on an Automat

I have this concept that i want to try but i don't know how i would accomplish it or even if it is possible. Ive tried to research on it and i couldn't really find anything like it. Basically what i was thinking is the IS300 auto transmission already has a 1st 2nd, and 3rd gear selection option. My idea is to take those and put them in an H shifter pattern and somehow add a 4th and 5th gear selection option with the reverse as well and maybe a switch or something for park. Would this be possible at all through programing and electrical work or not?
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post #2 of 6 (permalink) Old 05-31-2019, 06:42 PM
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I'm unfamiliar with the automatic in these cars, but because they have the up/down shift buttons on the steering wheel, I would assume the actual shift lever is nothing more than a multi-position switch - and NOT a physical linkage to the valve body.

If so, you could reverse engineer what signals the original gear lever is putting out in its various positions, fabricate or modify an existing H pattern shifter gate, and outfit it with microswitches in each gate. Then you could program a microcontroller to send the appropriate gear-position signals to the ecu.

Sounds like a lot of work...
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post #3 of 6 (permalink) Old 05-31-2019, 09:35 PM Thread Starter
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Originally Posted by Hodgdon Extreme View Post
I'm unfamiliar with the automatic in these cars, but because they have the up/down shift buttons on the steering wheel, I would assume the actual shift lever is nothing more than a multi-position switch - and NOT a physical linkage to the valve body.

If so, you could reverse engineer what signals the original gear lever is putting out in its various positions, fabricate or modify an existing H pattern shifter gate, and outfit it with microswitches in each gate. Then you could program a microcontroller to send the appropriate gear-position signals to the ecu.

Sounds like a lot of work...
I would be able to add a 4th and 5th gear selection as well? It sounds like the ECU is responsible for changing gears.
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post #4 of 6 (permalink) Old 05-31-2019, 10:43 PM
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Quote:
Originally Posted by Hodgdon Extreme View Post
I'm unfamiliar with the automatic in these cars, but because they have the up/down shift buttons on the steering wheel, I would assume the actual shift lever is nothing more than a multi-position switch - and NOT a physical linkage to the valve body.

If so, you could reverse engineer what signals the original gear lever is putting out in its various positions, fabricate or modify an existing H pattern shifter gate, and outfit it with microswitches in each gate. Then you could program a microcontroller to send the appropriate gear-position signals to the ecu.

Sounds like a lot of work...
Unfortunately it does have a physical cable link to the trans, but i am pretty sure this is mostly to shift it between P-R-N-D. It may also trigger the 1-2-3-M shift, not 100% sure. If you read through the posts on here some have mucked up the lever setting when modding their solenoids and cant get it to shift into D or R.

You may be able to link an H into the e-shift to try and simulate it, but you wont get first and the shifts will still feel sluggish like an auto, and if you leave the shifter in a high gear it will probably automatically shift into a lower gear when starting off leaving it feeling at odds will it gets back up to that gear. Alternatively you can try and jimmy up a connection to the solenoids or ECU, not sure how hard that would be though.

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post #5 of 6 (permalink) Old 06-01-2019, 06:11 AM
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You would need like a Dictator to control the transmission. Then take a stick in a swivel ball mount. Put the different triggers switches in a box for the stick to press.


But it seems a waste of energy to me. But that should point you in a direction.

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post #6 of 6 (permalink) Old 06-01-2019, 06:02 PM
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I'm unfamiliar with the automatic in these cars, but because they have the up/down shift buttons on the steering wheel, I would assume the actual shift lever is nothing more than a multi-position switch - and NOT a physical linkage to the valve body.
There's both a physical link inside to the valve body and a selector switch on the right side of the transmission. You can actually shift these transmissions by hand if the ECU to transmission cable gets cuts. It's some redundancy Lexus built into these cars (along with the MX bus which will keep working even if it's cut because it's a ring).

You could implement this H pattern by creating a dummy shifter box with the H pattern and 7 switches to show which gear is currently selected, then you could tap into the shifter wiring to tell the ECU what "gear" you've selected bypassing the switch on the side of the transmission. You'd probably need a "neutral" switch too and a reverse switch for sure.

It would take making a prototype and seeing how it reacts. I'm thinking something like a raspberry pi between the switches and the ECU in order to program in some sanity checking. The ECU itself won't let you shift from say 5th to first even if you select them.

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But it seems a waste of energy to me. But that should point you in a direction.
Agreed. It's an interesting thought experiment. Might even be worth prototyping it for fun but pointless in the long run because nothing can override the shifting logic built into the ECU.
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