Shifting problem
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Shifting problem OK, As suggested by another member I'll post this question here.
I have a friend with a 55 Chevy Bel Air which has a LS1 engine with a 4L60E transmission, the problem is that if he floors it it will not change up but if he drive sedately it changes fine, the kick-down seems to work fine, but I have also noticed the Rev counter does not always work and my thought is that the TCU is not receiving the correct signal from the ECU because it does not know the engine speed and therefore it doesn't know to change up, HOWEVER I am no expert and would appreciate input from anyone who knows how these things are meant to work.
HELP
Gary
I have a friend with a 55 Chevy Bel Air which has a LS1 engine with a 4L60E transmission, the problem is that if he floors it it will not change up but if he drive sedately it changes fine, the kick-down seems to work fine, but I have also noticed the Rev counter does not always work and my thought is that the TCU is not receiving the correct signal from the ECU because it does not know the engine speed and therefore it doesn't know to change up, HOWEVER I am no expert and would appreciate input from anyone who knows how these things are meant to work.
HELP
Gary
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Joined: Oct 2014
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From: Virginia
WOT shifts are controlled by 3 things:
1. TPS - this signal determines if the throttle is considered WOT or not.
2. VSS - vehicle speed sensor, speed to shift
3. RPM - you already said you had issues with this
The PCM shifts at WOT using speed and RPM. Once BOTH are met, it will shift. Many set the speed low, and use RPM as the trigger. It's easier to stay in your torque band doing this instead of using speed.
His engine would probably have a lot more problems if you are seeing a bad rpm signal. That's coming from your crank position sensor.
Are you seeing these errors in the scanner or on the gauge?
1. TPS - this signal determines if the throttle is considered WOT or not.
2. VSS - vehicle speed sensor, speed to shift
3. RPM - you already said you had issues with this
The PCM shifts at WOT using speed and RPM. Once BOTH are met, it will shift. Many set the speed low, and use RPM as the trigger. It's easier to stay in your torque band doing this instead of using speed.
His engine would probably have a lot more problems if you are seeing a bad rpm signal. That's coming from your crank position sensor.
Are you seeing these errors in the scanner or on the gauge?
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Joined: Oct 2014
Posts: 1,220
Likes: 179
From: Virginia
