Kickdown going back to third too soon

[Ron]

Maybe this will help...

Basically, shifting is done using two solenoids (to open and close two valves). They are controlled by the "computer governor" (GC), which receives input from a signal generator (for output shaft RPM input), a multifunction switch (for operator selected gear input), a "governor cable" (for operator selected acceleration level input), a micro switch (for operator selected downshift request input).
Let's go for a ride...
When you are sitting in gear, both solenoids are ON (1st gear).
Floor it!...
As you continue to accelerate, the generator outputs more voltage. The GC sees the rise in voltage and turns off solenoid A (now 2nd gear). The load on the engine raises so the RPMs and the generator's output voltage drop back down. Continuing to accelerate, the GC sees another rise in RPMs and turns off solenoid B (now 3rd gear).
Cruising...
The generator's input is combined with the governor cable's input to determine the point to turn a solenoid on/off (engine load versus demand).
Passing...
Putting the pedal to the floor closes the kickdown microswitch (request for it to override the GC). The GC will turn a solenoid ON (B then A), iff it is safe to do so.

If you haven't, check out:
https://dmctalk.org/showthread.php?3...ssion-Governor
R4141EC.jpg

[jangell]

Thanks -- that does help.

That governor thread is extremely valuable -- I've gone over it a number of times in the past. I think my confusion comes from this part of the description about how the kick-down works:

"It basically provides a path to ground for the solenoids, bypassing the voltage comparing Op-Amp part of the circuit, and forcing the car into a lower gear. Once you let up off the gas, the kick down opens up, and the solenoids are once again controlled by the comparator Op-Amps."

That suggested to me that the comparators (and thus the generator and throttle position) weren't considered when the kick-down is engaged, but that's clearly not true.

Really, it's just that I suck at reading logic flow in circuit diagrams.

-- Joe

[Ron]

I think you may be missing that the solenoids are wired hot (12V) at all times. (They are ground controlled -- Pull the fuse and it is in 3rd!)
...The GC grounds a solenoid to turn it on, forcing a LOWER gear. The microswitch's input (ground) is fed into the GC circuit's where it will make the GC ground a solenoid. It's signal is on the Green wire that taps between D2 and D3 in the schematic.

[jangell]

Ah, you're right! I play with microcontrollers enough to know that it's easier to switch ground with a MOSFET than 12v (I know this isn't quite the same, but still, I'm still used to switching ground). It's even mentioned in that thread -- I should have re-read it more thoroughly last time. That explains it. Thanks!

-- Joe

[Ron]

YW!

[David T]

Maybe this will help...

Basically, shifting is done using two solenoids (to open and close two valves). They are controlled by the "computer governor" (GC), which receives input from a signal generator (for output shaft RPM input), a multifunction switch (for operator selected gear input), a "governor cable" (for operator selected acceleration level input), a micro switch (for operator selected downshift request input).
Let's go for a ride...
When you are sitting in gear, both solenoids are ON (1st gear).
Floor it!...
As you continue to accelerate, the generator outputs more voltage. The GC sees the rise in voltage and turns off solenoid A (now 2nd gear). The load on the engine raises so the RPMs and the generator's output voltage drop back down. Continuing to accelerate, the GC sees another rise in RPMs and turns off solenoid B (now 3rd gear).
Cruising...
The generator's input is combined with the governor cable's input to determine the point to turn a solenoid on/off (engine load versus demand).
Passing...
Putting the pedal to the floor closes the kickdown microswitch (request for it to override the GC). The GC will turn a solenoid ON (B then A), iff it is safe to do so.

If you haven't, check out:
https://dmctalk.org/showthread.php?3...ssion-Governor
R4141EC.jpg

While this explanation is mostly correct it is not that simple. The valve body also controls the shifts too. For instance it will not allow upshifts or downshifts unless you are within the correct RPM range for the shift. The solenoids do tell the valve body what gear to be in but the valve body has the final control. If the shift hold is working the shift computer can command the transmission to go into 3rd but the shift lever can limit your upshifts to 2nd or 1st. Anyway if you are not shifting correctly, chances are the shift computer (GC) is not functioning correctly. Most of the time it is the shift computer but before you say that, you have to inspect the wiring harness. If it has not been secured properly away from the exhaust pipes it gets melted and can cause all kinds of weird problems. You also should go over every external adjustment too. Unlike most cars the throttle cable does not activate the kick-down. The micro switch on the throttle spool does that. That is why there are 2 switches there at WOT (Wide Open Throttle) on automatics. 1 for the kick-down and the other to force the Lamda system to full duty cycle for more fuel.