What does the Trans Kick down solenoid do?

[erasedhammer]

The name is pretty straight forward, but what happens when its disconnected...?

I'm asking because I want to install an A2 engine harness before I have the 4l80 in.

The main difference between the A2 and A1/A0 harness is the trans kick down solenoid. So if it were disconnected would the 3l80 not function properly anymore?

 

[Wire Fox]

The name is pretty straight forward, but what happens when its disconnected...?

I'm asking because I want to install an A2 engine harness before I have the 4l80 in.

The main difference between the A2 and A1/A0 harness is the trans kick down solenoid. So if it were disconnected would the 3l80 not function properly anymore?

A kickdown switch is a switch that is trigged when you push the accelerator pedal to full throttle. In most cars, this would trigger the transmission to shift down to make use of that extra power you're producing. In the HMMWV< this also temporarily shuts off the cooling fan. Without checking the manual to be 100%, I'd have to presume that the kickdown solenoid is operating in the transmission in response to a signal from that switch to change transmission valving to force a downshift. I think that with it disconnected, you should still be able to use the transmission, but it won't have that full throttle downshift you would expect to have.

 

[erasedhammer]

A kickdown switch is a switch that is trigged when you push the accelerator pedal to full throttle. In most cars, this would trigger the transmission to shift down to make use of that extra power you're producing. In the HMMWV< this also temporarily shuts off the cooling fan. Without checking the manual to be 100%, I'd have to presume that the kickdown solenoid is operating in the transmission in response to a signal from that switch to change transmission valving to force a downshift. I think that with it disconnected, you should still be able to use the transmission, but it won't have that full throttle downshift you would expect to have.

Come to think of it, I think I've only ever had the transmission downshift once, and it didn't do much anyway. Most of the time I control the downshifting.

Never saw the need in a humvee since climbing a hill steep enough and at a slow enough speed (to allow a downshift) doesn't really help you climb the hill any better. I've been on the freeway at max throttle climbing up mountain passes but the transmission cant downshift anyway.

Other than that it looks like installing the a2 can be done at any time and still have the truck run.

 

[Retiredwarhorses]

TH400 is mechanical, it does not use a kick down switch...the switch tells the fan to disengage if it's on for passing or more power. The trans kicks down via the mechanical modulator.

 

[erasedhammer]

TH400 is mechanical, it does not use a kick down switch...the switch tells the fan to disengage if it's on for passing or more power. The trans kicks down via the mechanical modulator.

Another one of am generals mislabeled harness's?

I have my fan timer disconnected so my fan is on all the time. Does this affect how the kick down solenoid works?

 

[erasedhammer]

TH400 is mechanical, it does not use a kick down switch...the switch tells the fan to disengage if it's on for passing or more power. The trans kicks down via the mechanical modulator.

Why then is there a wire coming from the engine harness to the transmission.
There's a tab connector on the side of the 3l80 which connected up to the engine harness...

 

[Retiredwarhorses]

Here is what I know..I'm no trans guy. You can disconnect the cable on the modulator at the pump, when you driving, pull the cable, the trans will drop down a gear, my schematic is for a 4L80E.

 

[erasedhammer]

Here is what I know..I'm no trans guy. You can disconnect the cable on the modulator at the pump, when you driving, pull the cable, the trans will drop down a gear, my schematic is for a 4L80E.

Well I've been driving with the wire disconnected from my 3l80 and haven't noticed anything different.

 

[pjwest03]

The THM400 and 3L80 have a kickdown solenoid in the valve body. The harness wire comes from the kickdown switch on the injection pump (circuit 315) and provides power to solenoid around 3/4 throttle. This should not be confused with the fan control also on the pump. THM400's may have a second tab on the case if equipped with a lockup torque converter.

 

[erasedhammer]

The THM400 and 3L80 have a kickdown solenoid in the valve body. The harness wire comes from the kickdown switch on the injection pump (circuit 315) and provides power to solenoid around 3/4 throttle. This should not be confused with the fan control also on the pump. THM400's may have a second tab on the case if equipped with a lockup torque converter.

So if theres a second connector where would it lead to? The injection pump?
I thought all 3l80s had lock up torque converters? And the TH400s were the ones with the lock up feature? I'll have to see if theres a second tab on mine.

 

[pjwest03]

So if theres a second connector where would it lead to? The injection pump?
I thought all 3l80s had lock up torque converters? And the TH400s were the ones with the lock up feature? I'll have to see if theres a second tab on mine.

Sorry, my bad, the second tab is for variable pitch converters. Too many variations on these things. My mind got crossed with electrically controlled lockup converters.

 

[Wire Fox]

Oh good, you guys found the same bits of information that I did and was just about to report in. According to bangshift.com, the THM400 has two kickdown mechanisms: vacuum based and solenoid based. The vacuum system is for kickdown at speeds below 30 MPH. Anything over requires the actuation of the kickdown solenoid. The actual line of what speed it does that is probably a lot different for our HMMWVs...

http://bangshift.com/general-news/b...-kickdown-switch-in-a-turbo-400-transmission/

 

[erasedhammer]

Sorry, my bad, the second tab is for variable pitch converters. Too many variations on these things. My mind got crossed with electrically controlled lockup converters.

But aren't 3l80s supposed to have locking torque converters? I don't see how the clutch would be controlled, but I've heard they have them.

 

[pjwest03]

But aren't 3l80s supposed to have locking torque converters? I don't see how the clutch would be controlled, but I've heard they have them.

As far as I can find, it's a stock GM6 (6 bolt) heavy duty converter with a 1350 stall and no lock up.

 

[Retiredwarhorses]

Injector pump has cold start advance and fuel solenoid. The fan cutoff switch is attached on a bracket and comes in contact when it's WOT to cut the fan off when passing. There is no kick down solenoid on the pump...

 

[pjwest03]

Injector pump has cold start advance and fuel solenoid. The fan cutoff switch is attached on a bracket and comes in contact when it's WOT to cut the fan off when passing. There is no kick down solenoid on the pump...

The kickdown switch is activated on the pump. The solenoid is in the valve body of the transmission. THM400's have been equipped with the solenoid from the very beginning in 1964.

 

[Retiredwarhorses]

The kickdown switch is activated on the pump. The solenoid is in the valve body of the transmission. THM400's have been equipped with the solenoid from the very beginning in 1964.

that switch is also called a fan cutoff switch,that's all I have ever known it to be called and it's in the TM as such.
it looks like in a TH400 application they call it kick down switch, in a 4L80E application it's called a fan cutoff switch.

 

[pjwest03]

that switch is also called a fan cutoff switch,that's all I have ever known it to be called and it's in the TM as such.
it looks like in a TH400 application they call it kick down switch, in a 4L80E application it's called a fan cutoff switch.

For TH400's the solenoid replaced the mechanical rod linkage on other units. And, I suspect that there wasn't room for the rods in the original cars that were fitted with a TH400. They were moving to bigger power and just plain bigger in the land yachts at the time (1964 Cadillac and Buick) and needed a trans that could take it.

 

[Bulldogger]

My trans does not kick down properly, hasn't since delivery. I've checked the circuit of the exterior switch on the throttle arm, and it works fine. That switch just makes and breaks connection.

Apparently I need to replace the kickdown solenoid itself. Joy, joy, it's internal and I have to drop the pan (which I did two years ago for a flush and filter already).

Does anyone know if I have to use the AMG part 5945-01-175-7318 or will any 3L80 TH400 kickdown switch do the trick? Obviously, prices differ. Appearance is the same, but I worry that one is a 24V version and putting a civilian 12V version will be unhappy.

I notice that this NSN is listed on several sites for sale for H1's, and unless I am mistaken H1's were 12V or could be...

So can I use any AC Delco 3L80/TH400 solenoid?

Bulldogger

 

[Milcommoguy]

Kick down or cable pull.

Kick down / fan switch side of IP. Does two things.

Cable pull modulator side of trans to the IP throttle sets the shift points.

Simple as pie or pi, CAMO