400 kickdown

[53burb]

I have a recently rebuilt 400 tranny w/o the kickdown hooked up. When I bought the Burb, it wasn't installed, and I had the tranny rebuilt a few months ago. According to what I have read here, the tranny should still kickdown into 2nd gear w/o the kickdown installed & down into 1st with it installed.Well mine doesn't kick down into 2nd gear. Is there something wrong with the tranny that I need to have the shop look at??? It didn't
kick down before the rebuild either.

[GMan69]

Mine will kick down at slower speeds, such as turning a corner. One of these days, I might actually hook the darn thing up.

[JimKshortstep4x4]

The TH 400 should kick down under partial throttle, (slow speeds) without the detent switch hooked up. Two possible causes of your transmission not down shifting at slow speeds are: 1) modulator valve, 2) control valve. (Of course it is important that the vacuum line is hooked up to a good vacuum source on the engine).

I think that the modulator valve would be the most likely problem since you have had the transmission rebuilt. If you cannot get it to downshift after changing out the moulator valve, I would suggest taking it back to the rebuilders.

Jim

[53burb]

I am pretty sure the modulator was replaced during the rebuild, but I will definately look at it tomorrow. Is there a way to test it??? How exactly or at what throttle or RPM should the tranny kick down?? Where is the control valve?? The vacuuum is hooked up in the typical place, behind the carb on the intake manifold (full vacuum).

[Javy]

Hello,
The good thing about this 400 trans is that you don't need
a mechanical linkage for the the kick down.It is electronic.
I mounted a micro switch under my gas pedal to activate
"passing gear and NOS".Very simple.You don't need NOS for
your passing gear to work,just the switch.

[chevyguy_72]

Originally Posted by Javy

Hello,
The good thing about this 400 trans is that you don't need
a mechanical linkage for the the kick down.It is electronic.
I mounted a micro switch under my gas pedal to activate
"passing gear and NOS".Very simple.You don't need NOS for
your passing gear to work,just the switch.

Do you have any pics? maybe a write up?

[skokie]

You should be getting whats called a governor kickdown. Take it to the tranny shop, tell them whats going on and let them test drive it. Could be something as simple as a vac mod, bad governor or it could be something bad like the valve body. Keep us posted on what you find out..

[53burb]

I was talking with a friend about this problem. My truck will shift up and down fine when initially taking off or slowing down. It just won't kick down if you stomp on the gas if you just want to get on it or pass someone. I guess I do need the electric kickdown hooked up for this. I am going to feel real stupid if this is correct.

[69 longhorn]

Originally Posted by 53burb

I was talking with a friend about this problem. My truck will shift up and down fine when initially taking off or slowing down. It just won't kick down if you stomp on the gas if you just want to get on it or pass someone. I guess I do need the electric kickdown hooked up for this. I am going to feel real stupid if this is correct.

No, you dont need the elect kick down switch for the 3 to 2 kick down. The only function the elect provides is a 3 to 1 kick down (under 35mph). my bet is that you have a sticky valve in the control assy......I had a prob with mine , & it straightened up after some run time. You might run it by your trans builder tho..... crazyL

[53burb]

Not to drag this on, but if I step on it then it then it should kick down into 2nd if I am over 35mph, but if I have the electric kickdown hooked up, it would kickdown to 1st below 35??? Correct????

[69 longhorn]

Yup