TH400 Kickdown Switch

[mclairmo]

I am running a Th400 with no kickdown switch. Is this ok? I cannot find any solid info on whether or not I really need it. Some say I need it or I will burn up the trans. Some say it is fine without it. Not racing the trans and not towing. It's used lightly. I know B&M and Lokar make kickdown switches but I am considering using a nitrous full throttle micro switch mounted to the carb to activate the kickdown switch at full throttle but don't want to go through the trouble if I don't really need to do this. Any insight?

[Sinister]

Not sure if it's necessary or not , but I'm running the Lokar switch. Makes flooring it a lot more fun.

[bigbadchev72]

I dont think that it is neccesary, you can manually do it with the shifter. I used a microswitch with a long lever i got out of johnstone supply for under $10 it is used in vending machines

[chevy_mike]

You don't need it but it also means it won't kick down a gear if you floor it. Last truck I had, the guy put a toggle switch on the dash so he could manually kick it down and let it hold that gear.

[turp mcspray]

You can find a factory switch that mounts on the gas pedal assembly, under the dash on any 3/4 or 1 ton truck through the 70s and 80s. These trucks are about as easy to find as a beer at a high school party! A new GM switch is under $30. I'd just snag a used one for next to nothing and grab the wiring harness at the same time.

[ChevLoRay]

My kickdown switch is not connected. When I had my valve body modified, the transmission shop guy, who is an old drag-racer, tested it to see if it was still working, and it was. So, until I install the drivetrain back into the truck, and use the Lokay stuff I have, it won't have one.

But, while I was still driving it, he put the smallest modulator he could get on it, a black one. This allowed the transmission to downshift based on vacuum and while not the same as a full-fledged kickdown, still made it more driveable.

[Longhorn Man]

i've heard tranny guys say it both ways.

[BossHogg69]

I didn't have one on my TH400 in the '69 and it was fine. of course, with a 454/3.73's, it had enough torque that it didn't matter much. If I really wanted to move around, I just pulled it in 2nd and laid the throttle down.

[ChevLoRay]

Originally Posted by Longhorn Man

i've heard tranny guys say it both ways.

[Longhorn Man]

after typing that, I wondered if anyone was going to say something.

[mikajo39]

Originally Posted by Longhorn Man

after typing that, I wondered if anyone was going to say something.

We sure are a mature group of fellows aren't we? haha

[ChevLoRay]

Everytime someone uses the word "tranny" I have to sit on my hands to keep from saying something. This time, I thought it was warranted...

[mikajo39]

Originally Posted by ChevLoRay

Everytime someone uses the word "tranny" I have to sit on my hands to keep from saying something. This time, I thought it was warranted...

It's ok... I actually do that same thing

[Lugnut64052]

Originally Posted by Longhorn Man

after typing that, I wondered if anyone was going to say something.

Actually, it'll run fine without the switch hooked up. You will get a 3-2 downshift, but you will never get a full-blown 3-1 downshift when you really tromp on it.

I *think* before about 1972, the downshift switch was mounted on the throttle linkage. It was a momentary contact switch activated by the carb lever. In '71 or '72, the switch got moved to the gas pedal.

[mclairmo]

I don't like the word "tranny". I use "trans". Is that any better, or it that actually worse?

[Longhorn Man]

that is correct. threy moved it to the throttle in 71 whey they went to a cable throttle instead of a throttle rod. The carb mounted switch can be quite hard to find... and harder to find working.

[70jnktrk]

The kickdown switch is not necessary on the TH 400..mine has been without since the swap...1991...tranny performs perfectly!...

[ChevLoRay]

I had a good 3-2 downshift and unless I was going really slow at no time would it drop into first. Never drove it with a proper electrical hookup to cause the downshift, but it has been checked and is operable. Like I said earlier, using the smalllest possible (physical size) modulator is one way to be able to live w/o the operable kickdown switch.

[turp mcspray]

Why not just add the switch? It's not like it's something expensive or difficult to do. Just curious.

[Longhorn Man]

if it is a 70 or older, it is expensive and difficult to make it work properly

[Sinister]

Originally Posted by Longhorn Man

if it is a 70 or older, it is expensive and difficult to make it work properly

'70 or older on the truck or transmission? On my '69 I just slapped on the Lokar switch ran it to 12 volts and had it working. Not sure how old the transmission is.

[mclairmo]

I think Longhorn Man was referring to an oem kickdown switch set up mounted on the intake and actuated by the throttle linkage. The Lokar switch mounts to the trans and will work with all Turbo 400s for all years.

[Sinister]

Doh, gotcha.

[turp mcspray]

He doesn't have to use the older style. The newer style is easy to find and cheap. It's not like it's a corvette or a mopar, where the "resto" police will get him because it's not original. LOL!

[mclairmo]

If I do add a kickdown switch, I'm going to use a nitrous full throttle micro switch and mount it to the carb. About $10-$15 and some wire. Cheapest way to do it that I could find other than a toggle switch on the dash.