The GMC CCKW

I just replaced the master cylinder and I noticed it doesn't have the sensor that was on my old one. Which is correct sensor or no sensor?

If I have to add the sensor, will the old one work?

Neil

If it has a place to screw it in, yes it will work

I just checked the hole on the old one and it seems to be the same size as the plug on the new one. Now all I have to do is find the old sensor.

Neil

if you are talking about the stop light switch, you can rig up a more modern switch activation system, as detailed by another poster.

i did this, search for the thread if u are interested ( i just copied the instructions)

Indeed, I use a lever action switch whic is much better. The minute you touch the pedal, the brake light(s) come one

1957 Chev pick up switch. Jim Carter has them if you cannot find them locally. They are a pain to put in the 1st time. You really need 2 people

NAPA carries them

But you had better ask for a brake lite switch

John

Ok got it. I found the thread and that does make a good deal of sense. I will add that to the list.

You guys are a great resource.

Neil

Neil,

This summer I did the master in mine too. Moved the old brake light switch over but it did not work well.

As per our famous (or infamous) Dr. Deuce I replaced it with the mechanical switch. Found at the local parts store for $17. I had to remove the floor to mount it properly and some minor bending of the arm was involved.

Now the lights go on instantly upon touching the pedal.

This was another great safety upgrade.

Bill

One of the problems with the original is that it is a low pressure switch. Think about it. It is before the booster. There never is full pressure there. So if you replace the switch with a modern one made for the "other side" and hight pressure, the brake lights will never come on.

One note: You need to make sure you route the wires and secure them such that they don't get caught up in the pedals or linkages.

Another use for this switch:

If you are running 12 volts, you can use the stock 6 volt coil and an ignition resistor. I usually mount it under the dash on the passengers side. In the old days, the reason they used an external resistor coil was so that you could short out the resistor when starting to get a hotter spark. If you look at the battery voltage on a cold day when cranking, it drops down to below 10 volts.

That being said, you can also use this same switch on the passengers side of the toe board to "follow" the starter linkage so that when you step on the starter button, it will short out the ignition resistor and give you a hotter spark! The old CCKW will start like it is summer time at 20 below!

One other note. If you do 12 volts, you should move the vehicle feed (ammeter feed lead) directly back to the battery.