M1151A1 stalls when braking in park

[Minskey]

I'm working on restoring my m1151a1 and it seems to function flawlessly other than when I start it and push the brake to move it into drive, it will bog the engine down bad enough to stall it out. I did verify that it's idling at the correct 700 rpm.

 

[Mogman]

Welcome to the SS forums, you will find allot of people here to help.
The first thing I would do is unplug the molded plug connected to the brake light switch, there are two circuits there, one is two individual wires and the other is two wires through a molded plug.
If that stops the issue then ether there is a wiring error or you could have a defective TCM.
What apparently is happening is the torque converter is trying to lock when you step on the brake, this can be confirmed by starting the truck in neutral and then step on the brake, if the torque converter tries to lock it will not pull the engine down.

 

[Minskey]

Welcome to the SS forums, you will find allot of people here to help.
The first thing I would do is unplug the molded plug connected to the brake light switch, there are two circuits there, one is two individual wires and the other is two wires through a molded plug.
If that stops the issue then ether there is a wiring error or you could have a defective TCM.
What apparently is happening is the torque converter is trying to lock when you step on the brake, this can be confirmed by starting the truck in neutral and then step on the brake, if the torque converter tries to lock it will not pull the engine down.

Awesome! I'll try this this weekend and get back to you. Nothing would surprise me as I found MANY wires either incorrectly installed, or indiscriminately severed during demil

 

[Mogman]

UPDATE?

 

[Minskey]

UPDATE?

I am still working on testing this - when warm it only appears to do it when coming to a stop after driving at considerable speed, and even then only sporadically. I did unplug the molded brake switch plug as you said but I'm not sure if it stopped because of that or because it was warmer. I did change the power steering filter and that didn't solve the issue. I also verified the generator can be spun by hand when the vehicle is turned off as a g503 member suggested.

 

[Mogman]

So it just stopped pulling the engine down when in park all by itself?