Stall when braking
 

Hello, All! Please help, as I am at my wits end, and I know there are some smart folks out there. 1987 IROC-Z, 5.7 TPI, 700R4. (this is an engine swap...) Intermittent stalling while braking and turning(mostly downhill). Converter seems to be erratically locking/unlocking while braking as noted by voltmeter/ tach gage. Should my 4th Clutch switch be N.O. or N.C.? as mine is N.O. and book states "closed until 4th gear...". I have replaced TCC solenoid, and it did help with stalling, but still getting erratic locking while braking. Brake switch/ wiring good. Cut tan/black wire at ECM and drove around with VOM on computer and manual switch to ground. Trans seemed fine when I would manually ground while braking/ but computer operation was strange. I was getting 0 volts up until around 40 mph, then 13.8 volts above 40 mph, seemed to be consistent in operation. I am kind of stuck at this point and I feel that someone may have also experienced this and could provide some insight. I really appreciate your time in reading this and responding! Cheers!

Re: Stall when braking
 

Braking draws vacuum in a power-brake system.

You are having transmission problems when braking.

My shallow understanding of the 700R4 tells me there is a vacuum switch that sends commands to the transmission.

Bad switch, or bad wiring of the switch. Bad ground on the transmission vacuum switch?

Re: Stall when braking
 

No, no vacuum switch. It is either ECM or something in trans, and I am leaning toward trans. Three wire plug, purple =12v from brake switch, dark green= ECM 4th gear and tan/black= ECM ground.