I run at 60 mph on the interstate, slowing down at bottom of exit car starts shuddering and dies.I getit restarted but Ihave to keep it in neutral to get home.I thought it may be a fluid ? but no. could it be blk.box/vac/or solenoid? confused.
This sounds like a case of the Torque Converter staying locked on when you come to a stop. There is a solenoid that commands the TC lockup. If this gets sticky you have the problem you describe. I think the TC lockup solenoid is under the side cover of this transmission.
Let us know what you find.
This is a common issue with these transmissions (the 125C). The lockup solenoid is easy to replace but the most trouble you are going to have is getting the side cover off. I would buy a genuine GM solenoid because they come with the plug and wiring attached to the solenoid. Aftermarket solenoids will have the wires on them but you will need to cut and splice wiring. Buy a solenoid, and a side cover gasket and 1 qt of ATF. Fluid loss during replacement will be minimal.
transman