1996 Chevrolet Lumina APV. Engine Size : 3400 Question : My van lost all gears fwd and reverse without any signs or symptoms.. But if my transaxle is cold I can go about 5 minutes until I start having problems again. After the engine warms up.

I am thinking it is the vacuum modulator? Please let me know if there is any other possibilities that could have this effect or cause if these symptoms.

Answer: There is a vacuum modulator. It is located on the front of the transmission. Stand in front of the van and look down between the radiator and the trans. It sticks out of the trans with a vacuum hose on pipe that runs to the engine. But is would say this is not going to be your shifting problems. If it were bad, or has no vacuum to it, it would just shift very late and hard. Temperature or time of running would not be a factor. It does not effect reverse gear either. Sounds like it is time for a rebuild or replacement.

Lumina ABS sensor Locations

1999 Chev Lumina sedan.
Question: the ABS light comes on and stays on - if it is the sensor - where are they and how do I change ?

Answer: It could be a sensor. Wheel speed sensors are located within the wheel bearing hub of each wheel. You would need to scan the ABS computer for codes to be sure. Speed sensors / hubs are expensive and guessing is not really an option.