Olds Silhouette Transmission shifting

jmac28

I have a 2000 Olds Silhouette with 160000. After my van gets to temp the transmission suddenly erratically shifts, as though it does not know what gear to shift into. The tachometer jumps quickly from 500rpm to 3500rpm while the van bucks to try and find a gear. Battery light illuminates when power surges and is currently impossible to drive anywhere. I have attempted to diagnose by researching some possibilities. The Transmission seems to shift into second gear w no problem but fourth gear and overdrive is what triggers the erratic shifting. Motor runs great so I'm thinking its electronic. Pressure control solenoid? Shift solenoids? Are the Shift Solenoids accessible form the tran pan? Where is the PCS located? How about the vacuum modulator? I really don't know where to start. i certainly appreciate any help.
Finally, is there wheel speed sensors that may talk to the TCM? I had my tires changed the day before this started. Thought it mite have a relationship with shifting seems all four tires were removed and replaced. Thank you in advance

mitzij

Sounds like you need a professional. Find a reliable transmission shop and have them check it out. Wheel speed sensors can aggravate the ABS and traction control systems (will activate the ABS light), but it sounds like you have transmission trouble. Good Luck!