There are several bulletins from GM pertaining to shifting quality and problems. In order to accurately diagnose this problem you should take the car to a reputable transmission shop for a thorough diag. Most will give a free estimate and always ask for an estimate and inquire about parts and labor warranties/guarantees.
#03-07-30-012B: Transaxle or Transmission Slips, Wont Shift, No Reverse, 2nd, 3rd or Overdrive, Erratic Shifts (Replace Driven Sprocket Support Assembly) - (Aug 22, 2005)
This bulletin is being revised to update model years, clarify part inspection procedure and warranty return request. Please discard Corporate Bulletin Number 03-07-30-012A (Section 07 -- Transmission/Transaxle).
Some customers may comment that the transaxle/transmission slips, will not shift, will not backup/no reverse, no 2nd, 3rd or overdrive gears and erratic shifts.
A sleeve WITHIN the driven sprocket assembly (401) may have shifted due to insufficient interference fit, blocking the oil feed hole for the second clutch.
Callout "A" shows oil feed holes that are not blocked. Callout "B" shows what the oil feed holes will look like if the sleeve has shifted.
Important: Inspections of returned Driven Sprocket Support Assembly at the Warranty Parts Center (WPC) indicated that the Driven Sprocket Support Assemblies are being replaced unnecessarily. Technicians should carefully inspect the sleeve inside the Driven Sprocket Support Assembly for the correct position before replacement.
Driven Sprocket Support Assembly
#02-07-30-013E: Incorrect Transmission Shifts, Poor Engine Performance, Harsh 1-2 Upshifts, Slips 1st and Reverse, Torque Converter Clutch (TCC) Stuck Off/On, DTCs P0757, P0741, P0742, P0730, P0756 - (May 20, 2005)
This bulletin is being revised to include additional diagnostic information and clarify model usage. Please discard Corporate Bulletin Number 02-07-30-013D (Section 07 -- Transmission/Transaxle).
Some owners may comment on any one or more of the following conditions:
The most likely cause of the various conditions may be chips or debris:
Important: It has been found that in most cases that the scratches are not severe enough to catch your fingernail.
Important: Clean the valve body with the machined side down so debris may escape.