* Shift Linkage: The linkage connects the shifter to the transmission. Worn or bent linkage components (rods, cables, or the shifter itself) can prevent the selector from properly engaging the 3rd, 4th, and 5th gear forks. Inspect the linkage for any obvious bends, breaks, or excessive play. A loose or improperly adjusted linkage is a common cause.
* Shift Fork(s): Inside the transmission, shift forks move to engage the gears. A bent or broken shift fork for 3rd, 4th, or 5th gear (or even a problem with the synchronizers on these gears) would prevent those gears from selecting. This is a more serious internal problem requiring transmission repair or replacement.
* Internal Transmission Damage: More severe internal damage, such as worn or damaged gears, bearings, or shafts, could also cause this issue. This might be due to a lack of lubrication, previous abuse, or age. This also necessitates a transmission repair or replacement.
* Clutch Issues (Less Likely but Possible): While less probable given you're getting into 1st and 2nd, a failing clutch could contribute to the problem by not fully disengaging, making gear selection difficult.
Troubleshooting Steps:
1. Visual Inspection of the Linkage: Start by carefully inspecting the entire shift linkage from the shifter to the transmission. Look for bent, broken, or loose components.
2. Check for Binding: Move the shifter gently. Does it feel stiff or sticky in any position? Binding could indicate a problem with the linkage or internal transmission.
3. Try Shifting With the Engine Off: With the engine off, try shifting into 3rd, 4th, and 5th gear. If it's easier to shift with the engine off, it could point toward clutch problems.
4. Listen for Noises: When trying to engage the higher gears, listen for any unusual noises emanating from the transmission. Grinding, whining, or clicking sounds usually indicate internal damage.
If you're not mechanically inclined: Take your Grand Am to a qualified mechanic specializing in manual transmissions. This is not something easily diagnosed and fixed without the appropriate tools and experience. Ignoring the problem could lead to further damage to your transmission. An accurate diagnosis will require a professional inspection.
