1990 mecedes 190e2.6 l automatic not shifting into overdrive any ideas how to fix?

If your 1990 Mercedes 190E 2.6L automatic is not shifting into overdrive, it could be due to a few reasons. Check the Transmission Fluid level and condition, as low or dirty fluid can affect shifting. Additionally, inspect the throttle linkage for proper adjustment and ensure the kickdown switch is functioning correctly. If these aspects seem fine, it may be necessary to have the transmission diagnosed by a professional for internal issues.