28/03/2026
A 6L45 transmission that has lost 1st gear and bangs back to first gear may have a problem with worn check balls in the valve body.
In this instance, the customer reported intermittent banging back to first gear followed by loss of 1st gear.
The solution involved removing and disassembling the valve body, cleaning and refitting it with updated check balls, replacing the filter and oil, and performing a transmission relearn procedure.