One repair leads to another

2001 Chevy Express van recently had intake manifold replaced. Ever since then, shifts hard into and out of highest gear. Shifts great when engine is cold. No codes on computer. One tech suspects torque converter. Could this problem be related to manifold replacement?

A hard shifting tranny is sometimes caused by a faulty (worn) pressure solenoid in the tranny.

No relation to an IMG replacement.

If the solenoid is causing the hard shift, replace it ASAP before it damages the transmission and becomes more expensive.

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