Transmission shifting fast into overdrive

[Job1972]

I ran over a 18 wheeler tire , it knocked my exhaust a loose & a few days later my
transmission started shifting into overdrive at 30 mph. Can anyone tell me what they think has happened? Thanks Job1972

[maxwedge]

What year is the car?

[Job1972]

Gm. 93 Chevy lumina euro

[maxwedge]

Over the net, no way to pinpoint the problem, get it up in the air look for any related damage, connectors, dented pan for example.

[Job1972]

Ok. Thanks.