I was told I need a new transmission, but it seems fine?

Hello,

Can you please be more specific as to why the shop wanted to replace the transmission?
What issues did you encounter?

Any oil leaks? Drivability issues?

Cheers, Boris

The vehicle was not driving correctly, it would not turn over or accelerate.
The vehicle would stop and go while driving as make it almost impossible to drive over 40.
Two days after I left the mechanic the truck returned to normal driving.
No stalling or shaking.
The light comes on and off but driving without issues.

The mechanic said it was a transmission and needed a new one at the same but ever since it's been running fine.

If a transmission goes bad, doesn't it mean the car will no longer drive until it's repaired or replaced? but nothing was done to it but the diagnosis.

Hello,

I do agree that a mechanical failure in the transmission would manifest itself in driving/gearchange difficulties.

You mention that the engine light comes on and off. This means that there will be fault codes stored in the management system. Would it be possible to have a CAN scan done and then post the fault codes on here?

This would enable us to give you better advice.

How to carry out a scan:
https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Most auto parts stores will have an OBD-II scanner on hand to check the OBD-II PID service codes and will do it for free.

At a local auto parts store such as:
Advance Auto Parts.
AutoZone.
Napa Auto Parts.
O'Reilly Auto Parts.
Pep Boys Auto Parts.

Cheers, Boris