2000 GMC 3500 454 / 4L80E no reverse

[alabbasi]

All,

I recently bought a 2000 GMC 3500 dually. Nice truck in overall good shape but the transmission appears to have lost reverse (barely moves). It shifts perfect in all forward gears.

It appears to be a new car trade, clearly a Texas truck as all the service records were neatly kept in a Whataburger bag.

Is a complete tear down in order or is there something I should look out before sending it to a transmission shop.

Thanks