09 columbia DDV 1500 tops

Sounds like a parameter in the ECM settings. Plug it in and look at progressive shifting RPM limits would be my loose guess.

 

Normally companies would set up progressive shifting limits for fuel economy, but in reverse to what you described, i.e. -

Low range 1-5 gear, limited to 1400 RPM,
High range, no limit or 1600 RPM for example.

This is done (hopefully along with training) to encourage drivers to conserve fuel by using minimum RPM whilst upshifting.

If you had the described work completed by a mechanic/shop, I'd look over their shoulder whilst plugged in and set those parameters as you see fit for your operation - they may have flashed or reset your ECM parameters.

 

Parameters set incorrectly.
Second, had a truck years ago that only in 3 & 5 & 8 &10 truck would hang no higher then 1,500 on bumps it would hiccup, found wiring for reverse switch was routed tight on the shift lever caused the wires to rip back and touch . At that time I had no laptops to see this but this truck limited rpm in reverse