Low revs after transmission rebuild
 

Hi. First time posting in years. 2004 4.6 v8 140800 miles.
A bit of a long story. Last week I had my transmission rebuilt by a reputable independent shop because the dealership said there was an internal failure causing the truck to not exceed 30 mph. Yesterday I went for its first long drive at freeway speeds since the rebuild. Transmission shifts smoothly and quietly but the revs never go above 2100 rpm. It has no problems going up to 80 mph (fastest I went due to traffic) but even when I press the accelerator down pretty far, the most it'll rev is 2100. Before the rebuild it would rev faster when punching it. Cruising before and after the rebuild at 65 mph was about 1800 rpm. Did the transmission shop break something or adjust the rev limiter (if it has one) or could they have rebuilt the transmission with different gears than before? Torque converter was rebuilt too and rear main seal was replaced. Other than being a little slower accelerating and lacking a little power going uphill, the truck runs great after the rebuild. Should I be concerned about this?
Thanks

How high will it rev in manual 1st and manual 2nd with wide open throttle? Note - if it hits 5 grand, back off, you don't need to wind it any tighter.

I'll need to try it after work on an empty road. Too much traffic lately. Luckily today I got it up to about 2600 rpm and seamed to be pulling stronger. Maybe it just takes time/miles to "break-in" the new parts.

I still think there is something wrong with that. 2600 is what a MCI J4500 bus does at WOT.