2-3 shift on an "A904-LA" question.

The TF ratios are 2.45-1.45-1.00 and the splits calculate to .59- .69
so then, at Part Throttle, going to 50mph, at a throttle setting that outshifts first at say 2800 rpm, the 1-2shift will be at ~26 mph with an rpm drop to ~1700 rpm. which is a drop of 1100rpm
so then, now you are in Second gear at 1700 rpm. Continuing at the same throttle setting, and if the VB is properly calibrated, the 2-3 shift should also occur at 2800...... which will be at around 45 mph, with the Rs dropping to ~2000, a loss of just 800 .
depending on the actual stall, the convertor efficiency, the TV pressure setting, and most especially, the 2-3 shift command calibration, these numbers could be from a little to a lot different.
I have only rebuilt about a dozen or so TFs but have yet to see the 2-3 shift happen where I wanted it to, compared to the 1-2; they have always shifted early.

BTW your tach looks to be about right.
My calculator spits out 50=2016 at zero slip.
2150 would be 2% slip, sounds very good.