Early shifting on a 190e 2.6

[NDP 2.6 190E]

1991 190e 2.6 with 112k miles

Car drives fine except that when pulling away, the shift between 2 and 3 occurs at about 1500 rpm - which is too early in my opinion, and causes the car to bog down.

The other gear-shifts seem to occur at about 2000 rpm with the same throttle position.

I can delay the shift by holding the selector in 3, or by accelarating really hard - this causes the shift (from 3 to 4) to occur at anything up to 2800 rpm.

Is there an adjustment that I can make?

Background
Had the transmission rebuilt approx 2 years ago, but I didn't like the way the 'independant' shop kept piling on the extra charges. Also, a follow-up diagnosis suggested that a rebuild may have been unnecessary - so I won't take it back there.

Thanks,

Neil