Trans shift problem

[79450sl]

I have a '79 450 SL. When the trans shifts from second to third, there is approx. a 2 second delay (rpm's jump up). If I shift it manually into third after the pre-set shift point, it shifts fine. I.E. if the car is in D, it shifts at about 2k rpm. If I leave it in 2, and shift to 3rd at 3k, the shift is smooth. I also experience very occasional problems when I accel from a stop. It feels like first gear is barely grabbing( rpms rise, car barely moves), then when it shifts to second, it shifts real hard. While first is slipping, i can shift it into first and it engages right away. Dont know if it makes a difference, but the car sat for about 4 years before I bought it. Had a trans service done, all fluids changed, etc.

Any help would be appreciated.


Thanks guys!!!!

-Rich
'79 450 SL
184,000