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Remember your 3/4 ton is a truck and not a passenger car. The trans needs to shift firm so that it does not wear out when it is working hard. The firmness of the shifts can be adjusted in the shift rods. Small adjustments can make a big difference in the firmness of the shifts. It can be adjusted so that it feels like it is slipping into gear, unlike the banging into gear you are now feeling. Remember it shifts firm for a reason.
Also the firmness is regulated by throttle pressure. The harder you accelerate the harder the trans will shift. Do a search for the online chevy manuals and you will find instructions on how to adjust the linkage.
hydro manual If the insides of the trans are working properly, the shifting is all related to the linkage and throttle pressure.
Part are available through a couple of vintage trans repair parts houses here in the States.
