my car is programmed for 3:42 gears but i am running 3:73's

would this cause my car to shift at 5700-5900 rpms instead of 6300 rpms like it is programmed too?

PS: i posted in genral tech but didnt get a response and thought this might be a better place to ask

 

Since shifts are based on a TPS% vs. MPH table, I would say it's not going to shift properly until you get it programmed for the gears. If it thinks your car is going faster than it really is, then it will shift early.

 

Yep, it takes a few tries messing with the tranny tables to get it right.
When I did my LT4 engine swap, I thought I'd just copy over the tables that were in the original TBI PCM and make them the same in the LT4 PCM, but that did not work since the LT4 put out much more hp and reacted completely different than the original motor....taking the stock f-body tranny tables did not work either due to the weight of the truck and the gearing.....after 2 years of tinkering with it, its almost exactly right except for the 2-3 downshift when punching it if already cruising at around 30mph or so in 3rd gear.