i have a 89 firebird with a 305 tbi w/ 700r4 trans and was wundering if a puting in a 350H.O. would i have to change the trans and with the 700r4 is it normal to have it shift out of 4th into 3rd crusing at about 60

No, you wouldn't hafta change the trans. As for it downshifting, you need to go into more detail about the circumstances. Does your car have 2.73:1 gears? That can contribute.

yes you can use a 350 and yes it is unusual to drop out of 4th.
but that year did have a problem with losing 4th gear. 1990 and 91 had a slightly different set of insides and it did not do that.

i justa had it rebuilt about 4000 miles ago and i dont no what the gear ratio is i belive that its just a stock trans and its not the formula or eny of those i hope that helps and if i were to replace the trans what would be the best 4 or 5 speed manual that would bolt up to the 305 and 350

i was also wondering what would i have to do to convert from a throtle body to a carb

The easiest swap is a T5. as for TBI to carb, this is technically illegal, so here's an "off-road-use-only" parts list. Non-computer carb, non-computer distributor, carbureted intake manifold, carbureted throttle bracket, carbureted throttle cable, and until you swap your automatic to manual, carbureted TV bracketry, carbureted TV cable, and an alternate way to lock the converter, such as the PainlessWiring kit.

why is it illegal to do

Federal emissions laws. But not every town has emissions testing to get your registration renewed, so lots of people get away with alot of technically illegal stuff.

i dont no of eny place in michigan that dose emisions testing

I know detroit area does.

what about west michigan

doesn't matter, you're missing the point.

one of my cousins worked for gm dealership. they had problems with that trans for years. he always said keep it in 3rd in town because it tended to jump back and forth between 3 and 4 all the time. only use 4th for highway.
then in 90 they seemed to have fixed the problem and everything was working well. dont know what gm did but they got it fixed.
but what ever it was it had to do with jumping back and forth between 3rd and 4th.

it jumps back and forth on the highway to

could you ask your cusin what was wrong with it

dose eny body no what can be changed to fix the trans problem

That's a Transmission and Drivetrain forum topic.

it sounds like the tv {kickdown} cable is to tight .I read many chiltons and they say to push in the release button pull the cable back toward the fire wall away from throttle body then let go of the button and open the butter fly all the way and it self adjusts but i found it still a little tight the way.so i do it that way and just move it a little loser until the problem stops

thanks i will try that when i get a chance but i dont get many chances to get the car on a lift to do that