tb 350 will not shift into 3rd

[spiner5000]

never had a problem with this transmission till the other night the governor gear wore out so i drove it home probably 5miles replaced the governor and not it gose 1 2 but will not go into 3rd unless i put it in neutral for a few seconds then back into drive it works for awhile till it down shifts then its stuck again i replaced the oil and filter their wasn't much crap in the oil pan some sediment that was hard thats probly from break in long ago wat could be wrong with it

[tobiahr]

check for loose or cracked vacuum lines

[spiner5000]

did that it just started this one night after starting it replaced gov works for a few miles then poped out of 3rd to second pulled the trottle pressure leankage at idle a few times and worked great for 20miles so i keeped doing it and its worked for 3 days somtimes has problems shifting back into 3rd from passing gear now this truck sat in a garage for years since the 90s guy used it to plow his drive way it had 79,xxx miles when i bought it 78 400sbc 4x4 k5 blazer Cayenne out side rusted to hell from salt on the roads but not to bad clean motor very clean interior has all the stuff that came from the dealer like the tag that hangs from the hazard light button saying how to operate and the pin that gose in it to hold it so its a nice truck but idk