Turbo 350 issue

[mountainmotor]

I've got a Turbo 350 behind a Chevy 350. The transmission will shift smoth into the first three gears but will go into fourth only when coasting, when no power is applied. After it goes into fourth, as soon as I apply power it will shift back down to third, every time at any speed. Any thoughts on a fix or trouble area?? I'm an engine guy, not too much on trannies yet. Thanks in advance for any info.

BTW, this is older model equipment, no ECM, no wiring harneses, etc.

-John

[performabuilt]

Th350 transmissions do not have a fourth gear ?Are you sure thats what you have ?what model is the car or transmission
performabuilt