The P0767 code is a shift solenoid code and is the likely culprit in your shifting problem. The solenoid is an electro-hydraulic switch that guides the transmission fluid through the valve body.
The P1450 code is a fuel tank vacuum code and is likely unrelated.
The problem here is that the codes mean absolutely nothing without a full diagnostic performed. I cannot tell you what parts to replace, as I do not know what has failed. To properly diagnose this, the shop has to perform extensive tests that typically cost $100 - $200.
It could be a failed solenoid, could be a clogged valve body, could be a bad wiring harness etc. Take it to a transmission shop and have it diagnosed. Do not drive it though, have it towed, as driving it may lead to internal clutch damage -- if the damage isn't done already.
Hopefully this provides some guidance.
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Wednesday, June 29th, 2011 AT 11:01 AM