[shorod]

In both of the posts above you specifically mention reverse. If you start it up when cold and put it in Drive will it also do it, or have you not tried that? If only in reverse it would point more towards a transmission issue. If it also will do this in Drive, then it could still be a transmission issue, but it's more likely an issue with the engine, maybe an Engine Coolant Temperature (ECT) sensor issue or IAC issue.

-Rod