Bad Transmission? what is yiour opinion.
 

I bought a 99 Boxster with alleged bad manual transmission, here is what happens. Jacked car up and rotated the rear wheels, in neutral each wheel turns smooth, put car in gear and rotate one the other turns opposite direction, so far so good. I checked transmission oil its clean and up to level. Start car and it idles ok in neutral, put car in gear, any gear, and it takes half throttle to keep from stalling as I let the clutch out, acts like one wheel is dragging. The left rear will spin before the car moves it looks like the right was dragging but it turned ok when jacked up. After running 5 minutes and lifting the car now the wheels have a much greater drag. This all reported to start when the car was pulled a short distance by a tow strap from the rear.
I cannot understand the failure process here, what is wrong? I checked the brakes are not dragging, all four wheels turn. The right rear does look like it has greater camber, top of wheel inward verses the left side. I am pulling the transmission out to try a used good one. Anyone ever experience this issue? Is it possible the issue is with the right rear suspension but only with weight on the suspension and why does the drag in the drivetrain increase with just a little run time, it seems very odd? Am I missing something in my diagnostics?

When the car was dragged by the tow strap, I wonder if they wrapped the strap round the RHS drive shaft. If so, the universals / bearings each end of the drive shaft could be damaged - especially the one entering the gearbox.
A dial gauge on the drive shaft could indicate if the shaft is bent or misaligned when the suspension is loaded.

Try using reverse gear rather than 1st to isolate some parts of the transmission from others - same result? If so, then maybe damaged/binding spyder gears (or similar) inside transmission. If the car was pulled while in gear, these could have been damaged.

Look for leaks or strains under the car...

Don't ask Raby, he will have a nervous breakdown and go on a shooting rampage, lol

Sounds like the main or counter shaft is binding, possible the car was stuck in a ditch, at a bad angle without fluid covering the bearing or gear and galled or burnt it up during the attempt to remove said car from ditch.