Here's one for all you s2000 experts.

Had a friend come over today to diagnose an issue where when he puts the car in reverse the car travels back a very short distance then just gets stuck.

Jacked the car up and the rear wheels turned fine.

Took the input shaft off the diff to test the diff and transmission independently, diff turned fine, went to turn the transmission and it would turn freely going one way but wouldn't budge going the other way at all by hand, that's with the gearbox in neutral.

There is no issues or noises going forward in any gear just the lockup when reversing.

When you rev the car a little it does seem to brake loose and revers again but it certainly doesn't feel right, other times its so stuck that the engine stalls.

We drained the transmission oil just to check it and be safe and it was good oil clean and nothing odd came out.

Not something I have ever come across while working on these cars.

 

EDIT. My idea was wrong...