major transmission isssue
 

issue with my car - '11 R3 - transmission pops out of 3rd and 4th gear, was happening infrequently, but recently very regularly,
adjustment procedure done as outlined on rx8club, to no avail
So I took it to local dealer where I purchased the car new- he replaced synchros and a shift rod, new fluid, and it was fine driving around town
On the highway, at speed, yesterday, it suddenly locked out of all gears except 4th and wouldn't engage any gears
Pulled to the side, could not engage any gears at all, so car was towed to dealer
While loading onto flatbed, car made awful groaning sounds and gear was very difficult to engage -
Then the next morning, dealer says the car runs fine - no issues at all-
I'm assuming driving at speed messed something up, and after cooling overnight , it's now fine -

Any thoughts on how to proceed -
Car still under warranty

Any advice/insight would be appreciated

It could be many things, clutch plate, the computer, wrong fluid, and of course the list goes on. I once broke a small plastic piece internally which lines the stick up with each gear. It was a 50$ fix but it would only go in 4th as well. (That was the first time I tried learning manual haha)
Have your shop take her on the highway and see if they can figure it out. Let them drive it until they encounter the issue. Hopefully they can figure it out. There are just too many things that may be going on in my opinion.

Would it shift with the engine off? If so its clutch related. If not transmission. I don't know that year range but, id be very surprised if the trans is computerized at all.

Popping out sounds like bent shift forks. They don't get fully engaged and can pop out. That comes from slamming the gears too hard. Look into a syncro saver it will prevent the over shifting. I don't know if they make them for 2011's

Btw since you have an '11 this really shouldn't be a concern, but just for the sake of reference:

https://www.rx8club.com/series-ii-te...2/#post4301049