We all know that the transmission bug is causing some major problems with tunes that require moving the Final Gear after also moving the Max. Speed (Auto Set) slider. This Corvette Convertible (C1) '54 tune requires such manipulation. I believe I found a work around, at least worth trying for now. You'll be able to set all the parameters in the tune and it will not reset to default on you. Here's what you've gotta do:
Set final gear to: 3.360
Set top Speed @: 137 mph
Set Individual ratios to:
1: 3.280
2: 2.120
3: 1.570
4: 1.250
5: 1.000
If you set the Final Gear FIRST and then move the Top Speed slider and set your individual gears, it will not reset to default when you hit the track. The tune initially called for setting the top speed to 124 mph, but you wouldn't be able to move the Final Gear after setting the individual gear ratios because of this bug.
I've found this work around for other tunes as well (particularly Ridox's tunes which I have most of my cars tuned with). As long as you set the Final Gear first, before doing anything else, you should be okay. The problem is, you'll have to hunt for a different Top Speed setting to use then the one listed in the tune because we're doing things kind of backwards. Anyway, give it a try. I think you'll be pleased. 👍