2nd gear won't engage when hot

[rezanourai]

First day on track with the car (at laguna seca) and while the weather is awful today it's a good enough chance to shake out any major issues with the car.

After the first 20m session, I noticed now my 2nd gear refuses to engage once I've warmed up on track. Once the car cools down a little, 2nd gear works perfectly again. All other gears (well at least 3 and 4, don't really use 1, 5, or 6 on track) seem to work fine.

It doesn't grind or anything, just doesn't "notch" into gear. The shift throw is about normal, just no engagement

Any ideas? I just changed transmission oil last month fwiw, my gut feel is either transmission temp getting too high or shifter/cables/ends are too worn (all original 20 years old)