Volvo - 240 :: 1993 - Unable To Get Manual Transmission Into Gear

I was recently driving my 1993 Volvo 240 wagon over the Bourne Bridge in bumper to bumper traffic (surprise!). Traffic was moving at 3-5 mph as I navigated the rotary and ascended the bridge. Needless to say, I was developing leg cramps as traffic crawled up the steep bridge incline. Once I crested the hill, I shifted to neutral (still 3-5mph to coast down the decline and give my leg a rest. After coasting for a few minutes I attempted to shift into second gear to re-engage the transmission.

I was unable to slip the gear shift stick into any gear! I continued to make sure that I was depressing the clutch all the way to the floor, but still could not muscle the stick into a single gear (by the way, I never smelled that "burning clutch smell"). After about a minute or more of mental disaster planning, I finally coerced the shift into third gear. A minute or so later, I was able to shift into second gear which got me around the accident causing the delay and onto the highway. From that point on, I was able to shift normally for the remainder of the 2 hour trip. What happened and what could I have done to solve the problem? (The car is now at the repair shop where they are equally perplexed).