I have a 1984 Spider with 78,000 on the clock. I have replaced the bushes on the gear selector rod, and have tried various adjustments but despite this I cannot change down into 2nd gear. Going up through the gears and into reverse are not a problem. I can pull up to a junction select 1st and go into 2nd without a problem. There is no crunching of gears. Am I facing a gearbox problem?