My in-law's 1985 accord auto tranny is acting up. He says it will shift into the first few gears just fine, but that when it goes to shift into high gear (at approx 45mph) it's like it's just not there. Instead of shifting into high, it acts like it's been shifted into neutral (the rpm's will jump to redline until he lets his foot off the accelerator).

This car only has 85K original miles on it and was not driven hard at all. I'm wondering if this is a problem with one of the tranny solenoids being shot, or plugged up. Any ideas on what to look for (I will be doing a tranny drain and fill tomorrow), or does it sound like the tranny is just shot?

Thanks for your help.