What's the problem?

1992 Honda Accord with 104,000 miles automatic transmission…was my mom’s car and has been consistently maintained and serviced and gently driven!!The car performs well until…about 3 weeks ago when it starting revving up and the D4 light stayed on even when I was in reverse. Idling high and Drove like the car was in high gear. Mechanic #1 checked the gear position switch and checked connection at Trans ECM. After unplugging and re-pluging in connector system functioned properly. And it did for about one week. then we were back to the same problem and it was clear that the car was not shifiting like it should. Mechanic #2
didn’t provide much feedback: he emphatically stated that it was a transmission problem and that the trans would absolutely need to be rebuilt: price quote: $3500 including labor. I’m scratching my head at this point & reaching for the aspirin…as little as I know about cars I’m wondering how a transmission needs to be rebuilt at 104k? Oh well…as much as I like this car, I don’t want to put in $3500 and hope for the best. Mechanic #3 is a Hondo maven…and he says it’s not the transmission…this is what he says: checked for cpdes; found none. reset Transmission computer by removing power to it resulting in the car running better and D4 light if off. He advises that we Wait & See if problem happens again…he suspects a possible electrical problem. Car does drive better and the D4 light remains off but when I get on the freeway the car seems stressed and noisy and when I deaccelerate, it’s noisy. I am waiting for the other foot to drop. Anybody out there got any hunches? Thanks all

While it only has 104,000 miles, the car is also 21 years old. Both age and mileage lead to problems. Don’t be surprised if it rally is the transmission. Since the fix is so expensive, why not get another evaluation?