Odyssey 2003 - Transmission issue , Need advice
 

Hi, I have a 03 Odyssey with 126K miles on it, A month ago while on a highway it suddenly Engine Light came on and the went into "Limp mode" , The car would not accelerate over 40-45 mph and RPM was high. I drove it back home and found that the reverse gear will also not engage. Next day I drove to nearby honda dealer and they scan the code to be 0740 and 0780 and told me I need a new Transmission and cost be $7000. I wanted to get a second opinion and so got my car towed to a "AAMCO" shop. To my surprise when they took it down from the tow truck the reverse gear started to engage on its own and the car started running smooth again. The AAMCO mechanic did not have a good explanation for it but kept saying that I still should get transmission changed and I will start to have issues again once I go over 50mph.

Its been a month and I have been driving the car around in the downtown area. I have not had to go over 50mph and honestly I did not try to experiment either because I was scared if I will have the same issue again

My questions and I would appreciate any expert advice
- Any explanation why car started to drive fine again by itself and without any repair

- Is it really logical that I have no issues as long as I drive under 50mph but will have trouble if I go over ? That seems odd to me. Is this true ?

- Last time I had transmission fluid changed was at 90K miles. AAMCO guy also told me to not replace it now as that may cause the transmission to fail again. Is this true ? What should I do ?

- Any suggestions what should I do ? I will off course like to get as many more miles out of the car as I can but also not looking to spend 5K to get a rebuilt transmission