1991formula305

Hello my 700r4 has about 1000 miles on it since rebuild 2 years ago one day on my way to work i suddenly lost 2, 3, and 4th gear. The trans would be fine in first but then when it was supposed to shift it would act like it went in neutral. Thankfully it was stop and go traffic and my work wasn't more than 2 minutes from the off ramp. When I got to work i checked the fluid and it was still a nice bright red and at the proper level so I thought it was too hot. After letting it cool down for 8 hours I went to go home but same thing happened only first then neutral. I decided to go to my buddies house because he lived closer and see if I could find the problem. On my way there I decide to see what would happen if I stuck it in second manually well it worked but would only shift at 4k rpm plus. When I got to his house I let it cool and checked the gov and it was fine and moved freely but a grinder was taken to the weights (not done by me) instead of the kit I supplied a few months later at a different shop. After I put the gov back in I took it for a rip up the street and I got back 2, and 3rd. It wasn't till the next day I realised I didn't have 4th or overdrive. Does anyone know what could be going on. Thanks for the help