newbie with old(s) problem

The problem of the hour with my 1979 delta 88 is a new one to me. I was cruisin on my way back to school when it seemed like the car came out of gear, I let off the accelerator and got back on and it began to pull like normal. About 20 mins later the same thing but this time I had to pull over. The trans fluid was ok, It just got a major tune up. It still has reverse and drive but engine just revs after 20mph. I am praying it is not trans problem. I just hit 91,000 mi.

I greatly appreciate any suggestions or advice.

It's hard to tell for sure because tranny problems aren't easy to diagnose without looking at them. I'd suggest dropping the pan and look to see if there is any debris in it. There is also a possibility of the modulator being faulty. If the transmission needs to be rebuilt, luckily the TH350 is easy to find reman and often cheap for parts. I'm going to assume that you have a TH 350 Trans, To be sure engine VIN codes F,Y,or R have a TH350. Cars with VIN code A,N,K I can't be sure. I had just recently priced out a TH350 for my 78 Olds 88 for a price of 412.88 from our local Advance Auto. The number for the part was 350B6. That was the code for the Olds bellhousing.