P1870 code ??

Hi I'm new to this forum
 
We just bought a Very clean. one owner 1997 Express convertion van with only 51k miles on it. The van is in mint condition and runs great. We love it! The only problem we have with it is the "service engine light" comes on. I had a shop read the code and they said it's a P1870 code. Talked to another guy and he said that's the transmission converter clutch slip code. This might explain to it shift hard from 1 -2 gear?
 
Anybody else have this problem??

I got a 99 chevy express i recently got and i got similar code but not in numbers it said rapid misfire. the person who i got the cold told me the transmision is fine only thing need to change to fix the hard shifting is the torque converter, he told me its no good and the last guy that put it on left a couple of screws loose which is shifting hard. so just check your torque converter you can climb under your truck with light and look around too see if you see any thing out of place thats not suposed to be.