The 1870 code is normally the torque converter clutch slipping, but its usually not the convertetrs fault. There is a valve in the valve body (Called the TCC Isolater valve...I think) that controls TCC apply and it is a busy valve (meaning its always moving) so it wears out its bore in the valve body, aluminum bore-steel valve, when the bore wears out it allows fluid pressure to pass by instead of putting full pressure on the tcc valve, this causes the converter clutch not to get enough apply pressure and it slips, it only has to be a couple hundred rpm to set the code, and the only time you will notice a problem is during tcc apply, very hard to tell unless you have a tachometer, you may also notice a harsh 1-2 shift after a highway drive, this is because when the pcm senses the slipping it boosts line pressure to stop the slipping and save itself. Google P1870 and you will find tons of info on it, its very common, there's a simple fix that most tranny shops can do in a couple hours, they tear down the valve body and they have a special reamer that they use to enlarge the bore, then they replace the valve with an oversized one and your back on the road, the local shop here quoted me $150 if I brought the valve body in, if you have a ton of miles then you may want to rebuild the whole thing anyway but get the valvebody rebuilt, lots of people just tear the tranny down put in new clutches and seals and forget about or don't know how to properly inspect the valve body then the worn out TCC Isolater valve/bore allows the tcc to slip causing exccessive heat and then they burn up a fresh tranny, don't overlook this! One more thing, there are different torque converters for these transmissions so make sure you get the correct one if you rebuild the trans and replace it, they changed the clutch material inside them a couple of times over the years and they changed the computer program to compensate for the aggresiveness of the materials, there's a ton of info on the web so just do your research, good luck and let us what you do to fix it. Sorry for the long post but I had nothing better to do. Hope this was helpfull! :banana: