[83cutlass]

Here's my experience with this DTC 1870 on my '95 blazer. So my truck had that code and the previous owner just drove it for a while until the 3-4 clutch burnt up and the trans no longer had 3rd or 4th gear. So they gave me the blazer for free and I rebuilt the transmission. I drove it and knew the converter wasn't locking up when the trans was warmed up and I was right when that 1870 dtc came back a short time later. So I ended up replacing the valve body and now the problem is solved. Hopefully you'll find this story helpful.