I have a 1999 Blazer 4x4 with a 4L60E automatic transmission. The thing runs fine but when I go up a hill steep enough to make it downshift it won't upshift again untill I crest the top of the hill and and and go quite a ways on the flat. I have a cheap code reader and I am getting a code 1870 which I guess has something to do with slipping. I swapped tranny's with one that I know came out of a working blazer and I still have the same problem and still gat the same 1870 code. I also changed the valve body with a rebuilt one durring the swap. I'm at my wits end with this thing. Could it be a vss problem or something electrical? I have visually checked the wiring harnesses and connectors but found nothing wrong. any help would be greatly appreciated. Thanks.

 

Welcome to the forum!

I found this on google if it helps at all.
http://www.gearsmagazine.com/images/...2006_05_80.pdf

I am sure someone here that is more familiar with that particular problem will be able to help you.

 

Thank you for your help Mike. Thats an interesting article. At this point I'm willing to try anything.

 

the code 1870 is a trans component slipping check to see if you have tcc engagement if not then the tcc regulator and isolator bore in the valve body needs to be reamed and new valves put in

 

Thanks for the reply. How would I check to see if I had tcc engagement? I replaced the vale body with a rebuilt one. I guess I got taken.