Just hade the guys at NAPA hook up my blazer to the computer and Im getting a P1870 Code. I know what the code is, but I dont know what needs to be done in order to fix the problem. Im most likly going to have to have someone else fix the problem, Im just wondering what I can expect to pay to fix this issue. Thanks Andy

 

I can just about guarantee you that any shop you call will say, almost to the word, "Well, we won't know until we get inside the tranny."

 

My '97 gets that code a lot during the winter months. The blazer will shift fine for awhile and then start to shift like I've got a shift kit installed set to "race". Another problem that starts right after is I can't shift out of park with the engine started. I have to pull the center console boot cover off to push that lil white button in while I shift out of park. I have changed my nuetral contol switch and that seemed to have fixed things so far. Now I'm waiting for the temperature to dip down to see if it fixed the P1870 issue. My fingers are crossed. I was told initially that the valve body might need to be replaced by the local trans shop.

 

99% of the time it's the TCC apply valve in the valve body of the transmission. It's a steel valve in an aluminum bore, it wears the bore and causes bleedby of fluid. I paid a shop $450 to rebuild the entire valve body and put a transgo shift improver kit in. and then a week later i had to replace the 1-2 and 2-3 shift solenoids (but that's another problem unrelated to the 1870.

Here's the transgo kit. TransGo | 4L60E, 4L65E, 4L70E and 4L75E: SK 4L60E

and here's a little video

 

Thanks Mike98 for the info. At least now I know what the approx. price might be to fix the 1870 code.