I have a 1998 Blazer that has been giving me the 1870 code off and on for a while. It came on 3 years ago, I brought it into a shop and they recommended a rebuild, they also offered a cheaper alternative to try which was pull the valve body and replace the TCC solenoid and do the reaming thing also. That is what I chose to do. I still got the code after the TCC work so I parked the Blazer for a couple summers. I got it going last year, I flushed out the fluid because it was bad, burnt, and smelly.
Worked fine for about 3 months then the 1870 came back. I have somebody that can rebuild it but I read on here that rebuilds can leave the VB alone. I may very well need a rebuild but what about the valve body? I would hate to have a rebuild done then find out I have something wrong with the VB. Can a good tranny shop tell?
I'm kind of ramblin because I don't know what to do. I kind of questined the 1870 code again because AllData says that it is emission related but it may mean what I think, it just turns on the MIL so maybe that is what it means.

 

Sounds like they either forgot to do something, or did it wrong. I would recommend a replacement valve body. A replacement valve body should have all of the updates already performed on it and should bolt-up/plug-in like the old one. I would give that a try before going the route of a full on rebuild that may or may not cure the problem, but will for sure cost more.

 

I agree with administrator I had this code on my jimmy got on line investigated problem found a trans shop that had a shift kit to install that would make the trans shift good and hard and get rid of the 1870 code,well I bought one install the kit and yes the trans shifted great nice firm shifts and about 20 miles down the road bam P01870 back again. Put a new valve body on it at 375.00 dollars plus a new TCC solenoid and problem was gone. Valve body is cheaper than trans rebuild.I don't know if you can install the valve body yourself or not but I think a trans shop might charge about 300.00 to install it. Still cheaper than a complete rebuild.

 

I was getting p1870 on the way home from buying my blazer. It was shuttle shifting and hard shifting from 1st to 2nd. I ordered the trans go shift kit and installed the new tcc valve along with 5qt and filter change. Drove the it all over and only had minor hard shifting toward the end of my drive when it got hot. Then I installed a tranny cooler and put Lucas stop slip. I will update after a really long drive but it seems to work fine. If I ever have more troubles I will figure out how to install the rest of my shift kit that only cost $40

 

For those that are throwing a P1870 code...it's basically saying your transmission is slipping (generic I know)...could be a multitude of solenoids...but the best bet (what I'm going to do) is change out the Transmission Valve Body which has ALL of the solenoids replaced in it. A re-manufactured VB (guaranteed) from Sonnax (bought mine off Ebay) runs for about $249 with all new gaskets, trans filter, solenoids, check *****, etc...all you need is new trans fluid and about 2-4 hours of time (depends on your mechanical prowess lol) on a level ground (lift preferred). I have a 2000 LT 4x4 4 door (179k miles) myself so this will fit mine perfectly.

Here's a link...hope it helps anyone else for future reference. Make sure you put the correct year for the valve body because '03 - '08 and up might have one of the connectors running up and down as opposed to sideways. Not sure of the specific subtly in differences there or which solenoid that refers to. Also the transmission filter could be slightly different as well.

http://www.ebay.com/itm/4L60E-4L65E-...xp=mtr

Thankfully you don't have to drop/move the exhaust crossover pipes to get the transmission pan dropped. The stupidest thing GM did was not give us a transmission pan with a drain plug on it. So while I'm in the process of changing out the valve body...I'm putting on a new transmission pan with drain plug for future and easier trans flushes. Here's a link for the pan I'm going with:


Hope this info helps