Another P1870 code on a 2002 Envoy

[Drec]

My 2002 Envoy has an issue that started yesterday while shifting into high, the RPM's went high. It through a P1870 code and the “Check Engine Light” appeared. Then it didn't want to shift into high at all. Today I drove it around a little, then it started doing the same thing into 3rd, then into 2nd. I drove it down the street a few minutes ago, and it shifts normally into 2nd, but nothing else just revs.

I’ve been looking on the web and it appears that it could be a number of different things. Up until this point, there were no problems with the transmission. Except that I was noticing a surging in high gear and sometimes it would play shifting back and forth between 3rdand 4th.

Any ideas?

 

[Sparky]

For kicks (I just thought of this) try clearing codes, and see if it shifts back into other gears again. If it does, the computer is just making things worse. Installing the shift kit that I've mentioned should then fix it.

If clearing the codes still does not give you 3rd gear back, then, you've got band burn-up going on as well, I'd suspect.

 

[Drec]

Is there any info that would be lost if I cleared the code? Or would it even matter?

The fluid does need to be changed, so as soon as I can get it into my garage and on the hoist I'll do that. I'm sure I'll have the pan off and could change out some components while it is apart.

 

[Drec]

I cleared the code and drove it. It shifted normal from 1st to 2nd. When it came time to shift into 3rd, the RPM's went up like it was in neutral. I tried this a couple of times and it did finally shift into 3rd, but wouldn't shift into 4th, it tried to shift back and forth, just like it did before the problem started.

 

[Mooseman]

Shift solenoid? But the P1870 shouldn't prevent it from shift into 3rd or 4th. In fact, it has to be in 3rd or 4th to engage the TCC and if it's slipping to get p1870 to set.

From memory of other threads, when it won't shift like this, the tranny is done.

These threads are similar:
https://gmtnation.com/forums/threads/2003-trailblazer-transmission-issue.12360/
https://gmtnation.com/forums/threads/trans-slipping-easy-fix-or-toasted.16708/

 

[Drec]

The transmission was shifting fine, except it would drop out of 4th and into 3rd and go back and forth while you were cruising with a light touch on the throttle otherwise it would stay in 4th and be fine. I thought that it was the throttle that was doing it, so I was doing research on that. Then yesterday while it was shifting into 4th, it through the code and slipped. It wouldn't shift into 4th at all. Then when I drove it earlier today it wouldn't shift into 3rd and occasionally 2nd.

Then a little while ago after clearing the code, it shifted normally into 2nd. Then trying to get it to shift into 3rd, it just revved. It did this a couple of times and then it shifted into 3rd and tried to shift into 4th like it was doing earlier.

 

[Drec]

Looks like I'll be taking this to a shop to fix; which is a new experience for me. I stopped by a recommended shop yesterday and got a quote of $2300 to $2800 to fix it. Sounds like they will be beefing up and it will have a 3 year warranty. This transmission shop has been a local family owned business for over 40 years.

 

[Drec]

Picked up my Envoy today, and $2900 later, it works great. Something I'm not used to doing, having someone else work on my car. They replaced all of the plastic and normally weak pieces in it ( clutch packs bands and etc.).

 

[Sparky]

Sounds good, should be set for a while now then.

 

[Reprise]

I know (from experience) what that feels like. Our thanks for not giving up on the platform & helping to keep another 360 alive

 

[Drec]

Hopefully, with the rebuilt transmission, this should last a long time. The car/truck is is good condition with only 120k on the clock, so should easily last another 120k.

These have really a nice motor in them and have thought about putting one in my 47 Chev.

 

[paul2005tb]

i installed a transmission cooler a few years back, i am hoping it helps to keep my transmission running smooth for another 200k.