My '99 s10 Blazer auto 4.3l v6 4x4 sometimes has a really hard 1st to 2nd shift after driving a while and outside temps are over 100F (like in Vegas this past weekend).

Once it didn't want to shift from 3rd to overdrive at hiway speeds. (outside 106F)

Trans fluid looks good (had fluid and filter replaced 3mos ago). Read in DIY forum to check the fuse, will do that in the morning.

Really seems to happen when outside temps are 104-6 or higher. Or after driving for a long time (4hrs). Last night I waited until the sun went down in Vegas to get cooler weather for the drive back to L.A., trans ran fine until close to home (by then 72F out) and it was hard shifting again 1->2.

Can anyone give me any ideas? where I should be looking?

Thanks a lot!

 

Any P1870 Code??
Just talked to a trani guy about almost same issue. Mine does it all the time but only after driving for 20 minutes. So trani is hot.

The Trani Guy says there is a " I forget the name' in the Valve Bodyof the 4L60 trani that is made of soft metal and wears out at 100K miles-ish. They bore it, put in a sleeve to bring it back into spec. and that should solve the issue.

 

Thanks Tony!

I just got the code last night and it is P1870 - Trans Slipping

 

http://www.batauto.com/Forums/index.php?topic=4681.0

http://www.batauto.com/Forums/index.php?topic=4013.0

Read what TRANSMAN has to say. he sounds like he has a clue

 

So I had a local tranny guy look at it. Test ride with the scanner showed some slipping in the 5-600pm range, but temps were not in the 100's.

They dropped the pan and looked inside. Didn't look too bad they said, but fluid wasn't good - tho I had it replaced not long ago.

So they did Regulator Value Kit and Apply Value. New gaskets and fluids, along with Lubegard.

Scanner now shows near zero.

So far so good - next week I'll have to drive out to the desert and test it in the high temps (fingers crossed).