This is a two part question..My 2000 trailblazer 4x4 shifts normal in temps below 80 degrees or so. After driving at highway speeds for 30 minutes or so..if i slow down to a stop and take off again i get a pretty hard shift from 1st to 2nd gear. 3rd and 4th seem to be ok maybe a little sloppy but not a hard shift like the other.What would cause this. Fluid levels are ok and temps seem to be normal at least in the radiator.Trans was rebuilt at 98,000 and just had a fluid change recently.Also no trouble codes for trans.If i stop and park it for a while it shifts normal again which leads me to believe its a temp thing goin on..Stumped
My next question is about my o2 sensors..All 3 replaced with a new y pipe..Computer give a trouble code of "no o2 sensor activity bank 1 and bank 2"
I stripped the wires back and did a voltage check on the sensor itself with the truck running and its reacting as it should to heat. I reset the codes evrytime i drive the truck.When I turn it off and back on and start driving again the codes are active again. What would cause this.? Thought maybe the computer needed reprogrammed or replaced not sure..The effect of this is my gas mileage has gotten a little worse..ANy input would be greatly appreciated..

 

Im not sure about the o2 sensor problem but i recently dealt with the same trans problem, a hard 1-2 shift is associated with 2 things a worn tcc control valve in the valve body, wich usually throws a p1870 code for trans slippage, or a check ball in the valve body that has wedged itself into the seperator plate i had both problems and a after dropping the valve body and replacing the tcc valve (which i assumed was the whole of the problem) i found the check ball jammed in the vb seperator plate 15 bucks for the valve and 25 bucks for the plate, it can be done ez enough if you have any auto experience gimmi a minute and ill give you a link to a thread discussing the repair

https://blazerforum.com/forum/engine...-so-far-52746/

also you can go to youtube and search 4L60E and see many vids on the removal inspection and install of the valve body, there is a good vid also in the first post of the above thread

 

Thnks Mr Monkey.Great video And what he was saying about the fluid thinning out with the heat during driving makes alot of sense.Transmissions are not my forte but this repair i think i can handle.Now just locating the kit and ill be good to go maybe.

 

Locate a Dealer Near You will get you the valve i imagine they may have the separator plate as well mine was a trans-go plate careful that hot trans fluid will nuke the plastic parts of the wiring harness i broke every clip i took loose another 65 bucks for the harness

also when you drop the vb then the plate there is anouther check ball aside from the seven the videos on youtube will tell you about it is on the top side of the plate the others are all in the vb, and there is a spring and small rod (parts of the 3-4 accumulator i believe) that may fall out at the same time from above the sep plate. i did mine last week so this stuff is still fresh in my head

in this image 91, 46, 43 may fall out at you so watch for them