I have a 96 4.3 blazer with the newer style 4.3 automatic transmission, and it has 131,000 miles on it. I have been having a problem with the transmission shifting in and out of overdrive very frequently, after a few miles of driving especially when going down any kind of slope/hill or when i'm not giving it gas. When it does this I either give it gas until it shifts back into overdrive or coast until it goes back into overdrive. It also seems to slip into each gear (revs high then slowly grabs the next gear) when I accelerate. I have done a transmission flush twice in three years, more often then nessecary but I got to do it free working at a Valvoline Instant Oil Chance quick lube store. I did the trans filter at about 123,000 miles but the neck on the filter seemed to fit in kind of loosely into the transmission. Any chance that if it came loose that it cause these problems? Anyone that has any other ideas of what could cause this please let me know!

Thanks!!

 

might bea badshift selenoids theres's 2 of them isinside the transmissionyou can change them just by removingtheoilpan

 

I read on another post that a low engine temp from a bad thermistat can make your transmission opperate incorrectly. I just changed the thermistat out and now have the correct engine temp and now the transmission doesn't shift in and out of overdrive when driving anymore. Thats one part of the problem that was fixed but it still slips into gears when I get on it. You mentioned shift silanoids, is that the same as a clutch pack?

 

What color is your tranny fluid, and what does it smell like.