I bought this 2000 blazer with bad intake gaskets so i never drove it till after i fixed them, now its running really good but im having a TCC lockup issue like ive seen described a lot on here, ive been searching for a while but cant find specific info that maybe a seasoned tranny guy would know. Heres the history, 145,000 miles, just did intake gaskets and distributor gear, looks like it has newer plugs wires cap and rotor but i did not replace them, replaced TPS right after i got it running because it was bad, showed bad on the scantool, huge dead spot, cleaned MAF Sensor, it was pretty nasty but i took it out of the housing and did a good job cleaning it, i think thats all. Heres the issue, having the TCC lock then unlock back and forth at 50-55 mph under light load like others describe but i can also feel what seems to be TCC locking and unlocking at 3/4 to full throttle in the 3500 - 4500 rpm range, it doesnt feel like a slip, feels just like the 50-55mph issue only under full load at high rpm. So my question is, does the VCM lock the TCC under full throttle acceleration and does this sound like the common worn out valve in the valvebody issue or maybe electrical? Im just trying to decide how major of a first step to take, fluid and filter (fluid looks pretty good by the way), valvebody rebuild, solenoids or just pull the tranny and go through the whole thing, sorry my first post had to be this big huge thing but ive been lurking for the past two months since i bought this thing. Thanks for reading, i really appreciate your time and input

 

It's normal for them to unlock even under light throttle and especially at 3/4 to full throttle. I wouldn't worry about it unless it starts doing it at a constant speed.

 

What this is doing is not normal, if i couldnt see the tack it would feel like a bad misfire at the 50-55mph range, it really doesnt have to be under much load at all, if you just gradually pass through that speed range it will lock and unlock at least 5 times and you will feel the bump, noticably. When it does it under heavy throttle its while accelerating hard holding the pedal in a constant position before it shifts to 3rd you feel the same kind of bump around 3500-4500 rpm, you can watch the tach jump up and down a few hundred rpm when it does it, then it comes past that to 5000 or a little higher and shifts to 3rd just fine. My wife drives a 2000 astro with the exact same drivetrain and it doesnt do anything like this, ive driven that a lot and never had anything like this go on, im sure i will sometime though!

 

I would start with a complete ATF flush (not just fluid change) and then the TCC solenoid. I had the rpm fluctuations at lower rpms (50-65 mph in overdrive) but never had it with higher rpms.

 

did change help did you ever solve the prob mines doing same thing