Transmission.. Or not?

[Chrishart749@gmail.com]

5.3 4l60e 2wd
120k
Fluid looks great at perfect level.
Have been having issues for quite a while.. All started last summer at wot when it wanted to shift it would sometimes stumble into gear.. Then it started this thing where it was like it wanted to jump back and forth from gear almost.. Then at wot the 1-2 shift would wind way up and bang into gear with a harsh scraping type noise. Since this wot hasn't happened so.. But I do have a harsh 1-2 shift and I experience the comman complaints found In the situation of a bad epc solenoid. But...
And this happens very frequently but never when cold. When it shifts into 2nd and I hold throttle heavy when it's abt half way through 2nd gear it'll hesitate/jump/miss.. Always at the exact same point.. It's a very quick brief hesitation that can be heard and felt. Motor does not rev up it actually sounds as if it stopped producing power for a split second. Not a slip.
Majority of the time I have all great shifts with exception of the frequent 1-2 shift with the previously described bump after the shift complained abt with a epc solenoid failure..any input?

 

[littleblazer]

Well... and don't take my word for it, but I was talking to a gm tech a few months ago about a sierra, newer and with the 6.0l as well as the 4l80e, but the truck will like half shift, then jump back then shift and like hunt between 1-2 and 3-4 multiple times within like two seconds. No harsh scraping noise or anything like that though. Basically he said what you said in that the shift servos are generally what causes this. And it doesn't happen entirely too often either. Now, I am not too sure how the servos work, but if it is a pressure driven system, like most components in the transmission, then when it is cold, the fluid is thicker, thicker fluid = more pressure and snappier shifts. Hot thin fluid could leak down pressure causing issues if something like a seal is worn. The truck has been doing this since 75k, just hasn't been enough of a problem to warrant fixing it. For the short time we ran a tune, (don't know if you do) the shits were back to factory, actually better. So basically I do not know if this is your problem, but my similar one was diagnosed as the shift servo not being up to snuff.

 

[Chrishart749@gmail.com]

Possible for the irritating 1-2 shift.. But there's definitely something somewhere broken or not functioning
It didn't always do any of this stuff

 

[DrData]

Well, did you ever find the problem? I've got a trans problem I'm trying to research.

 

[Mooseman]

Probably won't get an answer. He hasn't logged in since April and he's not subscribed.

 

[Mounce]

Could try pm'ing him though as that should send him an email. Or send an email to his username lol.