Occasional 3-4 Upshift Flare?

[Supercharged111]

This has happened maybe 3 times so far. I started putting some miles on the 99 K2500 and on just a couple of occasions it has revved up a smidge on the 3-4 Upshift. It has a fresh converter, new harness, and new fluid/filter in the 4L80. This is the only hiccup I've observed with the power train and 99% of the time it's not there. Just wondering what may be some potential causes?

 

[NickTransmissions]

This has happened maybe 3 times so far. I started putting some miles on the 99 K2500 and on just a couple of occasions it has revved up a smidge on the 3-4 Upshift. It has a fresh converter, new harness, and new fluid/filter in the 4L80. This is the only hiccup I've observed with the power train and 99% of the time it's not there. Just wondering what may be some potential causes?

How many miles on that transmission?

Do a line prrssure test then plug in your scan tool, take for a drive and look at shift speeds, especially at the 3-4 transition.

Sounds like OD clutch is beginning to wear out but diagnose it to be sure before yanking and overhualing it.

 

[Supercharged111]

232000 miles on the trans, it's definitely gone far enough to earn an overhaul. I think I'll take a look at the trims too, see if the trans is compensating for wear to meet a commanded shift time.