Shifting issues

[NDIinspector]

Multiple time i have experienced a what feels like a delayed shift from 1st to 2nd when leaving my house.  It usually happens the first time I drive my truck for the day and just feels like its shifting real slow, no kick or anything like that.  A couple days ago, in the same situation, I had a very hard shift from 1st to 2nd, and from 2nd to 3rd.  Hard enough to spin the tires on my dirt road, I was barely pressing the gas and it felt like I ad a shift kit installed and the gears where slamming together.  The hard shift has only happened one, but the delayed shifting is every couple days.  Any ideas what it could be?

 

For reference, I have a 5.3 w/ 8 spd transmission.

Edited July 16, 2021 by NDIinspector

[Steve-2019]

There are multiple/many posts on this forum with this issue.  Take a look around. 

[Chevrolet1]

Some forum members have posted about transmission & shifting concerns in the general section (instead of the engine / driveline / exhaust section). One of those is below and has a lot of info. And a search on this site will bring up multiple other posts as well.

 

Info:

Occasional harsh downshifts during deceleration = TSB 19-NA-244. Resolution is reprogram the TCM.

Shake / shudder during light acceleration = TSB 19-NA-121. Resolution is to flush fluid and install latest high perf. fluid.

 

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Edited August 22, 2021 by Chevrolet1