2005 4L60E 2-3 clunk

I have a 2005 Avalanche with the 4L60E, and have added Corvette servos.

I have the infamous driveline clunk under very light throttle during the 2-3 upshift. It was there before & after the servos. At higher throttle, it shifts perfectly in all gears.

I have tried adjusting the following without much luck
* lowering pressures at low torque
* raising and lowering shift speeds
* torque management on and off
* lowering 2-3 shift pressure multiplier at low torque
* shift timing as quick as 0.2 sec up to stock at low torque

Any thoughts on how to tune this out?

Thanks

Has the transmission ever been overhauled? If so it seems like someone may have left out the springs that go in the input housing around the 3-4 clutches. Or you could have the infamous slip yoke clunk, but that usually only happens on take-offs. Doesn't really sound tuning related if you ask me.

The trans has never been overhauled, and it has done this since new. The clunk is not really that serious, and the dealer didn't think it was anything either. However, I am quite picky and now that I have HPTuners, I would like to see if I could fix it with some tuning.

Anyhow, the clunk only happens during the 2-3 upshift and only if <20% throttle, but does not happen from start. The resulting clunk does sound like it causes slack in the driveshaft which then translates to the transfer case or diff.

Also, I gather this is not that unusual in similar vehicles (1500 series SUV, & pickups with this trans)

I have seen a TSB for the noise you describe.
The TSB stated that this is not a "fault" and should not be claimed under warranty.
The reason was that during the shift event, the servo/s are pressurized in anticipation of the shift.... any how this lead to a moment of "negative Tq" being transmitted from the rear axle in to the transmission.

If you can tune it out, at least I want to know, please:worship: my hoe does it as well.

//

Yeah, GM "attempted" to tune it out in the 05 4L60E trucks and had some trans issues because of it... Hmmm... I'll keep the clunk thank you.

Hi, I just wake up this thread, this 2-3 clunk boring me, after 10 years anybody find how to softenig this shift?

An accumulation of tolerances in the transmission, transfer case, and rear differential. Everything needs some amount of backlash or play. Usually happens when you are coasting down as the drive side of everything becomes the driven. I don't think there is anything you can do about it.