Got an oddity occurring with my 60E. Occasionally when launching from a stop the trans will be stuck in 2nd gear for a few seconds and then bump down to 1st. This only occurs in the D selection. 3rd selection launches in 1st and works up normally as far as I have seen. 2nd selection launches in 2nd and stays that way, going WOT results in what feels like an attempted downshift and transmission shudder. 1st selection launches in 1st normally and upshifts before the limiter.

The trans does have WOT slippage on the 2-3 shift. The 2nd gear launch problem has existed before the slipping problem, though. Could this be something easy to fix that doesn't involve a complete rebuild?

 

when did this start? after a rebuild? tune? or just out of nowhere?

from my understanding 1st gear is both solenoids "on" second turns off one solenoid...I might suspect a weak solenoid or sticky valve for that solenoid....

I do know both solenoids are easily replaced from dropping the pan...they are both beside eash other and look identicle...

But before you go spending money on parts maybe hook up a diagnostic scanner to see if the computer is even commanding 1st gear during the issue you described

 

My Avalanche sometimes starts on in 2nd gear, has done that since about 65k miles, currently has 202k and never has been rebuilt. There is a TSB out there that puts blame on the ignition switch for the 2nd gear start.

On my Suburban there was NASTY slip from 1-2 and 2-3 but that was solved by maxing out the shift firmness on the tune. The tune happened at 173k and still rolling at 222K so it bought some extra time for sure.

 

its inevitable... start saving for a rebuild or an 80e swap....

 

Started after a rebuild and got worse when I upped the pressure in the tune to gm's max specs.

 

My stock tranny also sometimes sticks in 2nd gear, and has really sloppy 1-2nd shifts at mild throttle. Already looking into the T56 swap.

 

Do you have your own software?

make sure the main elec. connection for the transmission is clean and tight...If it becomes loose or poor connections are there, it may cause problems, easy check.

If you can, scan it and watch what gears are being commanded, this should help point you in the right area possibly

 

My truck has started in second from time to time since the truck was almost new
My brothers 05 does it sometimes aswell, both original transmissions