P0758 immediately after tranny fluid/filter change,

[mike2004tct]

Dropped the pan, replaced the filter, and added 5 quarts of Castrol DEX/MERC fluid (2005 and prior GM trannys).

Started it up, backed off the ramps, went forward, and very sluggish start.
Code popped up almost immediately once going forward.
Erased it, went forward, and code came up again.
Truck seems to be stuck in 3rd gear. High RPMs on take-off.

I know I didn't disturb any solenoids, or pull any wires.


If I put the gear selector in 1st, truck takes off as normal.
I'll have to test drive it awhile and see if this will pop a code too.

What's going on?

[MT-2500]

Code 758 is for 2-3 shift solenoid electrical problem.

Drop the pan and make sure the wiring plugin on it did not come unpluged or break off.

Very easy to knock off the plugin when removing or installing the transmissionn pan.
Sometimes it helps to slide cross member back for more room removing and installing oil pan.

Let us know what you find.

[mike2004tct]

Originally Posted by MT-2500

Code 758 is for 2-3 shift solenoid electrical problem.

Drop the pan and make sure the wiring plugin on it did not come unpluged or break off.

Very easy to knock off the plugin when removing or installing the transmissionn pan.
Sometimes it helps to slide cross member back for more room removing and installing oil pan.

Let us know what you find.

Well, I should have removed the cross member to begin. All I did was disconnect the 2 bolts at the tail shaft mtg bracket to the cross member, and jacked the tranny up to get the pan out.

Bonehead of the Moment award to me.

I dropped the pan, and the solenoid on the passenger side rear of tranny was broke. There's 2 of them, side by side.

Apparently, I banged one putting the pan back up, dislodged the plastic connector housing from the assembly, and broke the wires off the coil of the solenoid.

Went to a Chevy dealer this morning and bought a new unit, put it in, truck now runs fine, overdrive and all.

$45.00 part/fluid, plus 2 hours mistake.

[MT-2500]

Thanks for posting back how it went.
If it helps that happens to a lot of people.
I unpluged one solenoid wire one time.

Good luck