Hard 1-2 shift

[kaseynhl]

Has anybody heard of a bad alternator/low voltage problems causing
hard 1-2 gear shifting?
1997 K1500 4 wheel drive 350 motor.

Thx Kasey

[akz71]

No I havn't heard that one yet. I have a 97 k1500 w/same problem. Found out some info that the valve body in the trans. is crap, and recommended fix was to install a sonnex valve kit tcc regulator w/sleeve to cure the hard shifting

[2000CAYukon]

Low voltages to the tranny (usually caused by a bad ignition switch) can cause the tranny to go into "limp mode". Line pressure is increased and it will result in a very firm 1-2 shift. So yes, low voltage can cause a hard 1-2 shift.

However, as akz71 pointed out, a bad tcc regulator valve/worn bore can also put the tranny into limp mode. A P1870 is usually set at the same time.

You should get the pcm scanned for any codes. The voltage can also be tested at the harness to verify if the ignition switch is at fault (assuming the electrical system is functioning properly).

//2000CAYukon

[wardriver]

This fixed my exact same situation.

If you are not using your cruise control, then turn it off at the switch.

Your issue should subside.

Let us know if that works.