I have a 1992 gmc safari and the transmission wont shift into 2nd unless you manualy shift it and then wont shift into 3rd

Not a wire. Your transmission shift cable may be disconnected from the throttle. Or if you have a vacuum modulator the vacuum tube may be disconnected. Check your fluid level.

change trans oil and new filter if problem still there it most lickely the shift modual

Seals. Try some transmission seal conditioner. Tranx is good. Mine took a couple of days to clear up.

sorry tosay sounds like u need a transmission

Sounds like your transmission is in limp mode. This is a fault mode in which the transmission either loses electrical power or the PCM deactivates all of the electronics. The transmission will default to max line pressure. The driver will have Reverse and 3rd, with manual 2nd available by putting the gearshift in 2 or 1 (doesn't matter). 1st, 4th, and TCC lockup will not be available. It will not hurt the car to drive it like this for short periods, but use manual 2nd to get the car moving, and be aware that the trans will generate more heat than normal while operating in limp-home mode due to increased torque converter slippage during 2nd gear starts and no lockup in 3rd gear.

The other from what you described, trans shifts 2nd to 3rd by itself in D or OD and locks the converter : ShiftA solenoid failed. Easy fix in the pan. Or a wiring problem from PCM to trans.. or PCM.

Thank you for using fixya and have your Safari scanned for the DTC codes that would indicate what issues your transmission is having to put you in to limp mode.

could be the switch on the trans or the pump may have went out, or something is wrong with the valve body inside the trans

3RD & 4th shift solenoid is bad inside the transmission

Wow, never heard oof this happening. Yes on the sensors , reverse lights, neutral safety switch, and shift speed . Good luck.

what that means is that you have a solenoid in the transmission that is either sticking or is no longer any good. you don't have to replace the wholetransmission but need a replacement solenoid/and or pump.

Check that the OD solenoid on the torque converter is good still. When the R4 wont go into OD you have no more gears than 1st an 2nd. If the OD clutch drum was relaced if it was burnt, that will make a problem also. You have to have OD in order for these babies to work right.