1997 GMC Jimmy Tranny Problems

Those transmissions have a somewhat notorious problem with an internal piece called a sun shield. It explodes & turns into metallic sand & ruins the transmission. Pull your dipstick visually inspect the fluid on the end of the stick, and clean the end of the stick with your fingers and feel it. If your sun shield has terrorized your tranny, you'll be able to tell.

If the fluid on the stick looks & feels clean, see if your problem is just that the transmission isn't automatically shifting any more. At a stop, place it in 1st gear. Start out, run it up to 2,500 RPM & shift into 2nd, then up to 2,500 RPM again & shift into 3rd, and then at 2,500 RPM again, shift into overdrive. You will be able to feel what gears it's shifting from & to.

I recently had a problem where I only had 2nd & 3rd gears (had to shift manually - even with selector in 1st I was starting out in 2nd), and my ignition switch wouldn't let me remove the key when I turned it off. There is a selenoid at the ignition switch that lets you turn the key all the way back, and if that selenoid isn't activating, there is a small hole in the bottom of the steering column right under the ignition switch, you can poke something skinny up through that hole & push the rod of that selenoid up & will allow you to turn the key back & remove it.

My problem magically healed itself recently. The key is removable normally again, and the transmission is shifting through the gears as it should. I've posted on the forum fishing for info about where the electrical connections are for this circuit, as I'll probably be revisited by that problem again someday.

Replace ignition switch $40 and splice in wires instead of tearing under dash apart. For some reason the switch tells the computer to go into limp mode which makes it stick in 3rd. Pretty easy if you're handy.