My 2000 GC Limited has been down due to some cooling system issues since October of 2024, just about a year. I have now resolved those issues and went to start and drive it, But when i Placed it into reverse it didn't go into gear, Same thing when putting it into drive. When putting it back into Park there was a little bit of what sounded like flywheel or gear grinding very briefly and then it stopped. I topped off the trans fluid but that didn't change anything. What components would be affected after sitting for almost a year that would cause this ? When I parked it last October, I had not been having any transmission issues whatsoever, It's always been very solid.

Hoping it's something simple....lol

 

I checked for Codes with Innova 5610 scanner, No Transmission codes were shown.

 

Stuck torque converter or the front pump lost its prime from sitting. Try this: start it in neutral, then shift to drive. If that doesn't work, check the linkage first to make sure it's actually engaging. If it's still a no-go, the pump might be dry; you might need to pressure-fill the cooler lines to get fluid moving. Sitting that long is rough on an auto box.

 

Tried Starting in Neutral and shifting to Drive, No change. Checked fluid level, was full. Checked codes again but nothing recorded. Not sure how to pressure-fill the lines. probably should take to Friends shop, He has Auto repair business and is always busy, But maybe he'll squeeze me in. Have never had an issue with this trans. but i understand what you said about sitting for long periods.
Thanks for your ideas...

 

I hate mysteries, but I love to apply the old K.I.S.S. principle. And all this transmission shifting without appearing to engage in gear or move at all leads me to wonder if your Transfer Case (T/C) is somehow set in Neutral or is something is disengaged. Try running through the T/C settings with your service brake set (else brick-block a wheel fore/aft), leaving the T/C it in 4WD-Low, with your engine running, and your transmission in Neutral. Then, while idling, with foot on brake, set your transmission in any gear (again being gentle to the drive-line for now and not throttling). You should see, feel and/or hear something, and then you can take it from there, trying all selections including T/C "N" selection again. Just remember to restore your T/C selector to 2WD (following procedure) before taking your Jeep out on the pavement. Try this and LMK what happened, okay?