In the new TJ's, I have had Jeep mechanics tell me that with an auto, the easiest way to shift into 4-Low is with the vehicle in Neutral AND turned off. (found this out after I destroyed the linkage on a 3 DAY old Jeep
. Turns out they had forgotten a bushing at the transfer case... Gotta love Jeeps!
) I am not sure if this is useful in the YJ's also, but you might as well try, will be a lot cheaper than any other fix!