Hi folks, I'm trying to trouble shoot an issue with my '99 Wrangler 4L Auto with 105k mi, where shifting into drive after vehicle has sat for a day or two results in very little movement until after 3-5 seconds. Almost as if the vehicle is in neutral until it builds enough pressure and starts to creep forward. Once warmed up the issue will disappear for the rest of the day, even if it sits for a few hours. It definitely seems more pronounced with the temps falling here in CT.
I have drained the ATF twice in the last 6 months of ownership, once to perform routine maintenance and the second to adjust the bands (the issue was already present). Each time I replaced the filter and refilled with ATF +4. The fluid levels are ok according to the dipstick.
Probably unrelated, I get a transmission whine in first gear when taking off. I read that it might be the planetary gears but regardless, it doesn't seem to affect the shifts which are smooth across the board.
Somewhere I saw it may be a failing check valve on the oil cooler supply line and to check for that I should shift into Neutral for 10 seconds and then to drive to see if that solves it. Maybe also a pump issue. Thanks for any suggestions.
PS- any ideas on rebuild costs? Would that fix the trans whine when starting out?