I have a 4 speed auto in my 4.0L that pops out of gear when trans is cold. If shifts great when warmed up. It starts out ok in drive then just revs. If you stop and push the gas hard, it jumps back in gear. Changed fluid and filter, same result. Neutral safety switch going bad?
It sounds to me like a tranny that's a little low on fluid. It's does have a lot of miles though, it could just be on it's last leg. I don't know how many miles a Jeep with an automatic usually gets. A little more than a quart & 1/2 low & mine will lose fluid pressure on hills and trailer ramps etc. Just my two cents.
I found out that my tranny needed to be rebuilt 2 months after I bought it at 67,000 miles.
That was not a lot of miles for a rebuild (I am getting scared). My dipstick reads a little over the hot or cold mark sitting on level ground. I wondered if it had too much fluid so I drained a little, and get the same results.
How are you measuring the level? It will give you a different reading with the engine on vs. off, and in park vs. neutral. I believe the 42rle needs to be in park with the engine running (and fully warmed up, drive around the block a few times) for an accurate read.
I'd replace the fluids and put a new filter kit in it just to be safe but it does sound a little low on fluid.
03 Rubicon a.k.a "RubiX", 35x12.50 MT MTZ, 4" lift and all the other fun stuff Rubicons come stock with such as front/rear lockers, Dana 44s, T-MAX 9000lb winch, and much more to come.
Gone but not forgotten: 98 TJ; 4.5 lift, 33x12.50 Pro Comp MT, and lots more.
I put a authentic hand grenade on my stick so I had to do away with the neutral safety switch and my transmission doesn't pop out of gear so of say the neutral safety switch is not your problem. If its a cold/warm issue I too would say its time to change the fluid and filter. And like the other guy said, warm the transmission then park on level ground, wheels chocked and transmission in neutral, the pull the dip stick and check the level of the fluid.
Yea, that's what I was thinking also, my truck has 215,000 miles on the original tranny. The strange part was, it was driving OK at least that's what I thought it was. When the pan was removed it was full of sludge & metal shavings.