Moe in Wichita, KS mopar auto trans
I am not a trans expert. This is just what I have learned about mopar trans over the last 40 years

On the older mopars the Trans would not go in reverse when the Trans oil filter was clogged, cold weather made this worse. Why rev. and not forward gears? Because rev. runs the trans. line pressure to 350 psi. forward gears to 100 200 psi. the higher pressure takes more volume of oil that the clogged filter can’t pass. but I don’t know about the newer trans. Also the older trans stops the lube/ cooler line in park so in hot weather don’t sit idling in park. It will over heat and spit oil out the fill tube. And on some cars gets on the ext. pipe and cause a fire. If your older mopar trans bangs real hard going straight to rev. try going to low with the lever, then go rev. it wont bang as hard, remember the pressures? If you look at the trans flow charts you will see that the low/ rev band is on in low gear only if the lever is in low, in drive low gear, they actually call it breakaway, the band is not on, it is always on in rev. But it really needs a low/rev band adj. A trick to get longer life is to put rear end grease in a trans, one or two qts. Two works good in 727s. It will shift better to. I have used this trick on the older trans, 727, 904s with no bad effects. This may or may not work on newer trans. I have put one qt in my 99 Dakota v 6. about 8 mo ago, so far so good. A cooler is ALWAYS a good idea. I have had shift kits in two trans, I think they are good. Just don’t do full race kit on a street trans. If you have a 7 ¼ dia. ring gear rear end don’t make it shift hard going from 1st to 2nd, it will break the spider gears over time. I understand the newer trans have a check valve in the cooler lines. So if one of these trans blows up the check valve will hold junk and keep the fluid from lubing the trans. So the valve needs cleaned after a blowup. Don’t forget these trans have an aluminum case, use anti-seize compound on the bolts and don’t over tighten the bolts.