Car: 1966 Chrysler 300 383/4bbl all original w/ 120k miles on it.

I had a leak in my transmission pan gasket and the fluid level dropped to somewhere below the dipstick during a long highway roadtrip ( I was on the throttle hard for most of the way)

Went to drive it today and it was incredibly slow to shift into D, and would spin the engine w/ no forward motion. Checked the dipstick, and after tightening the trans pan bolts, filled the level back up to normal. The fluid on the dipstick is an icky brown color - now the trans will slowly shift into D but is slipping badly, and will just spin if I give it any power at all. Upshifts are not noticeable at all, and it won't take any power at all. Before yesterday upshifts were nice and firm and timely.

Could I have damaged the trans or do you guys think I can just change out the fluid and carry on?

I was thinking I could disconnect the trans cooler line at the radiator and let it idle in N while it drains into a pan and I pour fresh fluid in through the dipstick tube?

I'd pull the pan & see if the filter looks plugged

Nothing in the pan, won't have a replacement filter for a few more days - has anyone here used Trans X treatment before?

Don't add any trans fix in a can to your trans unless you are prepared to rebuild it tomorrow. Pure crap and does more harm than good.

how should the bands be adjusted?

Changed out fluid and a little better but still very sloppy shifting. How do I correctly adjust the bands?

The front band, depending on what the factory service manuals calls for is to loosen the lock nut on the front band and tighten the adjuster,it is external (while holdiing the lock nut) to 72 inch lbs and then back the adjuster bolt off from 1.5 to 2.0 full turns and lock it down, Google the specs for your year tranny and motor size The rear band is harder to get to, you have to drop the tranny pan

Check the t.v lingage at the carb and make sure the spring is still hooked to the carb.
When that breaks and falls of it will do some of the same problems your talking about.

Update - I replaced all the fluid and filter, linkages are good, adjusted the front band and still the same problem. If I just barely give it any throttle, it shifts from 1-2 and 2-3 with a noticeable shift... if I give it any power at all it just slips.

Was the old fluid black and smell burnt?

It was more brown and yes it smelled burnt. The old filter had specks of metallic particles in it and there was a solid layer of grey sludge in the bottom of the pan.

Sounds to me like it is done. Time for a rebuild.

You have no rear clutch left for sure......it's gotta come out.

Bummer - thanks for the input

I used TransFusion if you can find it.Ive used it at home and the shop for 30 years.Its one additive that works.It wont fix an internal problem but Ive used it in some fairly bad trannys and it did wonders.Change the fluid and filter and add a quart.If no major problems it will help.Rocky

If it shifts real quick as you say you should make sure the throttle press rod is set right. That will cause fast shifts if to low and can cause the trans to slip as it also acts on line pressure. Even if its wasted you want to get the throttle pressure right so you dont mess up a rebuilt trans. Ron

What is the proper way to adjust that rod?