I've an old A/T w/ low mileage, but has been sitting for many years. Is there any additive or snake oil anyone recommends to help ensure it's smooth operation when I fire it up again, or is just a fluid and filter change the best way to go?

Just new fluid and filter. No snake oil.

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Joshua

I would recommend replacing the fluid and filter, but while you are in there doing a couple of free modifications:

(1) Remove the accumulator spring
(2) Adjust the line pressure screw as far out as it will go without falling out of its holder
(3) adjust the bands

I did these modifications to a 1974 727 that I got for free from Eric W who got it from a junkyard. THe transmission had been sitting in Brett's garage for a few years so I would guess that its condition is comparable to your transmission. I installed the tranny in my brother's van and it has worked flawlessly for over a year now. It shifts nice and firm too.

Lucas makes an ATF additive, but that would be the only one I would try.

Might I suggest new front seal? If its "on the ground" easier to replace it now

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83 B-150 slant 6,4 speed. 79 B-300 360 pathfinder 4x4. 74 W-300 318 4x4 git-r-done 80 B-100 sl6,4speed

Second the front seal suggestion.

Increasing the line pressure slightly is OK. Backing the adjustor out until it's just shy of falling out is unwise to say the least, unless what you're trying to cause is improper shifting and early seal failure.

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Interesting. I just followed the recommendations of several Mopar Magazines. It has worked fine for my brother for over a year now.

Several Mopar mags, also recommend replacing the slant six, with a V-8, under all conditions, also.

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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Thanks again for the good advice.

The trans isn't out (or I would replace the seal) and to the best of my knowledge used to run just fine and not leak, so I think I'll just change the fluid and filter, start it up, treat it very gently for awhile and hope for the best without changing anything else, just to keep it simple for now.

I have tried the Lucas stuff in another (Ford AOD) trans that had a little shudder and it may have helped and didn't seem to hurt, but I really can't say one way or the other for sure.

Yeah, but I'm not that dumb. The accumulator spring was actually already removed when i got the tranny so all I did was a band adjustment and increased the line pressure. No bad side effects yet. I will keep my fingers crossed. No leaks, shifting is fine.