What kind of fluid should I use to top the tranny in my stock 72 Dart /6 car? Is +3 or +4 recommended or can I add synthetic? My Haynes manual omits the 72 year model.

Run any good Dexron II or run Type F if you want solid, barky shifts. I doubt +3 or +4 will hurt, but it's really formulated to be an improved fluid for lock up transmixers, which you do not have (stock). I'd probably just run regular ole' Dexron...

"DW"

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If it ain't broke, fix it!

Sounds good DW, I'll top off with some Dexron.

+3 and +4 have friction modifiers in them to improve shifting in the new AOD transmissions. Some guys have used +3 in their 727 with no problems, but lots have had 'slippage'. (Similar to using sure grip oil in a manual tranny).

The older A-727's used to use Type-A (later type F or even FA), there have been lots of articles about using it for 'hard shifting' in the later trannies, I also have heard it sticks the bands to the drums a bit longer causing 'harder shifting'(hard releasing) and also stress on the components.

I've never had a problem using Dexron/Mercon 3 in any of my post-66 A-904's or 727's, there was a brief article in Mopar Action that described how to adjust your tranny for more positive shifting, forget what issue it was...

-D.Idiot