Shooting for 30 mpg with my '92 Mark VII.

[The_Jed]

I took it for a drive and it seemed to have more wnd noise at the side mirrors and windshield. I'll do some back to back tests with it installed and uninstalled when I get the chance to see if the noise was all in my head.

[cosmick]

I hope you take this as helpful rather than contentious, but calculations mean nothing. The AOD is notorious for incomplete lockup, especially in third. The reason diff covers never came with drain plugs is so you'd have to pop the cover and visually inspect everything, which is a fine way to confirm the tooth counts stamped into the perimeter of the ring gear. Many people never change the diff lube, yet get away with it for decades and several hundred thousand miles. But the cover gasket is $3, and 2 quarts of synthetic 75W90 are $8, so there's really no excuse for not knowing what's in there. And even if there is a magnet in there, it likely needs cleaned off. Plus your Traction-Lock diff probably needs rebuilt, so this makes it easy to confirm. Ford offers new clutches for it at maybe $35-ish.
Or get the complete rear assembly from a '94-'98 'stang GT auto with the 2.73:1 already loaded and set up correctly for no whine, then do the above to that before swapping it in. That's under $ 200 all total. The glitch is that the 'stangs that came with 2.73:1 used a different output shaft in their AODs, with more teeth, than 'stangs with 3.27:1, so you'll need a little correction box, those are $62 from PATC.

[The_Jed]

I disagree about calculations being meaningless but agree about the diff oil. Also, if the diff tag has any credible info on it at all, mine was a peg leg from day one. I've already put my feelers out for a diff on grm.

[The_Jed]

Hit the highway today with my makeshift air dam and while hitting 70 mph took very little throttle before, it seemed a tad easier, nearly effortless. Even though I'd hardly call it empirical data, the instant mpg readout on my tripminder read 1-2 mpg higher than it usually does along that particular stretch of highway and my average mpg over the past 600 miles went up by .2 mpg so it's safe to say my car likes it!

The front of the car also felt more planted at speed.

[67-ls1]

Got any pics of the new air dam?

[The_Jed]

Oh, it's ugly. I haven't taken any pics of it yet.
I'll see about getting some tomorrow.

[The_Jed]

Using a formula found on this site it looks like 2,000 rpm would yield 1,000 ft/min piston speed, which I gather is the low end of the sweet spot.

With 225/60 tires and the 4r70 gear set that would put me at about 63 mph.

With the same tires and the aod gears I'd be at around 66 mph.

With 4r70 gears and a 2.73 ring and pinion that would be almost 83 mph.

I'm sure it's just another bit of data to be taken into account when trying to dial in the best compromises in all aspects of f.e. for an ecomod set up and not THE deciding factor but that seems to indicate the 3.55's may not be so bad after all.

[The_Jed]

[The_Jed]

[The_Jed]