All AOD equipped SC's had 3.27 gears and 225/60/16 tires. 4th gear in an AOD is 0.67:1, so 55mph in OD with 3.27s would be just over 1500rpm. 3.08s would be about 1450rpm, and 2.73s would be about 1300rpm.
I have 2.73s on my car and it really kills the acceleration. I'm thinking about going with the 3.27 to increase 0 to 60, but I also want the good mpg. Also, i dont have a super coupe, I have the 5.0. The reason I'm asking is because it's the "best" thing to compare it to ?
I think this is a trick question because who would actually drive 55?
They put 2.73's in V8 T-Birds for years, pretty much all years in the 70's and 80's. In the 60's they used 2.75's with the 429's. Talk about a waste of big block power.
I am curious which year the OP has, and if he actually has 2.73's. If it's an 88 or older, definitely!
Not a trick question. I own a 91 5.0 and I'm using it for daily driving. The roads I'm getting on are 55 mph. The 5.0s in 1991 were equipped with either a 2.73 or a 3.08
That’s not true. Unless you or someone before you changed the rear gears, you have either 3.08s or 3.27s. The only MN12s that came factory with 2.73s were the 5-speed SCs. The fox body cars could be had with the AOD and 2.73s, but they also had shorter tires, and were at least 400lbs lighter.
This is incorrect -I have a 91 Cougar LS, 5.0HO, stock 2.73 rears switched to 3.73's about a 1 second improvement in 1/4 mile times, LOL. 5000RPM shift out of first was at 60 mph or so:grin2:
I'm about an hour away from the car unfortunately. I'll look at the tag when I get a chance. Was under 1400 rpm at 55, just over 1600 at 70. I worked at a Ford dealership during college when I did the gear swap. Discussing options with the Ford tech we decided to find a junkyard rear with the trac-lok to build while I was still driving the car with the 2.73 open diff. I've been mistaken before but don't think I am here....
It could be that the junkyard diff you got had 2.73s, since all the early SCs got a trak-lok, and nobody wanted the 2.73s so they were always cheaper than the 3.27 ones out of the autos. The door tag will tell for sure what was originally in there though.
I'd get 27-28 mpg on 2 Lane roads going 62 in a 55mph. 72 on the freeway around 24, if I remember correctly. Switched to 3.73s 13 years ago. Been in the garage most of those years after trans went out.
I recently switched to 3.73 from my stock 3.08 5.0 lx and mpg went from 24.5 mpg at 74 mph to maybe 21 or 22 (any long drive involves hills in my area). I don't do long trips with it since doing mods but it was a 21% gear reduction using my math:grin2: so a fuel economy reduction is expected/guaranteed when you are in high gear and past about 1500 rpm.
As far as 0-60mph went for me. I switched to 3.73's in part to improve the time since it had to shift to second before it would hit 60mph. I remember not being able to hit 60 mph in first without hitting the 5000 rpm red line and I won't try it now with 3.73's. My tach does have a 500 rpm echo or something that can't really be trusted at high or WOT. Nobody has offered to time me so 0-60 is still a mystery.
Put an acceleration app on your phone, and you can see the shifts.
Should be able to see the timing as well.
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