Mercury Cougar Owners banner

highway RPM and mileage estimate

2410 Views 11 Replies 6 Participants Last post by  Cougrrcj
Anybody running 400 HP, C4 with shift kit with a 9 inch equalock rear and 3.55 gears? I'm getting ready to gut my cat and I think I might go with this combo. This is somewhat my daily driver so I'm trying to find a good combination of daily driving and Sunday night racing...

I heard AOD will help with highway driving, but there weak is their any truth to that?
1 - 12 of 12 Posts
How much of your commute is highway? AOD will spin about 30% slower in high gear so you can expect about 30% fuel savings but obviously only in high. Does also save some wear and tear at speed. In any case you would want whatever box you put in there built to handle your racing activities.
I remember that my original stock J code with a 3.00 rear only averaged 13 mpg back in 1970 on premium.
Cleveland in that power range with that trans and gears got 17 on the highway. But, that's a Cleveland. You don't even need a hot cam for that.
I've got a ~400hp 393W, AOD and 3.55 gears. Still get a shade less than 15mpg rural/city. Not really city and not totally highway. In fact, I haven't gone a whole tankful of straight highway driving. With my 225/70/15s being 27" tall, the engine is turning around 1850 in o/d at 60, or 2650rpm in Drive.

Oh, and here's my car at the starting line... with an AOD. Any questions? Yes, it is a wide-ratio AOD (4R70W gearset in an AOD), with a 2500 stall converter w/ lockup. And Yes, it does have the hardened inner input shaft. This is a 4150-pound car running 13.20 @ 105. Your lighter cat should do much better!

See less See more
AWESOME!! What year cougar is that? Where or how can I get the parts for an AOD to do the things I want with it. Right now I have a C4 with a shift kit and that thing is bulletproof. It's gone through a lot of tires but kills me on the freeway. 400 horses is not a lot if you don't feel it at the wheels. My C4 is starting to slip, so I was thinking of going to AOD with 3.55.
AWESOME!! What year cougar is that?
Funny guy! That's my '89 Crown Vic...

You can get a AOD with all of the goodies already in it like mine for around $1800 the last time I checked. Mine is similar to this. Mine was built by a buddy for much less using a couple of the proper year junkyard cores - 90-92 AOD and 98-2002 4R70W.

Initally I was using a Baumann ( shift kit, but over the winter I picked up the Silverfox SPT-R valvebody with 'stage 3' calibration. Silverfox ( will custom-tune the valvebody to your specific application. The SPT-R gives a 'normal' 1-2-3 shift pattern and has an electronic OD switch. Otherwise the AOD requires you to do the '2-D-2 shuffle' to manually shift through the gears...

The limiting factor in an AOD is the inner input shaft if you want to retain torque converter lockup in D and OD (which I wanted for gas mileage). It is only around 5/8" diameter. It can only withstand about 450 lb/ft torque. The aftermarket hardened shaft can take around 550 lb/ft. I got mine from Broader Performance.
See less See more
just tugging your leg man haha. thx 4 the info. I like that website.
Anyway, you can also use a 4R70W from behind a 4.2 V-6 (same bellhousing pattern as SBF) and use a stand-alone controller. The 4R70W can handle up to 700 lb/ft torque!
I'm getting about 18 w/ AOD and 3.55's and 14" wheels. (Holley 750) She's still on the rich side though - I bet I can get it to 19 or 20 with a little better tuning still.....I have to do the 2-D-2 shuffle, but I really wish I had the SF valve body! I should look into that.....but to many other things eating my wallet right now.
What do you mean 2-d-2 shuffle? Is that when you get on the freeway you drop it into OD? and on the street its just the regular D?
With a 'normal' AOD valve body, there are only three gear positions on the shifter, yet four gears counting Overdrive. The Selector is P-R-N-OD-D-2. Normally that isn't a problem. The AOD will shift itself at WOT 1-2 at 4500rpm, and 2-3 at 4200rpm. The 'high speed governor' in a Mustang will shift about 300rpm higher. To manually control the shift at higher-than-normal RPMs, you start with the gear selector in the lowest position (usually marked '2') to manually hold it in First, then when you reach the RPMs you want to shift you briefly move the shifter to 'D' then immediately pull it back down into '2' for Second gear. Then when you reach the RPMs you want to shift again, you move the selector into 'D' for Third (or Drive). My 393Ws best ETs are found by shifting around 5500rpm. If I leave it in D, the car will shift itself at 4500/4200 and it runs a full second slower.

Anyway, the Silverfox SPT-series valvebody is custom-calibrated to shift at the RPMs you specify when ordering. It is adjustable with a setscrew to -200 and +600 of the 'customer-specified' shift point so you can tweak it a bit. I went with the SPT-R that allows the normal 1-2-3 shift pattern (without the 2-D-2 shuffle) and OD is an electronic button.
See less See more
1 - 12 of 12 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.