with a 3 speed or 4 speed without overdrive, be it manual or automatic, the top gear cruise rpm will be the same, as they are all 1:1 ratio when they are not an overdrive.

AOD is an overdrive, so it can take a bit more gear out back and not have the RPM hangin around 4000 or so doin 75 mph on I-80 through the lonely stretches of Nebraska or Nevada..

Simple way to find out approximately what RPM you will be turning at a given speed with a certain tire and rear gear is this.
Using math here so if you need someone to explain it, that can happen.. dont feel bad if you dont get it.

(rear gear x 336 x trans ratio) / (tire diameter x rpm) = MPH
or..
(4.10 x 336 x .72 ) = 991.872 or rounded 992
(26 x 4000 rpm) = 104000

Divide 104000 with 992 and you get 104.8 mph.. provided there is no slippage in the drivetrain.

Now the .72 is the overdrive ratio, lets see what happens when we use a 1:1 gear in the trans, like a 3 or 4 speed..

(4.11 x 336 x 1) = 1380.96 or 1381
(26" tire x 4000 rpm) = 104000

divide and it equals... 75.30 mph

So then the OD in an AOD is worth almost 30mph in extra cruise speed for that RPM.

(3.0 x336) = 1008
(26 x 2000) = 52000
= 51.58 mph cruise MPH
(3.55 x 336) = 1192
(26 x 2000) = 52000
= 43.62 mph

So the difference at 2000 rpm between a 3.00 gear and a 3.55 gear is 8.38mph

336 is a constant sorta like Pi, you know 3.14..

 

Ah Thumpin, go put some used tires on top of your trailer house, and put out some plastic pink Flamingoes in you front yard. Nobody has that kind of space to keep old pumpkins like you do.

 

I got the idea from my dad, who has 5 old fridges in the qunoset where the Cougar was stored for 20 years. The only people I know who dont have space are the sheeple who live in city limits with a neighbors house 15 feet or less away, and the poor college kids who live in dorms and apartments. the rest are not car types so they dont need storage space.