Technical 8 inch rear end ratio for use with 302/AOD in '54 Ranch Wagon

I'm putting a stock 2 barrel 302 with AOD in my '54 Ranch Wagon. I'm using a Maverick 8 inch rear end. It has a 2.80 ratio right now which is way too tall. Trying to decide between 3.55 or 3.80 gears. Planning on 215 15's/27 inch diameter tires. My approximate calc's for 65 MPH are 2150 RPM's with the 3.8's and 1980 RPM's with the 3.55 or there about. Any thoughts on which ratio? As always thanks for any advice.

 

I run 3.6's in the Big Bearing 9" that is in my '62 Monterey behind a 352FE / AOD combo with much larger 30" tires. It works great, but I guarantee my FE also has much more torque and grunt below 2500 rpms than your 302. Cruising at 70 mph is around 2100 rpms with the lock-out feature removed from the AOD.

Alot is going to depend on the torque curve of the motor. But a 302 is generally a short stroke, high winding motor so you will want a bit more rear gear.

 

3.55 is the closest to that. Next is 3.80. Th e8" has limited gear ratio selection compared to the 9"

 

Just an FYI, my OT '93 Mustang has a 5.0/AOD and the rear gear is 3.27 from the factory.

 

I have a 300 gear under the '54 Ranch Wagon and a 5 speed manual transmission, I'm using a mid 60's Mustang rear axle. HRP

 

My Tbird is the same set up 2000 rpm is about 70 mph

 

Unless you do a lot of towing, I would think that you would be happy with the 3.55 ratio.

 

The factory's spend a lot of time,to pick out best rear for a combo,the same combos you need to use=What are you going to use car for the most* How many lbs is car or truck,and load in it most.*How much power it has* Were is it being used* Some of that above is out the window if racing only!
Getting back too point;
Looking at rear ends gear# of a factory car or truck that meets close to same things your planning on putting together,will give you a gear number best engineered for that combo< Factory's pay a lot for engineers to get more right then you or I can guess it///Am I am a engineer an made my living designing,building an racing cars for 40 years.

 

3.55 and maybe even a 3.30 Going from 2.80 to 3.80 is a really big change.....

 

I am not there yet, but planning on 3:80’s for my 302/AOD in my 56. Look at the reviews for this set at Summit. Seems like 3:73 was about perfect but somewhat harder to find and therefore more expensive.

 

Our wagon is not a powerhouse coming of the line but it sure good on the highway. HRP

 

not easy to find complete low ratio 3rd members for

- complete 3rd member hard to find used, new gear sets expensive new - 3:55 worked for me

 

i had 3:80 with 235 tires, ran 2100ish at 70

 

I had a new 3.55 gear set in the 8 inch in my 40 coupe with a none od trans and it was to deep I replaced it with a 2.80 and it's now a good road car. I now have a 1300 mile 3.55 gear set to get rid of?

 

I can find both 3.55 and 3.80 gear sets new for about the same price. 3.80's are a bit more $$ but not all that much. Not going to do any towing so the 3.55's should work. Not a whole lot of room for a larger tire. I'm picking up the rear end later today. Next is to do some checking on someone to set up the third member.

 

I had a '90 "7up" car with the same combo, 3.27 was the optional gear with the auto - I swapped them out for 4.10s - Made it way more fun
As far as the comparison for the OP, the fox used 25.5" tall tires...

 

4.10

 

Ur stabbing in the dark.. multiply the OD ratio into the available rear ratios to see what the final will be. There are calculator websites the let you put in tire diameter that u can get from Specs on Tire-Rack. Don’t guess...

 

I owned a few of those over the years and they performed very well .....but.....they also have fairly small diameter tires. Tire diameter is a component in overall gear ratio.

Currently, I am building a ‘37;Chevy coupe with an 8.8 pony housing and tires are, I think, about 27”. My initial plan was 3.55, but I also had a set of 3.73 and ended going that way.

The Chevy will be powered by warmed over 250 Chevy six and a 2004R. It won’t be on the street for a few months yet, but I am anxious to see how that combo performs.

Ray

 

The numbers I posted were from a web calculator. Just figured I'd see what those with more knowledge and/or experience thought about my choices. Thanks for the replies. Good info to consider.

 

I have some 5:43's that will get you out of the hole fast but be gear bound just past the 1/8th mile. With a C4 three speed. Stick with the 3:55's for best economy and reliability. The low 1st gear of the AOD will give you some seat of the pants grunt and not totally kill the engine in a few thousand miles.

 

My OT DD uses 3.73:1 with OD trans & 235:75:15s, my 35 Chebby uses 3.54:1 with OD & 235:75:15s. Somewhere around 3.50:1 would be a good choice if available. There was a HAMBer (Banned) that only posted parts for sale, he had a variety of 8" pumpkins at one stage.

 

I see references to to the ratios of fuel injected Mustangs with knock sensors . Nothing ruins your day like a high geared car that detonates when climbing a hill

 

What is the goal here? Occasional driver that MPG isn't relevant? Keep in mind the OD only helps out on the highway, in town you're still going to be winding up the engine. I had a Crown Vic Police Interceptor. 351W/AOD/3.08. If it works for cops needing to chase down people......

 

My vote is for the 3.55's. I have used 5 speeds in every hot rod for 20 years. I usually run 29" tall tires. With the shorter tires, I think the 3.80 is too low for good highway cruising and fuel mileage.

 

3:55 and an AOD will be perfect

 

I think we drive our cars to what they are geared for , I don’t like feeling like I need to shift up when cruising down the highway. There’s a sweet spot with every car the taller the gear sweeter it is on the highway . I don’t like the engine sounding like it’s trying to throw a rod runing 75 + . I’d pick a gear that keeps the engine a little above 1900 at the speed you like to drive . Unless your into burn outs .

 

Forgot to mention, I work on the premise that engine RPM at 60mph speed should be between 1800 and 2100rpm (Sweet spot) with an OD transmission.

 

I had a 4.11 in my Morris Minor pro street car. It was a 5.0 with an AOD and it ran about 2300 rpm's at
interstate speeds . I had 295-50-15 tires that were 27inches tall.
When I first built it I had a 3.00 gear and it shifted in and out of overdrive when I was running in the 45-55 mph range. Very annoying . After I installed the 4.11 it cured that hunting issue.
In retrospect I could have used a 3,70 gear with no problem . My car was a lot lighter than your car
and was not stock with aluminum heads and a hot roller cam and 4 barrel carb. I used a B&M 2200 stall convertor and a B&M shift kit. Easy to install and gives better control to the transmission.

 

I guess I’m in the minority. I had a 327 and now a 283 in my Austin with 3.80 gear and a Th350. I turn 2800 to just over 3000 on the highway. Never thought about OD, they seem to be happy at that rpm. I remember factory cars coming with 4.11 gears and 14” tires and nobody worried about gas mileage.
Besides, gas is $2 a gallon. In 1970 it was 36 cents. That’s about $2.40 in today’s dollar. So I figure I’m doing OK.