Shorter = lower gear ratio = bigger number numerically.

"shorter" being the time you spend in the lower gears.

There are so many "colorful" ways to describe gears.....

 

Ahhh now I understand.

 

It will be a stroker 304ci, and 250-280hp. Shouldnt that be enough?

 

I think you are building something that will be strong enough without being overkill. And your rear end choice should be a compromise of what your intended uses are. My buddy has a 56 F100 with a 460 in it backed up by a C-6 3-speed. To help with his mileage he installed 2.75s in the rear end. It only works for him because he has enough HP to pull grades at low RPMs. It seems to me that Y-block with an overdrive and a rear end using 3.50s would be about perfect. The only way to know for sure though is to build it. My 54 was built with 3.00s with a C-4 3-speed. Perfect for me, but not for everybody. I got those 3.00 gears from a fellow FTEer who bought them new and tried them out. He didn't like them so he sold them to me for the core charge of $18.00. Good luck, and enjoy the build. Jag

 

For the reasons Jag mentioned it is exactly why you should run the 3.70 or 3.89 gears. Horsepower does not move a vehicle, Torque does. Granted a stroked Y-block will produce more torque than a stock one but based on what you are saying your uses are you will be happier with the lower gears. You can get away with higher (lower number) gears running an auto than you can in a stick.

Running 3.00 gears at and below sea level (which is the Sacramento Valley) an automatic trans and never carrying a load will work for some but if you are going to spend the time and money to build a stroker motor I would think you would want to take advantage of it.

Don't take my word for it, put the higher gears in and then someone like Jag will buy them from you when you want to switch.

As far as the trans ratio in OD, if you have the trans put it in OD, mark the input and output shafts, rotate the intake shaft 1 (one) revolution and note how far the output shaft turns. Just under 3/4 turn=.70, just short of one revolution= .85.

Nothing personal Jag but based on his topography, his motor and the occasional loads anything less than the 3.70 gear I don't think he will be happy. I am all too familiar with the Sac area and I can tell you almost anything runs better there. (And I don't know what your running for a power plant.)

 

I normally shoot for 2000 rpm at 60-65 MPH and work backwards from there, only variables are the final trans drive ratio (OD ratio in the trans) and tire size.
For example 5th gear in my truck is .8, tire size is 235/50/18 which is an 85.6" circumference, so with a 3:08 gear I will be at 2000 RPM at 65 MPH in 5th.
You can use this calculator to play with numbers.

Speedometer, Gear Ratio, and Tire Size Calculator

 

The R-10 OD has a 0.70 OD gear ratio, see below. It is from the B-W OD Manual.

I vote for a ratio in the high 3's, in fact a stock '51-'52 Dana 44 with 3.92 gears would be about right (and would be a true bolt-in). In OD you'd be at 2.75, really loafing. If I understand correctly, you're going with 235/75-15's? That's what I run, tire rolling diameter is 28.1". Above 40 mph, you'd want to be in OD on flat ground, but any kind of long hill you'd want to kick down to 3rd. As I recall, that's about how OD-equipped trucks came from the factory?

 

The T85 only came with the R11 overdrive. The smaller transmissions came with the R10 overdrive.

R11 ratio is 0.72 to 1
R10 ratio is 0.70 to 1

I have had two 1966 pickups with T85N Borg-Warner transmissions with R11 overdrives. One had 3.50 rear ratio behind a 352 FE V8 and the other had 3.73 ratio behind a 300 six. I recommend the 3.73. It is easier to crawl around a corner in second with the 3.73 or lower rear axle (3.90 maybe a 4.11). First gear is not synchronized in any transmission with Borg-Warner overdrive so down shifting into first is best done at a stop.

 

Yep, I can tell you from experience 3:50 is too high. For what you describe I'd go with the 3:89. I need to change out my 3:50 for a 3:70 or 3:89.

 

I have a 56 panel with a stock Y block, 3.92 rear gears, and 3speed with OD

I'm running stock tires (6.70x15) and I can run 75 mph all day long and get 17-18 MPG!

 

Often we get hung up in trying to reduce cruising rpm, thinking that this will lengthen the life of the engine and increase mileage. Often this just isn't true. It sounds like this engine is making some horsepower and maybe is not all stock. If a cam is being used, it will move the power band up even more. Any time you place cruising rpm well under the peak torque of the engine, the entire combination becomes a lot less fun to drive. In addition, the mileage and longevity may actually suffer because the engine is being lugged.

 

Here is what I'm running. These are the numbers: @ 75 mph I will be running 2,151 rpm's. This is based on the following: Ford 408 Stroker, T5z transmission with .73 5th gear, 3.07 differential and 235/50 R17's. Which is good enough for me.

_________________________________________
48 Ford F1 - Darkside
46 Ford Tudor - Street Rod

"Happiness - 3 pedals and a 5 speed"

 

Thanks ALBUQ F-1 I am actually starting to swallow the 3.7 or 3.89 gear as is showed that I had puten in .85 as OD but it´s most likeley on 0.7 (most sources say 0.7 and then the 3.7 or 3.89 seems to owrk just fine. even at city speed and cornering on the second gear.

Correct me if I am wrong but wasn´t it a DANA 41 in F-1 from 48-52?

I have identified my present axel to a Dana 41 see bellow.



What do you all think would a Dana 41 handel 250-280 "maybe" 300 if I am lucky?

 

Thanks

What rpm are you running at, at 75 mph?

 

I know by casting numbers that I have a R10 but I cant find any number on the trans that say T85, Whats the name of the " smaller transmission" i have the one with straigh "hatch" side if you get me?

EDIT: