Technical Gear ratio

I would appreciate some input for a good banjo rear end gear ratio. This roadster pick up has a mostly stock V8 Flathead for power. The transmission is a 39 3 speed top loader with Zephyr gears . The pick up would be used mostly around town.
Thanks

 

3.70:1

 

Around town? 3.73 or 4.11:1 would do you solid. Much over 50 and you might not like it though.

 

If you have added some extra HP into it, 3.54:1 would be tempting...

 

I agree. FWIW.

Ben

 

Save your pop bottle money and get a quick change for it. Then you have a huge choice of ratios. Pick one and try it for a little bit. If you don't like it another set of change gears is relatively low cost. Plus there's the cool factor...

 

There were some 3.27’s out there for a while.

 

3.54 should be fine, you really don’t want that flatty screaming at you at 35- 50 mph your tires size will go along way. Tall tires you might have to jump up a bit to move from a stoplight with some zest before the ignorant ass behind you starts blasting their horns at you.

 

No complaints on my 354s in my 8ba dressed flathead . I'm a putter ,fine pulling off from red lights and on the road at 65-72 mph runs about 2800-3000 rpms , 225x75x15" rear tires , think they are about 27 1/2 " -28" diameter .

 

3:78 is the most common stock ratio, V8 60's were 4:44, I'm running 3:54 in my flathead 30 Sport Coupe and really happy with it. I'm running a 29" tire and at 60 it's turning 2460 rpms which isn't bad on a fresh flathead. It's easy to chirp the tires pulling out into traffic, good all around ratio.

 

What size and height are the rear tires? that we need to know!

 

The only flattie I remember is the 53 Ford station wagon I learned to drive in......
Since the flathead has bodacious long rods it has plenty of torque. Coupled with a light weight roadster and "mostly non-freeway" driving I would grab the tallest gear for made for the banjo rear!
Most recommend the 3.54:1 but anything taller would prolly be better.
Best guess
6sally6

 

I have started that processes . I bought a Rodsville center section. Not to sure what ring and pinion to start with , if matters.

 

Rear tire size will change a lot of things when it comes to your final ratio.

 

Seams most I've looked at lately for 16" wheels are 29"-ish tall. I'm sure you can find a calculator online you can enter all that in to and get desired RPM vs ratio.
D

 

You are in OHIO, very flat state .
I am a little hilly hear in the Northeast.
I am going from 4:11 to 3:54 this winter.
Stretch

 

I'd say that it may depend on how spirited you plan your "just around town" driving to be. Then how large of an area "just around town" encompasses. Looking at the map you could be in the Cleveland metro area and still be 70 miles or better from the other side of "town". Guys in the LA metro area can be 160 miles from the other side of the LA area which is two states away if you are in New England.
Still if most of your driving is within an hour of the house and you may or may not venture further once or twice a year what ever gears you feel will give you the around town poke you want are fine. I'd go 3.78 to give me a bit more friendly open road running than 4.11 though.
Of all the tire size/ gear ratio/ Rpm /speed calculators on the net this electric vehicle one is one of the simplest to use as long as you don't have to stop and factor in an overdrive. For a flathead with a 39 box it is perfect. Tire Size, RPM, Speed, and Differential Ratio Calculator (advanced-ev.com) Plug in any three and get the fourth.

 

I think the typical ratio for a qc ring and pinion for the v8 qc is 3.78:1. But you have change gear choices in approximately 0.10 steps, or 3.68 3.78 3.88 etc. And you flip the gears over ie big on the top, small on the bottom, and 3.68 becomes something like 3.90 on the 3.78 r&p.

 

Thanks for the correction, Moriarty.

For what it's worth, I've got 3.54s in my '35 pickup with a very slightly warmed over 59A and columbia rear. Great highway driver, though don't try accelerating up a hill in 3rd-over.

 

Is it the 32 roadster pick up in your album? Does it have a 32 rear? If so, late or early?

 

This is the correct answer!
Dave understands this concept. Since you have already sprung for the Rodsville, there is only one other thing to consider.......................Ring & Pinion.

While the Quickchange does allow you abundant choice of final drive ratios, you get the most versatility out of gear sets closest to your projected target.
If I were recommending the R&P for you (I guess I am), my suggestion would be either the 3.25 or the 3.54.
From conversations with other Rodsville owners, they use the 1.5" diameter pinion shank, not turned down to 1 3/8" like the Halibrand. This is a good thing because it allows use of the double cup Timken bearing set with no modifications to the case or the bearing race. The Halibrands used ball bearings which are much inferior to the tapered roller.

You will have to purchase the ring and pinion for the Banjo (not QC) and have the end of the pinion turned down for the rear cover bearing.

 

Yes it does have a 32 rear end at the moment . Also running 700 x 18" tires on the rear.

 

I have the '40 bells and a 4.11 6 spline ring and pinion .

 

If the 4.11 R&P are good, I would use them. If they need replacing I would go with the 3.25 or 3.54.

 

Hello,

When I had my first Flathead powered 1940 Ford Sedan Delivery, I had a ton of fun driving all over So Cal and coastal regions in the search for the best waves we could find. The stock Flathead horsepower at 80 was ok for most purposes on flat streets and downhill runs. Most of our driving daily was on flat ground, unless I picked up or took home my friends that lived in Bixby Knolls.

Then I had to drive uphill towards Signal Hill on three different major streets. As most people know when they see photos of the Long Beach Airport, the huge hill on the coastal side is Signal Hill. In those days, the hill was covered with oil pumpers and derricks. But the roads leading to the top and over to the other side were usually steep.

We know from earlier posts on the Model T speed runs on Hill St. from the early years through history. My 40 Ford Sedan Delivery with the stock Flathead power never made a run up that hill. The motor just did not have enough power to make it uphill. On the other side of the Signal Hill area, the main streets go uphill, but are steep and most cars could go up with extra effort. My Flathead needed all of the power I could muster on the leading grade to the top of the hill.

So, if there was no need to go up those hills as there were plenty of ways to get to our cruising grounds of Bixby Knolls, the Flathead was still the hit of our teenage driving. It was one of a kind and unusual for a teenager’s daily driver. Even our varsity football coach asked, “What the hell was I driving?” HA!

Jnaki

So if your daily driving is flat streets and once in a while steep grades, then your Flathead is fine. We had the stock gear ratio, which I thought was in the range of 3.55 to 3.78. The 3.55 in other v8 powered Chevy sedans were ok for flat street driving and long distance vacations. But, those guys did not race at Lion’s Dragstrip or did not care to race on Cherry Avenue. Hard acceleration runs, yes, but not a one-to-one drag race on the street.

Their 3.55 and 3.78 gears were fine for level driving and the post-Christmas runs uphill to the local mountains for the Chevy sedans. My low powered Flathead sedan delivery never made the uphill runs to the local mountains. The weekly runs down the coast always encountered the steep grade at el morro beach in laguna beach. With two-three people, plus old heavy longboards and beach stuff, downhill was fast, but uphill always necessitated a down shift to 2nd. If there was traffic, it was even down to first. That 80 hp just did not have it in the Flathead sedan delivery

I knew the limitations of power or lack of power from the Flathead, on angular hills from our So Cal steep grades on various roads down and up the coastline. YRMV