I'm a novice and need to ask stupid questions for all you experts out there. I have a 1939 Ford half ton, no engine. Looking for an 8ba to be modified to achieve and sustain highway speeds with rpms in the low 2000 range. What transmission do I need and what modifications to my 4.11 rear end banjo gearing be required? Thanks.
Getting Drivetrain Correct
- Thread starter NoviceLou
- Start date
19Fordy
Well-known member
This will help:
http://wallaceracing.com/calc-gear-tire-rpm-mph.php
http://wallaceracing.com/calc-gear-tire-rpm-mph.php
hueyhoolihan
Well-known member
the simplest and probably the least expensive way to get "longer legs" on an automobile is to put on tires with a larger diameter. sometimes it's possible to get away with just buying new rear tires, although handling may suffer.
for instance, if the tire to be replaced has a diameter of 25" and is replaced with a tire of 26", there will be about a 4% increase in speeds at all RPMs and in all gears. (one inch is one twenty-fifth of an increase on a tire with a twenty-five diameter which is equal to four percent.)
for instance, if the tire to be replaced has a diameter of 25" and is replaced with a tire of 26", there will be about a 4% increase in speeds at all RPMs and in all gears. (one inch is one twenty-fifth of an increase on a tire with a twenty-five diameter which is equal to four percent.)
tubman
Well-known member
Rear end gearing is the final answer here, along with final tuning with different-sized tires. Also, your location with local terrain characteristics are important. You would gear different for Florida than you would for Denver. Unfortunately, we have no idea where you are, so it's going to be a little hard to make good suggestions. A lot of new members think that location is not important and leave it out. Believe me, It's there for a reason.
Me? With a strong running modified Merc in my '51 coupe, I get along just fine with 3.55's and 225/75R15 and no overdrive. An OD is next and will complicate the decision.
Me? With a strong running modified Merc in my '51 coupe, I get along just fine with 3.55's and 225/75R15 and no overdrive. An OD is next and will complicate the decision.
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Donaldoster
Junior Member
get a mitchell overdrive. they are bullet proof and great folks to work with
hueyhoolihan
Well-known member
when i had a 2007 porsche cayman with a five speed, i would be doing about 2700 RPM at 70mph. pretty low gearing for a 21st century performance car, IMO. the upper 2000's is very doable for long days in the saddle.
i've experienced enjoyable 3000 mile multi-day tours across the Sierras and Rockies in both a 1953 MG with a 4.55 diff that was pulling 3500RPM at 55mph (although to get to the 4.55 i had to swap out the standard 5.125! ha), and a 1967 MK2 Jaguar sedan turning 2700rpm at 62mph.
i don't anticipate any gearing disappoints in my standard 1941 ford when i take my first cross-country tour.
i've experienced enjoyable 3000 mile multi-day tours across the Sierras and Rockies in both a 1953 MG with a 4.55 diff that was pulling 3500RPM at 55mph (although to get to the 4.55 i had to swap out the standard 5.125! ha), and a 1967 MK2 Jaguar sedan turning 2700rpm at 62mph.
i don't anticipate any gearing disappoints in my standard 1941 ford when i take my first cross-country tour.
tubman
Well-known member
And almost as good as a properly set up Columbia" And expensive.
Seth Swoboda
Well-known member
The sock 221 cubic inch engine is plenty of power. If you want to do the job for the least amount of money, install 3.54 or 3.25 gears in your rear end (depending on if you live in a mountain area or flat). Rebuild the transmission using a 29 tooth cluster and 15 tooth main gear. You'll be all set to cruise at 65+ mph for a fraction of the cost of any of the overdrive units.