This is a contrarian view: I run 4-1 gears with a Ruckstell in my 1925 roadster. Let me explain.
Several years ago I built up this roadster for mountain driving in Colorado (even though I live in Central NH). The engine was completely rebuilt and carefully balanced. I used a Stipe 280 cam, and timed the valves with a degree wheel. A lot of effort went into the valve train including honing the valve guides, Ford 351 Windsor exhaust valves, along with grinding the valve faces and seats to a runout of one half of one thousandths of an inch. I also used a Z high compression head. I run a stock NH swayback carburetor. It has a EE crankshaft. I understand from people who have dyno-ed Model T engines built in this manner that the horsepower is about 27 HP.
The Ruckstell rear axle was completely rebuilt using the best components available and a genuine Ford 4-1 ring and pinion. The rear break shoes are lined, and will both keep the car from moving or bring the car to a stop if moving.
The only other modification was changing the fuel line to the next size larger.
The car is powerful and fast. In low range the car will pull any hill. On two occasions the angle of the mountain road was so steep that the car stalled from lack of fuel even when the gas tank was FULL! I have a simple way of putting two pounds of air pressure into the gas tank, and once that was done the engine restarted and I motored up to the top of the mountain without further incident.
On level ground the car will do 52 mph on a continuous basis. It accelerates quickly, and by virtue of the 4-1 rear axle gears it comes to a stop sooner.
There are those who think that 4-1 gears in a Model T are too slow, and fear that revving up the engine is more likely to result in a broken crankshaft. In my experience broken crankshafts are attributable to 3 causes:
1. Inferior crankshafts (not all Model T crankshafts are equal. Crankshafts made by some forging companies seem to have a greater propensity to break than others).
2. Misalignment of the three main bearings and the ball cap. If a stock Model T engine has had some shims removed from under the main bearing caps, the chances are high that there is some misalignment of the crankshaft with the bearings. KR Wilson stated in his 1926 catalog that every motor should be rebabbitted. Experience has taught me he was right.
3. Lugging the engine. This is a very frequent cause of crankshaft breakage in Model Ts. The deflection placed on the crankshaft of a running Model T is amazingly large. In one instance one of my engines with perfect alignment and an EE crank developed a knock when the car was going up a hill after a complete rebuild. The engine was torn down 3 times before the cause of the knock was finally found. The flashing at the big end of one rod would just kiss the camshaft when the engine was under a heavy load. Grinding off just a little bit of the flashing eliminated the knock. The punch line was that when the engine was on the motor stand with the pan off, the little bit of flashing on the rod cleared the camshaft by a good .040"! Which says that under a heavy load the crankshaft can deflect or distort by as much as .040" or more. When a Model T engine is being lugged the deflection and distortion are exacerbated. Consequently many Model T crankshafts break either while they are being lugged or shortly after being lugged. 4-1 rear axle gears tend to reduce crankshaft lugging by keeping the engine rpms higher, and closer to the maximum power range of the engine.
I have found that the 4-1 gears with a Ruckstell serve very well. I am very happy with the car set up this way, even when I am not climbing the Rocky Mountains in it.
I have one more comment, and that is I would urge anyone thinking of making major modifications to a Model T should consider the following. Over the course of the many years that I have worked with the Model T's engineering document collection at the Benson Ford Research Center I have come to understand that a Model T is in fact a complex collection of a large number of interrelated and often times interdependent compromises. Many people who think that they can design a Model T better than the Ford engineers could do not understand or respect those built in compromises. Consequently they inadvertently break one or more of those compromises, sometimes to their regret later.
There is a reason Ford did not offer 3-1 rear axle gears for the Model T. The only alternative to the stock 3.63-1 rear axle ratio that Ford offered was 4-1. A Model T engine is much more likely to be in a lugging situation with 3-1 rear axle gears. There is only so much that a bent coat hanger can be expected to do. Think about it.
My car is too fast. I raise the risk factor significantly going down the road at 52 mph in a car without shock absorbers, with a transmission brake, that has a high center of gravity, 30" inch wheels and steering gears located underneath the steering wheel that is connected to the wheels through a series of shafts, tubes and pins. I keep the extra speed and power for use in an emergency when I need to get out of someone's way in a hurry.
I m not saying that someone should not make carefully thought out changes in their Model T. What I am urging people to do is to think through the consequences of their modifications before making them. A panic stop from 50 mph is not a good time to learn you made a mistake.
Sincerely, Respectfully Submitted,
That's a good lesson, Trent. Thank you for posting it.
I have a 1915 T Runabout that has been modified with a high compression head, hot cam, aluminum pistons, Ruckatell with a 3 to 1, etc. It is way to fast. Faster than that 100 year old car needs to be. It is not safe and is hard on the components like Trent says. I'm de-tuning it to improve its drivability and lengthen the components life. A stock Model T rebuilt properly is a pleasure to drive and will generally run for many miles without failure.
Sounds to me like you have been hanging around with Steve Coniff!
Excellent posting Trent B! Excellent posting.
I have come to the same conclusion Trent.
Along those same lines, I have also learned that messing with adding or removing spring leaves can have unpredictable, unwanted & dangerous results. Many folks try to lower a speedster by removing leaves, as I did. I nearly got in a serious accident with this scheme. Back to stock.
Let's not sell the engineers of the Model T era short, they were smart people, we should respect their choices and designs.
Trent, when you say "52 mph on a continuous basis", do you mean that's the car's cruising speed or the full-out top speed?
In this case the answer is both. The car can cruise at 52 mph but that is pretty near the full-out top speed.
Dan McEachern shrewdly guessed that I rebuilt that engine under the watchful eyes of a master Montana 500 engine builder and driver. But his Montana car cruises at 62mph.
I fully subscribe to your philosophy
Related to this is why I invented my "floating" transmission shaft. No I'm not soliciting sales of it
4 to 1 gears are great if they are in a car driven in hills, sand, or mountains, but my driving in the Houston area is on roads so flat that the state puts up signs in ditches telling the water which way to flow in the ditch. I, once, had a 26 fordor that came from the San Francisco area and it had 4 to 1 gears and a Ruxtell. I'm sure that they were needed in that area. My Grandfather's 27 coupe came from the Lake Charles area. I'm sure that area got paved highways long after other states did and the car was driven on dirt, muddy, or sandy roads most of its life, at least prior to WWII, but I have neither of those conditions to contend with. I have another 26 fordor which came from somewhere in Pennsylvania which has 3.63's in a Ruxtell and I am happy with it as it is a heavier car than the coupe.
what is the floating trans shaft you invented , curious . Can you post some pics or pm me?
Having a '25 with 4-dip pan and none of the added support of the 26-27s, I am very interested in a floating shaft also.
do you have any avail for sale still?
Contact me off line please
Thanks for the awesome explanation!
This info is interesting. My 26 Fordor finished this spring was given a 10 tooth pinyon because of being heavy and anticipated frequent hill climbing. Knowing it would therefore likely be run at higher rpm's, I had Rick Carnegie rebuild AND balance the transmission. To my surprise, it smooths out at 35 mph and runs easily at 40. I have had it up to 49 but with the steering and lack of stability I have not tried to see how fast it will go. The only power add ons are domed pistons. It has standard head and NH carb, neither modified.
What intake valve size do you have?
Sounds like a great running T. Did the car come with a Ruckstell or you decided to fit one? With a strong engine and 4:1, unless you go off-road or tow, I wouldn't think a Ruckstell is really necessary.