Ruckstell ring gear in a standard ford diff

[Cody Winters]

Alright y'all got a real good one for you. let's say someone wanted to drop the rpms in their T at 40 mph
without installing the steep 3:1 gears and wanted to have say a 3.33 ratio. the 12 tooth pinion is meant to be used with a Ruckstell ring gear.
i'm wondering if it is possible to use a Ruckstell 40 tooth ring gear on a standard Ford diff. yes it has a recess in it but the 12-tooth pinion is also larger in diameter. theoretically it might bolt in with the proper shims. so that's my question for today. it seems logical but i want to know if it can be done

[Atomic Amish]

I was just reading through the Lang's catalog yesterday and wondering the same thing. So chimed in to follow along.

[speedytinc]

There is to much recess in a 3-1 gear to use a 12T pinion. A shim of about .090" is needed to get the mesh.
With that there is a higher risk of shearing the bolts.

Back to the original problem that is not a problem. 40 is a mild & comfortable cruising speed for a model T with stock gears.
Dont do it. You also lose some of your minimal braking ability, not to mention hill climbing ability.
I wouldnt go to a taller than stock ratio without being in a rux.

[Mike Silbert]

See these
https://www.mtfca.com/discus/messages/7 ... 1500352727

https://www.mtfca.com/discus/messages/2 ... 1344380034

and this old catalog snapshot

Screenshot 2026-01-17 110729.jpg (44.1 KiB) Viewed 364 times

Yes, you can play around with the gear ratio, it has been done since T's were new.
But the car is a whole balanced system. Go faster you need better brakes, more performance out of the engine, and more.
Then when you get on a tour you will be running up on everyone else and dropping back when hitting the hills.
The urge to go faster is normal but, will it make the car more enjoyable to drive?
My old cars remind me to slow down and enjoy life, appreciate things, and stop to smell the roses.
If I want to go faster I take a different car.
Mike

[TXGOAT2]

40 MPH is no sweat with stock gears. If you have a lot of vibration or noise at 40 MPH, something is wrong besides the gearing. I assume you have stock, or near-stock diameter tires. //40 MPH = 1600 RPM, which is a little under the horsepower peak.// 1800 RPM = 45 MPH, still a comfortable speed for a T engine in good condition and good balance, and very close to the horsepower peak with a stock cam or mild performance cam// 50 MPH = 2000 RPM... pushing it a little, especially with cast iron pistons.

[TXGOAT2]

Crankshaft bearing alignment is very critical in T engines. Aluminum pistons, good overall balance, and a good auxiliary oiler combined with a clean cooling system, modern one piece valves, a clean cooling system, and quality, multi-grade oil can provide reliable performance for many miles at 45+ MPH.

[Cody Winters]

40 MPH is no sweat with stock gears. If you have a lot of vibration or noise at 40 MPH, something is wrong besides the gearing. I assume you have stock, or near-stock diameter tires. //40 MPH = 1600 RPM, which is a little under the horsepower peak.// 1800 RPM = 45 MPH, still a comfortable speed for a T engine in good condition and good balance, and very close to the horsepower peak with a stock cam or mild performance cam// 50 MPH = 2000 RPM... pushing it a little, especially with cast iron pistons.

the reason for the question was mainly due to the fact of 1600 rpm being the equivalent to 2200 rpm in an A. the safe rpm limit. I'm looking at a 27 coupe that's all stock other than a more conventional manifold set up and holley nh. i'm not looking for performance, but efficiency and longevity. i've driven stock T's at 40 and it always seemed that 40 was a bit high in rpms. my thought was to drop the rpms down to the equivalent of 35 mph.

[Cody Winters]

to add to last comment, my plan is to at least add a Ford faithful oiler so it always has a good stream of oil flowing to the front.
the cooling system will be fully flushed and the radiator overhauled no matter what. my plan is to add the aluminum pistons and some new dipper rods from snyders to help keep the engine running smoothy day in and day out.

[TXGOAT2]

A T engine in good condition can handle 1800 RPM. The Model A is a completely different engine.
Early Ford advertising touted the power of the T engine, and stated that any speed from 5 MPH to 45 MPH, "If you want it" was available in high gear.

[TXGOAT2]

Adding a good auxiliary oiler is a good idea. I'd stay away from rod dippers. Never use thick oil in a Model T. Use a quality multigrade oil, like 10W30. 10W30 detergent oil does a good job in Model T engines and transmissions under most conditions. In cold weather, 5W20 is a good choice.

[Cody Winters]

Adding a good auxiliary oiler is a good idea. I'd stay away from rod dippers. Never use thick oil in a Model T. Use a quality multigrade oil, like 10W30. 10W30 detergent oil does a good job in Model T engines and transmissions under most conditions. In cold weather, 5W20 is a good choice.

I run 10w30 diesel spec oil in everything i own. as far as the dipper rods, i'm talking about the brand new one piece forged units from snyders.
I've seen the add on dippers come loose on rods before and i don't mess with them.
Not a fan of the mag post oilers as well as i am of the ford faithful since it can move a lot of oil even on an incline.

[Mark Gregush]

Rod dippers don't just feed that little hole in the bottom of the cap; they make more mist/spray inside the crankcase as they go through the dips in the bottom.

[TXGOAT2]

If you want a LOT of oil, use a Texas T type oiler.

[Cody Winters]

If you want a LOT of oil, use a Texas T type oiler.

not going to go that far, not interested in cutting into the hogshead,
but i do like having oil flowing to the front so a ford faithful will be fine for what i want.
so long as it can handle 40 mph consistently with no excessive wear and tear, i'm happy.

[Scott_Conger]

Since you mention adding aluminum pistons, I assume you have an original engine with cast iron pistons(?)

as an aside, I really like original engines and you most certainly can tell by sound and performance when an engine is original and when it is updated.

So, if you're wanting to just "go faster" and want to accomplish it with aluminum pistons and a higher rear end gear, I think you're in for an expensive disappointment. Your car is a heavy car and you will never make the power to consistently run 40 MPH with a higher rear end and a stock motor. A hill or a headwind will feel like an anchor has been thrown out...If you had a brass runabout which is quite a bit lighter, the equation would be a bit different...

Your plan is a common plan for nearly every new "T" owner - I don't know if you're new at this or not, but if a 40mph car as a your target goal, you should be looking for a '28 Model A. Very similar body, an engine that can do what you want, and you can do it in relative safety. 40MPH in a "T" always comes with more risk than I personally feel is justified driving a 100 year old car. Lots of things in a "T" can send you off this mortal coil and 40MPH will just do it faster and with more certainly.

The guys that say "oh, yeah, my car can do 40 on a bad day" are one of two types: MT 500 cars which have stock engines built to an nth degree of precision or guys who have high compression heads and upgraded cams...they are not guys who just put in some new pistons and an oiler. This isn't to demoralize you but to suggest that maybe some more study and asking questions might be in order, beyond "what is a good ratio to go 40MPH". A good start to a useful conversation would be to tell folks how long you've been in the hobby and EXACTLY what condition or age your present engine is in. Knowing this, you'll get better and more on-point advice beyond just 1 or 2 possible gear ratios.

Good luck and be safe

[TXGOAT2]

I believe I mentioned cast iron pistons. My car has aluminum pistons and modern type rings. It has run many thousands of miles at 40+ MPH since I bought it, with no evidence of any problems other than tire wear. Aluminum pistons of modern design offer reduced inertia loading at higher RPM and better oil control than stock type pistons and rings.

[TXGOAT2]

Well-adjusted coils and a timer in good condition will make for a smoother running engine at all speeds. Model Ts can have fuel delivery issues at higher engine speeds and loads. A high flow needle and seat assembly is offered that will correct this problem. Accessory fuel filters often aggravate fuel delivery issues under high demand situations. If you want your car to run at 40 MPH +, it will need to be in good tune and developing its full power potential. Closed cars are heavier than open cars, and just as important, the closed cars may have higher aero drag than the open cars, especially an open car with the top town and the windshield open. When you get up about about 30 MPH and over , aero drag becomes a significant issue. Aero drag increases very rapidly as speed increases.

[Original Smith]

I thought this post was on Ring and Pinion gears for use in Ruckstells?

[speedytinc]

I see since your first post you admitted you have a coupe. No question, you will not be happy with laller gears in a heavier T with a stock engine thats probably only putting out 15 HP on a good day. (Iron pistons with no balance) Your T wont pull taller gears. 40-45 is good speed for a T with a descent motor & an excellent ignition system. Thats right in the cam's peak performance. If you wanted more speed, I would recommend a rebuild, balance work, a precision ground cam & a high compression head. Then your motor can wind up tighter or possibly pull A 3.25 gear ratio.
I was following a fried down the freeway on my old knuckle head. I was impressed he was running a consistent 55 with a good but stock built motor. A full 20 HP motor. When he pulled the rear end he found a 10 tooth pinion. Doubly impressed.

[Cody Winters]

I see since your first post you admitted you have a coupe. No question, you will not be happy with laller gears in a heavier T with a stock engine thats probably only putting out 15 HP on a good day. (Iron pistons with no balance) Your T wont pull taller gears. 40-45 is good speed for a T with a descent motor & an excellent ignition system. Thats right in the cam's peak performance. If you wanted more speed, I would recommend a rebuild, balance work, a precision ground cam & a high compression head. Then your motor can wind up tighter or possibly pull A 3.25 gear ratio.
I was following a fried down the freeway on my old knuckle head. I was impressed he was running a consistent 55 with a good but stock built motor. A full 20 HP motor. When he pulled the rear end he found a 10 tooth pinion. Doubly impressed.

I own a bone stock 31 A pickup as my daily and i normally drive 40 mph on the highway, not interstate obviously and around 35 around town. my concern isn''t if the car can physically drive fast, but if it holds up. my concern is oil starvation or hitting a harmonic at 1600. the T in question is a car i'm looking at and it's as Henry made it, it might have been rebuilt but it's all stock. if a stock t can handle 40 mph with the 3.63 gears without problems, best to leave it alone

[speedytinc]

Yes, thats a wise conclusion.

Remember that unless you have a freshly rebuilt motor, Its less than the way Henry first released it.
An outside oiler is good motor insurance. The large internal oiler is more than adequate, but one never knows when it gets clogged until its too late. Wise decision leaving the stock gearing in.

[Allan]

As an aside, it is not good practice to add shim/s between the ring gear and carrier. Any shim fitted introduces another interface to allow movement between components. Adding shims behind the steel washers either side of the bronze thrust washers is a different proposition, as those components are not driven under load.
The same applies to rear axle hub shims. If you have to fit a shim, It is far better to fit one .010" shim then two .005" shims.

Allan from down under.

[RGould1910]

I can only add my experience. Just as background I've owned and mechanically restored about a dozen Ts. All stock open cars. I spin balance moving parts, use alum. pistons and Stipe 250 cams. All new babbitt, timing gears, ground crank, rebuilt coils, the works. I feel ok running them at 25 - 35 mph but no more. Have I pushed to 40 mph on occasion? Yes, but very rarely. I run stock Henry gears but have experimented with 3 to 1 and didn't like the reduced low-end torque or breaking. Considering the roads at the time, Ford prioritized low end power vs speed. As Scott observed, new T owners want to do things to make their cars run faster to keep up with modern traffic. Having been there myself, I can only advise to accept them for what they are and drive places that accomodate slower speeds.

[TXGOAT2]

A century on, in most cases, the integrity of original parts can be questionable, especially cylinder blocks, crankshafts, connecting rods, u-joints, frames, springs, rear axles, and valves. But a number of Ts have been run many thousands of miles at speeds at or above 40 MPH with no issues. No matter what you are driving, or where you are driving it, you'd best drive in such a way as to accommodate traffic and road conditions, and you'd best see to it that your vehicle, no matter what it is, is suitable for the traffic and road conditions you can expect to encounter, and that it is in good overall mechanical condition, and that you are operating it within its limits, whatever those limits may be, whether the vehicle's performance envelope has been expanded via modifications, or has been compromised by wear, decay, abuse, or whatever.
It's best not to skate in a buffalo herd, especially if you have bum skates.
For a "fast" T, I'd start with a late open car.

[Original Smith]

I would guess Ruckstell made ring gears for their rear ends, but have never seen one. What would have been the advantage?

[RajoRacer]

They did, Larry - I'm running two w/Ruckstell gear sets.

[TXGOAT2]

Ruckstells were installed in a variety of cars & trucks for a variety of reasons. The range of ring & pinion ratios offered were aimed at allowing customers to get the best advantage from their particular installation, be it a roadster owner looking for speed, or a fordor owner looking for better hill climbing and braking, or a trucker looking to better adapt his TT to his situation. An owner in Kansas would probably benefit from a different suite of ratios than an owner in Colorado would.

[modeltspaz]

Unlike my good friend, Larry "Original" Smith, I have actually seen a script Ruckstell ring gear. It was in a display case at the shop of a well known Southern California Model T mechanic. That shop is now closed and I do not know the current whereabouts of the gear.