1930 pickup driving speed

M

mll1446

Senior Member
I have a 30 pickup what should be top driving speed I can. Run at 30-35 but after that it seems to be pushing it.
 
It depends on several things, but what rear axle ratio do you have. For mine, 40-45 is nice.
 
If you have the 4:11 rear end ratio that was used on some trucks, then that would explain the lack of road speed. Most Model A's are comfortable at 40-45 MPH.
In the photo, the speedometer drive to the left is the standard 3.78:1 ratio. The drive on the right is the much slower 4:11.
Look under your truck at the front of the driveshaft where it couples to the transmission and see if you can read any numbers on the speedo drive.
This is all assuming that your truck has never had the speedo drive swapped out, or rear end ratio changed. But if everything is still original, then the ratio on your speedo drive will tell you what rear end ratio you have.
If you do have the 4:11 rear end, you can swap out the ring and pinion with either a 3.78 or 3.54 ratio ring and pinion. Your truck will gallop then.
 

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Examine the rear axle "torque tube." (Tube connecting the universal to the punkin)

On my 4:11 March 1929 Truck this tube was "tapered" uniformly from universal to gearcase. Most Model A standard have a "short taper" and then straight for the rear 2/3rs of the tube.

I have heard that early Model A ("AR" style) also utilized the continuous taper tube. So perhaps the indicator is not universal?

On the other hand - Ford may have used up "old stock" tubes as a way to make distinction in the assembly line between the slower 4:11 and the more common and widely applied 3:78

The 4:11 WAS more common on trucks.

I wrote this in 2014 on how to tell the ratio from external actions...

The only SURE way to confirm which of the two original ratios you have is to block up one rear wheel and then using the crank, turn over the entire system starting at the engine end. Count the number of turns in at the crank versus the number of turns out at the wheel - then account for the fact that a differential will make the rear wheel turn twice as fast if you're only turning one wheel of the two.
Click to expand...
You could do 10 turns of the engine and get out 4.86 or 5.29 turns of one wheel. (10 x 2/3.78 = 5.29)

Joe K
 
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mll1446 said:
It says 9-34. 19 on speedometer
Click to expand...
I.e. 3.78 by the speedo gear.

But its hard to know. Until perhaps the mid-90s, replacement gearsets were not readily available and the gears were first available in the most widely used 3.78 setup.

I put a 3.54 under my 29 CC Truck in the early 1980s - and 3.78 was all there was then. My speedometer today reads possibly 4 mph LOW at highway speed.

Dad followed me in his car while I was driving the Model A to New Hampshire in the early 1980s. On our arrival he says to me "Don't you want to keep that Model A under 60 mph considering your brakes are none too good?" I never drove the car above 55 by the dial.

So I would say its very unlikely given your actual driving sensation that you have a standard original differential gear.

I'm looking at the Service Bulletins Page 393 and production driven speedo gears then was:
A-17271-B Gear for 9-24 and 10-37 (3.77 & 3.78)differential ratios = 18 teeth
A-17271-E Gear for 9-37 (4.11) differential ratios = 20 teeth.

Page 415
A-17270-D Gear for smaller tires of 1930,31 Model Year (3.78 ratio) = 19 teeth.
A-17271-E Gear for 9-37 (4.11) differential ratios = 20 teeth continue.

So it may be possible to remove the cap, count the teeth, and confirm what the speedo gear case says.

But this still doesn't confirm what the rear axle ACTUALLY is.

Joe K
 
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Do you have a GPS or speed app on your phone? If so, compare it to your speedometer to see if it matches.
 
I have a '31 RDPU with a 3.54 rear end (definitely not stock) and it is comfortable at 55 mph. Much above that and the front fenders act like airplane wings and the front end becomes very light and it feels like power steering. A passing semi or a canyon the crosses the highway is definitely easily noticed.

If you are toping out at 30-35 start by checking to see if you have full travel on the throttle. Then check the timing.

Charlie Stephens
 
To check the rear end ratio, jack up one rear wheel. Put the truck in high gear. Put a mark on the rear wheel, a piece of masking tape will do. Crank the engine over using the hand crank while keeping track of the number of turns of the crank and the number of turns of the rear wheel. When you get to 20 turns of the rear wheel, divide the number of turns of the crank by 10 and that is your gear ratio. For instance, if the crank turns 37 and 3/4 turn then the ratio is 3.78. If it turns 41 and 1/10 turns then the ratio is 4.11. To make this easier you can take the plugs out and if the rear brakes are dragging you can temporally back out the adjusters.
 
Well that was all interesting information and I thank all you who contributed.
My ute, tourer or coupe won’t make anywhere near the speeds I hear you blokes speak about so I now know how to check those 3 vehicles. I am always aware of the fibs that are told and have responded in previous responses from other contributors. And I have always said, quote-
More lies are told by fishermen
More lies are told by farmers on crop yields
More lies are told by Model A owners on the speeds of their motorcars.

I might review that now.
 
nkaminar said:
To check the rear end ratio, jack up one rear wheel. Put the truck in high gear. Put a mark on the rear wheel, a piece of masking tape will do. Crank the engine over using the hand crank while keeping track of the number of turns of the crank and the number of turns of the rear wheel. When you get to 20 turns of the rear wheel, divide the number of turns of the crank by 10 and that is your gear ratio. For instance, if the crank turns 37 and 3/4 turn then the ratio is 3.78. If it turns 41 and 1/10 turns then the ratio is 4.11. To make this easier you can take the plugs out and if the rear brakes are dragging you can temporally back out the adjusters.
Click to expand...

A shortcut method of determining the rear end gear ratio is to turn the crank until the rear wheel makes exactly 2 revolutions and then measuring the crank revs. If the crank turns 3 and three quarters revolutions, then you have a 3.78 gear ratio, and so on. I never thought of doing 20 revs on the wheel and dividing by 10. Kaminar's method would be more accurate. Thanks for the info!
 
More lies are told by Model A owners on the speeds of their motorcars.

Gas mileage...

Joe K
 
I'm comfortable driving my '31 CCPU at 30-35 mph, I'm not a "go fast" type of person. Even driving my modern car on the highway I drive at or under the posted speed limit.
 
If do not have the 4:11 rear then you should expect a properly rebuilt A to run 60 MPH comfortably, get in the low to mid 20's for fuel mileage and brakes that top confidentaly.

This requires a car properly restored mechanically to factory specs.

Period, end of story. This is based no what Ford advertised, what people found the car would do on crappy roads of the day and what people who have taken car to restore their cars mechanically find they are able to do today.

Many people will tell you the A is a 45 MPH car. Most of the cars I see, where the owners make that statement, are unsafe above 25 MPH in my experience.

The A is a car you should not feel bad about driving hard, putting in the garage knowing the next day it will start and be ready to be run hard again. Thats what happened when they were new.
 
Kevin I agree. It’s a matter of properly restoring all the components, brakes, drive train, etc and all dialed in well. They can perform splendidly well day after day.
I actually think many are done much better today than they were 35-50 years ago. Thanks to our Parts suppliers for keeping things going to us to help with proper rebuilding and restoration.
Larry
 
Mike Peters said:
If you have the 4:11 rear end ratio that was used on some trucks, then that would explain the lack of road speed. Most Model A's are comfortable at 40-45 MPH.
In the photo, the speedometer drive to the left is the standard 3.78:1 ratio. The drive on the right is the much slower 4:11.
Look under your truck at the front of the driveshaft where it couples to the transmission and see if you can read any numbers on the speedo drive.
This is all assuming that your truck has never had the speedo drive swapped out, or rear end ratio changed. But if everything is still original, then the ratio on your speedo drive will tell you what rear end ratio you have.
If you do have the 4:11 rear end, you can swap out the ring and pinion with either a 3.78 or 3.54 ratio ring and pinion. Your truck will gallop then.
Click to expand...

My turtle has the 9-34 on it with no extension stenciled anywhere on it. How would I interpret that sequence?

Edit: Never mind. That's a 3.78. It's a 9 tooth pinion and 34 tooth driving gear.
 
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