HELP ID: 1934 Ford V8 rear axle / diff ratio

[fordson]

Hello Fordbarners,
i own a Canadian produced 1934 Ford V8 RIGHT HAND DRIVE coupe, that was assembled in South Africa.
Iam trying to figure out the ring and pinion gears and ratio with regards to my original rear axle.
I found the following information:
" Althought they are sometimes impossible to read, the fatory gear ratio is stamped on the bottom of the rib of the centre section; the first number represents the number of teeth on the pinion, the second the numbers on the ring gear.The ratios were: 3.54, 3.78, 4.11, 4.44, 4.55 "
Unfortunately i could not find any of these numbers on my rear axle.

What i did find i have taken photos of, showing:
1) stamped number: 34 on the web support of the centre section
2) stamped number: 1.38
3) stamped number: 1
4) stamped encircled letter: A
none of these numbers look as if they were cast !

Maybe the number 1.38 is refering to the commercial Pinion Locking Key - 1.38 Long - Ford 1 Ton Truck - (1940 - 47) and commercial cars (1942 -47). That was the only information i could find regarding that particular figure !

If anybody could help and give any information on the possible ring and pinion gear ratio,i would be gratefull. I was hoping for a 3.54 (wishfull thinking) !
Thanx for the help.
Regards Fordson

[jimTN]

Its probabily a 0/34(3:78) drain the oil out, stick a rag thru the fin hole and wipe off several teeth, mark one with chaulk and use a screwdriver thru the bottom hole to turn the ring gear, or reach over and turn a wheel counting the teeth.

[ford38v8]

If your odometer is registering correctly, then use the chart on the link below to determine your ratio. Match the number on your speedometer gear housing to the chart. You'll have to lift the floorboard to see the housing attached to the torque tube.

https://www.fordbarn.com/forum/attach...7&d=1351240537

If that doesn't produce results for you, then use this method:
Remove all spark plugs.
Transmission in neutral.
Hold your thumb over one spark plug hole to determine TDC power stroke turning the fan by hand.
Jack up one rear wheel.
Transmission in high gear.
Have a friend mark the top of the tire with chalk.
Have your friend turn the wheel round, counting the revolutions exactly, until the power stroke blows on your thumb again.
The exact number of revolutions including the last partial revolution is then divided by 4, which will give you the gear ratio.

Explanation: Power stroke to power stroke = 2 engine revolutions
One wheel turning = 2 engine revolutions
2 + 2 = 4.
Wheel revolutions divided by 4 will give accurate results.

JimTN has also posted a good method. You needed to change that gear oil anyway, didn't you?

[BrianCT]

Originally Posted by ford38v8

If your odometer is registering correctly, then use the chart on the link below to determine your ratio. Match the number on your speedometer gear housing to the chart. You'll have to lift the floorboard to see the housing attached to the torque tube.

https://www.fordbarn.com/forum/attach...7&d=1351240537

If that doesn't produce results for you, then use this method:
Remove all spark plugs.
Transmission in neutral.
Hold your thumb over one spark plug hole to determine TDC power stroke turning the fan by hand.
Jack up one rear wheel.
Transmission in high gear.
Have a friend mark the top of the tire with chalk.
Have your friend turn the wheel round, counting the revolutions exactly, until the power stroke blows on your thumb again.
The exact number of revolutions including the last partial revolution is then divided by 4, which will give you the gear ratio.

Explanation: Power stroke to power stroke = 2 engine revolutions
One wheel turning = 2 engine revolutions
2 + 2 = 4.
Wheel revolutions divided by 4 will give accurate results.

JimTN has also posted a good method. You needed to change that gear oil
anyway, didn't you?

Or is it ' multiply the tire revs by 4'?

[Straightpipes]

Just count the teeth on the ring gear. Those numbers don't mean anything.

[ford38v8]

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Brian, ya made me think...
4 stroke engine = 2 revs per power stroke
1 wheel jacked up = twice the revs.
2 + 2 = 4.
Divide by 4.

Now i got a headache.

[Terry,OH]

Clean off the area in front of the 34 and divide the two numbers. 9-34 is 3:78

[ford38v8]

Originally Posted by Straightpipes

Just count the teeth on the ring gear. Those numbers don't mean anything.

Beg to differ. Those numbers are the ratio.

[DavidG]

Terry and Alan are correct. That's why the numbers are stamped there (so you don't have go through gyrations to know what the ratio is of the gears inside (assuming that the gears have never been changed since the vehicle was built).

[whizzernick]

To my knowledge Ford never made a 3.78 ratio for 34 Ford .

[DavidG]

It's listed in the '34 chassis parts catalogue: 404209-B Gear (rear axle) and pinion assembly (matched) 9:34 (with a typo of 32 instead of a 34).

[jimTN]

If you know the number of teeth on the ring gear, you know the ratio.
39=3:54
34=3;78
37=4:11
40=4:44
41=4:56 supposed to have been used on 41 4cyl
these numbers apply to all closed drive shaft models

[fordson]

Wow, overwhelming reply and a lot of great information, thanks a lot guys.
I hope Terry, Alan and David are correct. I will clean some paint and dirt of the front section of the number 34 to see if i can identify another number.
If that doesnt work ill do as Brian, Jim and ford38 have suggested. Good instructions. Regarding the maths: i will have a headache !!
Ill let you know what i find, a 3.78 ratio would be great.

Randolf

[scooder]

From the web on the bottom of the centre section, with the 34 stamped in it means that the centre section was originally fitted with 3.78:1 crown and pinion. That is the fact, all the other numbers mean squit.
Wether it still has those gears in it, is up to you to count stuff. And the easiest way is the mucky way, gonna smell in there too.
Martin.