Is There Way To Check Differential Gear Ratio Without Disassembly?

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Model T Ford Forum: Forum 2016: Is There Way To Check Differential Gear Ratio Without Disassembly?
Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert Brough on Sunday, April 24, 2016 - 12:53 pm:

Got a speedster drivetrain that I will probably post for sale in the near future as I am not going to use it on my current project.
It has a shortened driveshaft and a locked truck cast iron Warford transmission attached to it. It was suggested that it may have a 3 to 1 gear ratio in the rear differential as that would be a good set up on a speedster with a Warford.

But I don't really want to tear down the whole rear end to count teeth on the ring gear. Is there a way to calculate wheel rotations to the driveshaft rotation to accurately represent the gear ratio that is on this rear end?

I'll hang up and listen.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gary Schreiber- Santa Isabel Ecuador on Sunday, April 24, 2016 - 12:55 pm:

I have used wheel to driveshaft rotation for approximate ratio.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert G. Hester Jr., Riverview, FL on Sunday, April 24, 2016 - 01:32 pm:

Lock one axle so that it can't turn, leaving the other axle free to turn. Rotate the drive shaft until the freed axle makes exactly two turns. The number of turns of the drive shaft is the ratio.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Sunday, April 24, 2016 - 04:35 pm:

The Warford transmission already has an overdrive, so it's unlikely to find 3:1 gears in a rear axle that has been used with it - few T engines would be able to pull that in overdrive, so most likely you'll find the std 3.64:1 ratio.

When checking the ratio you must either disconnect the transmission or make sure you have it in direct. The shift pattern is a backwards lower case h. To the right and up is underdrive, straight down all the way is direct, and then halfway up, over left, and then down is overdrive. Halfway up you can wiggle the shifter left and right and the transmission is in neutral.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert Brough on Sunday, April 24, 2016 - 10:45 pm:

After reading some other threads on this subject that I couldn't find before, can I do this?
Put U joint in front of Warford
Warford is in permant neutral
no engine in car
roll the car backwards or forwards and count the wheel revolutions and the U joint revolutions?

6 complete revolutions of the U joint and 2 complete revolutions of the wheels give me a 3:1 ratio?

If so, will the wire wheels and tires currently on it and/or wooden wheels give me a different ratio with the same differential gears?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert G. Hester Jr., Riverview, FL on Monday, April 25, 2016 - 03:04 am:

Robert, if your u-joint is exposed you can roll the chassis until both wheels make one turn and if your u-joint makes three turns then you have a 3:1 ratio.
When I mentioned two turns earlier that was assuming that only one axle would be turning.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Monday, April 25, 2016 - 03:14 am:

"Warford is in permanent neutral" - not sure I understand you there? If the rear axle is in a chassis and the cast iron Warford also hangs there on a crossmember brace but no engine, then the front u-joint wouldn't be connected to the rear axle if the Warford is in "permanent neutral"?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert Brough on Monday, April 25, 2016 - 08:06 am:

Hmmmm... perhaps it is stuck in permanent gear? The rear axle keys have been removed to make it a "roller", so perhaps that is why. I'll put some axle keys in and a U join in the front of the Warford and see what is going on. If I can get it to move, I'll count revolutions. If not, then I'll probably just disconnect the entire drivetrain and move on with the one I'm rebuilding now for use without the Warford.


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