Checking R&P ratio with transmission in the car

[rcooled]

How can I verify what my R&P ratio is when the motor and transmission are still in the car? I had my stock '63 swing axle trans rebuilt with a 4:12:1 R&P and I just want to be sure of what's actually in there.

A search turned up methods such as jacking up the car, turning the engine over 10 revolutions by hand, and then counting tire rotations to figure the ratio. What gear should it be in when doing this? Can anyone clarify this method and give me some examples of how many times the tires should rotate when the motor turns 10 revolutions (in which gear) for the different R&P ratios?

Another post suggested putting the trans in 2nd gear and see how many motor revolutions it takes to turn the tires one complete rotation. It goes on to say that 8 turns indicate a 3.88:1 R&P, 8 1/2 turns is a 4:12:1 ratio and 9 turns is a 4.38:1. When I tried this, I got a full tire rotation with less than 6 revolutions of the motor, so something's not right here.

Does anyone have a reliable, easily-explainable method for checking the R&P ratio? All gear ratios are stock for a '63 swing axle trans: First 3.80:1, Second 2.06:1, Third 1.32:1 and Fourth 0.89:1.
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'63 Ragtop (current)
'65 Ghia coupe (totaled)
'67 Ghia convertible (current)
'69.5 Ghia convertible and
'62, '63, '65, '69 Bugs (all long gone)

[Bruce]

[rcooled]

[Bruce]

[EVfun]

For all Bugs with a tunnel type transaxle ('61 up) jack 1 rear wheel up off the ground turn the crank pulley until the timing mark of your choice is strait up. Mark the tire that is off the ground so you know where strait up is on it. Chock the car, put it in second gear, and release the e-brake. Turn the engine until the mark on the tire goes one full turn. If the crank is right back at the timing mark it is a 3.88 R&P, if it is 1/4 turn past the timing mark it is a 4.12 R&P, and if it is 1/2 turn past the timing mark it is a 4.37 R&P.
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[rcooled]

[VOLKSWAGNUT]

For someone who searches in the future... hopefully.

Another method.. ..easy to do while changing the fluid..

[rcooled]

[VOLKSWAGNUT]

[EVfun]

It is an excellent method Volkswagnut, but I think mine is a lot easier -- you don't have to drain and replace the gear oil, crawl under the car, or even use a jack stand. It's method is simple math, since 2nd gear is always 2.06:1, and if one side of a differential is held still the other side turns twice as fast. If you suspect you may have an aftermarket 3.44 Ring and Pinion you need to count the crank turns because it will be 3.5 turns to 1 turn of the wheel.

Turns, divided by the gear ratios between the engine and axle, time 2 for the differential turning only one wheel, will equal 1 turn at the wheel.

3.875 R&P if: 4 / 2.06 / 3.875 * 2 = 1
4.124 R&P if: 4.25 / 2.06 / 4.125 * 2 = 1
4.375 R&P if: 4.5 / 2.06 / 4.375 * 2 = 1
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[VOLKSWAGNUT]

[Windisch]

And someone did just 'discover' this thread (in 2017) to benefit from the knowledge contained in it! It's good to know all these techniques for determining final drive gear-ratio! Thanks for that prescient sharing of information!
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1973 Standard Beetle, 1974 VW/Porsche 914-4, 1.8 liter
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Der Volkswagen ist ein Ausdruck der deutschen Kultur der Allrad Art ...

[The only irrefutable evidence we have that intelligent life truly exists elsewhere in the Universe is the fact that so far it has NOT contacted humanity...]

[VWNate]

You guys are GREAT ! .
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-Nate

One last Beetle : 1959 #113 DeLuxe survivor ~ 36HP & full synchro tranny, 6 volts etc.