727 gear ratios?

Griffon

Griffon

Member
Another newbie question ( it seems like I've asked a basic question on each of the tech sections:blush2:). What are the 727 gear ratios? I've finally got project old school prerunner on the road but can't seem to break 60mph. I've got a 73' with 3.73's and 32" tires. I've had my share of dodge ramchargers with the same(I think) trans and have been able to keep up with traffic with around the same tires. Are the ratios different on some scouts?
 
In answer to your question all 727 transmissions have the same ratios internally. The final ratio for the trans is 1 to 1 so if you are in 2h on the t/case and you have 3.73 axles you are 3.73 to 1.
You can verify the axle ratio by the tag on the cover or by pulling the cover and checking the numbers on the gears.
My 74 had the auto and 409 gears with 33 tsl's. I could keep up with traffic ok , trust me it was no speedster but it wasnt wound out either. No tach to verify rpms just old ears..
You also need to measure your 32 in tires to verify they are actually 32 in tall. My buddy has a set of m/t baja claws that are 35 12.50 15 they measure a slightly small 35 at 33.6 and thats on the proper rim and inflation so your 32's May actually only measure 30 or 31 which in turn lowers your final drive ratio
and as Jeff stated all scouts were spec ordered with many different axle ratios from the factory
 
Smaller tires do lower the final drive ratio as mentioned, but even if your tires measure out a smidge less than 32" under the weight of the vehicle, that's still considerably taller than the stock tire offerings when your Scout was new. So, your bigger tires even if smaller than advertised have increased your final drive ratio. Your 3.73 axle ratio is probably more like a 3.54 with those tires. Could it be a case of the big tires being too heavy for the engine to overcome? If you had a 4-popper maybe. But a "healthy" 258 should still to be able to get you around 70 + mph on a flat. The other thing to consider is the accuracy of your speedometer. For one thing its damn old, which calls accuracy in to question. The other thing is, larger tire size will throw off the speedo gear ratio, making it read slower than the actual vehicle speed. Have you measured your speed with a gps? Maybe you're going faster than you think.
Other considerations...how does your transmission shift? Are you able to feel it kick or shift down when throttle pressure is increased in response to load such as cruising up a steep hill or trying to pass a slower vehicle? Are you physically able to achieve wide open throttle, both by working the linkage by hand at the carb and when you step on the gas pedal? Perhaps something is out of adjustment, binding up, or broken in between the carb, trans, and gas pedal arm. So give all that stuff a good pondering and get back to us.
 
Duh, 1 to1 final trans ratio with no overdrive:blush2:. For some reason I was thinking the transmission was a gear reduction at third gear like a transfer case. 1 to 1 w/out overdrive. Thanks for your responses.
 
A planetary gearset is available for the 727. I had installed one of these on my Scout and t'all. Lowers 1st and 2nd gears to 2.74 and 1.54, respectively.
 
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