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Discussion Starter · #1 ·
Just wondering if anyone could explain why my rpm's are different when I have my overdrive turned off.I was towing a boat a few days ago with it switched off and was staying pretty close to 3000 @ 60 mph.Normal driving I stay at just under 2000 @ 60 mph(3.90 gears and 31'' bfg mt's)but when it kicks down ,say climbing a hill,it only goes to around 2500 thats with it maintaing 60 mph.Was it just because of the load the boat was putting on it.
 

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With O/D off, you are only in 3rd gear @ a 1:1 ratio (engine spinning the same revolutions as the drive shaft - this is assuming the torque converter is also locked). With O/D on, the truck shifts into a 4th gear. This gear allows the driveshaft to spin faster than the engine. I forget what the gear ratio is for the Tacoma's but it's less than 1:1.

:flamethro on
 

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Discussion Starter · #4 · (Edited)
yeah i know about the gearing ,what i'm getting at is when it kicks down it should be going to 3rd gear so why the diff in rpm's if it's in 3rd with the o/d off also.also what do you mean by getting burned(new to these forums but not to toyota's or mechanicing).
 

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Just wondering if anyone could explain why my rpm's are different when I have my overdrive turned off.I was towing a boat a few days ago with it switched off and was staying pretty close to 3000 @ 60 mph.Normal driving I stay at just under 2000 @ 60 mph(3.90 gears and 31'' bfg mt's)but when it kicks down ,say climbing a hill,it only goes to around 2500 thats with it maintaing 60 mph.Was it just because of the load the boat was putting on it.
http://en.wikipedia.org/wiki/Overdrive_(mechanics)

http://auto.howstuffworks.com/automatic-transmission8.htm

 

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The slight increase in RPM is not a gear change, it is the torque converter unlocking. You are still in overdrive, but the converter is unlocked. This allows the engine to make more power, but without the transmission shifting.
 
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