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sltdak

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Discussion starter · #1 ·
Like title says, here goes; if I have a 4spd auto tranny with O/D, and O/D is an extra gear or a higher gear, do I have a 5 spd auto or no? In either case, please explain.

Another question; if I have a 4spd auto with O/D, would there be a problem with my tranny shifting out of 3rd and into 4th with O/D off? It seems as if when I turn O/D off, my truck won't shift into 4th.

One more question; why do auto trannys have to have an external fluid cooler (in the radiator), while manual trannys don't? Please explain this one as well.

Thank you.
 
#2 ·
when OD is OFF it won't shift into 4th, as overdrive is the 4th gear. They call it a 5 speed because there are (2) second gears. Depending on how you accelrate as second is the passing gear, your speed and rpm's will determine which 2nd you go into. Overdrive is an extra gear. You don't have to have an external cooler, by keeping the temps down you maintain the fluid from burning up thus resulting in longer life of fluid and less frequent changes. An automatic tranny has WAY more parts than a manual. More parts=more friction=more heat= NEEDS a cooler!!
 
#3 ·
what do you mean two second gears? there is only one. Its a 4 speed trans, with 3 speeds and an OD making the 4th speed. "4 speed trans with OD" simply means that the 4th speed is OD.
 
#5 ·
the 4th gear is the OD...plain and simple:drive:
 
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Discussion starter · #8 ·
ucimaplaya2 said:
what do you mean two second gears? there is only one. Its a 4 speed trans, with 3 speeds and an OD making the 4th speed. "4 speed trans with OD" simply means that the 4th speed is OD.
Click to expand...
Silver Bullet said:
the 4th gear is the OD...plain and simple:drive:
Click to expand...
So, my 4spd transmission with O/D, is just a 4spd transmission or a 3spd transmission with an extra 'gear'?
Is there any difference between my 4spd with O/D and a regular 4spd without O/D?
 
#9 ·
sltdak said:
So, my 4spd transmission with O/D, is just a 4spd transmission or a 3spd transmission with an extra 'gear'?
Is there any difference between my 4spd with O/D and a regular 4spd without O/D?
Click to expand...
normally an overdrive gear is extrodinarily wide...alows your engine to cruise at low rpms to conserve gasmillage, and be easier on the engine...yes you could say that yous is a 3spd with an extra gear, but it is tradisional to just call it a 4 speed because technicly the od gear is a speed too...make sence?...good question though! :drive:
 
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#12 ·
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#13 ·
sltdak said:
One more question; why do auto trannys have to have an external fluid cooler (in the radiator), while manual trannys don't? Please explain this one as well.

Thank you.
Click to expand...

only thing thats gets hot is the clutch on a manual trans (i believe). the auto trans uses the fluid to make the truck move due to how its made to run through it and the torque converter. without it, the truck would just sit there. this fluid gets really hot, and fast too. so the auto makers make the fluid run through the anemic cooler thats in the radiator (in an attempt) to cool the fluid down. imo, and external cooler works better cause your allowing the heat to disipate and radiate right from the air, and not into another type of heat exchanger type device. the fluid in the rad is like 195-200*. its obviouse the trans fluid may get down to this temp, but even that isnt good enough to promote long life for it. optimal temp fro the trans is between 160-185.
 
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#14 ·
ucimaplaya2 said:
what do you mean two second gears? there is only one. Its a 4 speed trans, with 3 speeds and an OD making the 4th speed. "4 speed trans with OD" simply means that the 4th speed is OD.
Click to expand...
think he was referring to the new 5 speed autos that are in these trucks now..(2006+). 545rfe's and such.
 
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#15 ·
bondslayer said:
when OD is OFF it won't shift into 4th, as overdrive is the 4th gear. They call it a 5 speed because there are (2) second gears. Depending on how you accelrate as second is the passing gear, your speed and rpm's will determine which 2nd you go into. Overdrive is an extra gear. You don't have to have an external cooler, by keeping the temps down you maintain the fluid from burning up thus resulting in longer life of fluid and less frequent changes. An automatic tranny has WAY more parts than a manual. More parts=more friction=more heat= NEEDS a cooler!!
Click to expand...
and i beg to differ about a stock auto trans not needing a external cooler. seen to many stock transmissions take a shit because of internal failure due to heat. adding a cooler is one more step to making your vehicle last that much longer
 
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#17 · (Edited)
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