Which tranny best for engine?
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Which tranny best for engine?
Which type of transmission makes life easier on an engine - a (properly driven) manual or an automatic? My first thoughts: the torque converter in an auto "cushions" the engine, but the manual avoids the frequent high revving caused by the auto shifting down all the time, whenever the throttle is wide open... what do you think?
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From: USA
For a vehicle driven on the street, I would think a manual would be easiest on it. Less rpm's because no torque converter slip, no power loss through the converter, less heat from the trans, more gears (typically) and closer gear ratios keeping the engine in the powerband better. The manual trans is much better suited to towing than the auto.
For an off-road vehicle, I would think an auto could be better because of the torque converter cushioning the jolts, as you stated, and no clutch wear issues from feathering the clutch. Most rock crawlers prefer an automatic and super low transfer case and axle gears, sometimes using 2 transfer cases for a double-low ratio. The auto is easier to crawl and climb with. I still prefer a granny 4speed for offroading though.
For an off-road vehicle, I would think an auto could be better because of the torque converter cushioning the jolts, as you stated, and no clutch wear issues from feathering the clutch. Most rock crawlers prefer an automatic and super low transfer case and axle gears, sometimes using 2 transfer cases for a double-low ratio. The auto is easier to crawl and climb with. I still prefer a granny 4speed for offroading though.
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From: Chatsworth, CA
Originally Posted by tmorris1
How come most vehicles with automatics are rated to tow more than a manual tranny then?
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From: USA
T-morris is right, at least from a durability standpoint.
The benefit of the manual trans for towing is you have complete control of where in the rpm range your engine is operating for any given vehicle speed and you typically have more gears available in the manual, thus with less spread between each gear and the ability to keep the engine tightly in it's peak torque range with less bogging after shifting into the next higher gear.
Also there is the benefit of downshifting for greater engine braking when descending hills with a load behind you. Oftentimes the auto trans' next lowest gear is too low and some autos' torque converters will unlock below a certain speed, leaving you with no engine braking below that speed.
There are other reasons too, I'm sure, why nearly all big rigs are manual instead of auto and even most medium duty trucks too.
I know, I kind of got the whole discussion off-course by injecting towing into the mix. Sorry.
The benefit of the manual trans for towing is you have complete control of where in the rpm range your engine is operating for any given vehicle speed and you typically have more gears available in the manual, thus with less spread between each gear and the ability to keep the engine tightly in it's peak torque range with less bogging after shifting into the next higher gear.
Also there is the benefit of downshifting for greater engine braking when descending hills with a load behind you. Oftentimes the auto trans' next lowest gear is too low and some autos' torque converters will unlock below a certain speed, leaving you with no engine braking below that speed.
There are other reasons too, I'm sure, why nearly all big rigs are manual instead of auto and even most medium duty trucks too.
I know, I kind of got the whole discussion off-course by injecting towing into the mix. Sorry.
Posting Guru
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From: Copley, OH
The reason that manual tranny trucks have lower tow ratings is because Ford uses a POS weak manual tranny with the wrong ratios and equipped with an equally undersized clutch in the F150. Put in a ZF, or for that matter a T18/T19/NP435 and a HD clutch and you'll have all the towing capacity of a slushbox with twice the control.
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Post Fiend
Joined: Jun 2002
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From: Atlanta GA
> why nearly all big rigs are manual instead of auto and even most medium
> duty trucks too.
Unit cost and mileage cost.
$8,000-$12,000 extra for an automatic, plus, the higher upkeep makes it a bad choice. Especially if it is other other then in the city driving because the lower mileage would be a real killer where a few cents a mile is all the profit there is.
You can get auto trannies in a medium duty truck and a heavy duty truck, though they are usually only for in the city driving at rental places. I believe Freightliner offers automatics in their FL-80 (probably for motorhomes) though I have never seen them.
I think an automatic would be easier over the life of an engine, though is it going to yield any measurable gain? Most gas engines are history at 200k. I think it is like debating if tailgates up or down save on gas mileage. It might, but, can you really measure it and will it make any difference after 100,000 miles.
> duty trucks too.
Unit cost and mileage cost.
$8,000-$12,000 extra for an automatic, plus, the higher upkeep makes it a bad choice. Especially if it is other other then in the city driving because the lower mileage would be a real killer where a few cents a mile is all the profit there is.
You can get auto trannies in a medium duty truck and a heavy duty truck, though they are usually only for in the city driving at rental places. I believe Freightliner offers automatics in their FL-80 (probably for motorhomes) though I have never seen them.
I think an automatic would be easier over the life of an engine, though is it going to yield any measurable gain? Most gas engines are history at 200k. I think it is like debating if tailgates up or down save on gas mileage. It might, but, can you really measure it and will it make any difference after 100,000 miles.
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Post Fiend
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From: Metro Detroit (Redford)
Originally Posted by StrangeRanger
The reason that manual tranny trucks have lower tow ratings is because Ford uses a POS weak manual tranny with the wrong ratios and equipped with an equally undersized clutch in the F150. Put in a ZF, or for that matter a T18/T19/NP435 and a HD clutch and you'll have all the towing capacity of a slushbox with twice the control.
I would add one other reason the automatics usually are rated for more. The auto company knows most folks can't driver a clutch properly and are afraid they will burn up clutches. They don't want the warranty work and so a lower load rating will ensure fewer burnt clutches.