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Overdrive

  #1  
Old 07-11-2006, 04:35 PM
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Default Overdrive

I'm looking at the Honda Fit & Toyota Yaris and was wondering -- what is 4-speed electronically controlled automatic overdrive?
 

Last edited by Jason; 07-11-2006 at 04:37 PM.
  #2  
Old 07-11-2006, 06:14 PM
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Default Re: Overdrive

a gear that the car goes into when the crankshaft is spinning faster than the engine, correct me if I'm wrong. Usually there's a button next to the auto tranny to disable or enable OD(usually its on by default), just so if you need that extra passing power you can disable the OD.

Then turn it on OD again when you want to save gas, once your crusing at a set speed the car will kick into overdrive and the engine spins less.

For us manny trannies, our overdrive is our "5th" gear.
 
  #3  
Old 07-11-2006, 07:02 PM
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Default Re: Overdrive

Is this kinda like a regular 3-speed automatic transmissions 4th "highway" gear or mode?

For instance years ago I bought a used Oldsmobile. From a stop you could feel it shifting to 2nd, then 3rd. A bit more speed dropped it essentially into a "4th".

Later it developed transmission trouble where the torque converter "lockout" solonoid would stick. Symptoms were the transmission would not disengage from the engine while stopping, so like a clutch car stopping without depressing the clutch....the brakes would drag the engine to a stop.

Apparently this lockout solonoid bypassed the torque converter for 1:1 engine-transmission ratio.

Since the car was on its last legs I unplugged that lockout solonoid which fixed the brakes from stopping the engine.
But caused another issue that it wouldn't go into that highway "4th" (so to say).
Without that solonoid working MPG's went really bad out on the open road.

I'm sure Honda's are OK but heard it is a common (But expensive to fix) GM issue.
 

Last edited by Hot_Georgia_2004; 07-11-2006 at 07:04 PM.
  #4  
Old 07-12-2006, 03:36 AM
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Default Re: Overdrive

For that matter, what the heck is a "manumatic" and an "automated manual"?
 
  #5  
Old 07-12-2006, 05:07 AM
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Default Re: Overdrive

Like phil said, "overdrive" just means a gear that allows the output shaft to spin faster than the input, improving fuel economy vs. a direct gear. I once had a Volvo with a really fun overdrive arrangement. They took a four-speed manual box and slapped what is essentially a small, two-speed automatic transmission on the back. What you had to do was shift through four gears, then push a button on the shift **** to engage the "fifth" gear. I liked it, but the thing was finicky.

Anyway..."manumatics" can take two forms. The most common is an automatic transmission that allows the driver to choose the gear (as long as the computer approves of the selection.) Generally speaking, those suck for anyone used to a real manual. Very sloppy, and usually quite a bit of lag between clicking the shifter and actually getting the gear change. The other form is a bonafide manual transmission where a computer takes over the clutch and shifter work. This is what people refer to when they talk about a "F1 transmission." The hip thing to do with these is put a set of paddles behind the steering wheel to control upshifts and down shifts. "F1" boxes are more desireable because the real clutch & gears results in positive lockup in all gears (more efficient than a torque convertor) and the gear changes tend to be a lot faster. Then there's VW's "direct shift" transmission, which supposedly has a manual shifting mode. Those are incredibly slick because you never actually lose the connection between engine and wheels during a gear change. Just don't ask me to explain the details of that one!
 
  #6  
Old 07-12-2006, 12:40 PM
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Default Re: Overdrive

Or, simply put, it's like 99% of all other 4 speed automatic transmissions. Everything sounds special once the marketing dept gets their hands on it.
 

Last edited by Droid13; 07-12-2006 at 12:42 PM.
  #7  
Old 07-14-2006, 01:08 PM
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Default Re: Overdrive

It's worth pointing out at this point the Fit has a 5-speed automatic, not 4.
 
  #8  
Old 07-14-2006, 01:16 PM
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Default Re: Overdrive

Originally Posted by AZCivic
It's worth pointing out at this point the Fit has a 5-speed automatic, not 4.
"Car & Driver" really liked the Fit's 5AT -- especially since it has paddle shifters for that manual-automatic experience.

I thought I read somewhere that some of GM's SUVs have 6 or 7 speed automatics.

Personally, I totally dig the CVT that propells my HCH. CVT is the best thing since sliced bread.
 
  #9  
Old 07-16-2006, 11:00 PM
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Default Re: Overdrive

I know the Chevy Corvette has a 6-speed automatic, and the Corvette's basic V8 is approximately shared through much of their SUV lineup. It wouldn't surprise me if the intention was to get the 6-speed in all their V8 vehicles. With the AFM system (cylinder deactivation) and a 6-speed automatic, they should have their SUV's up to where our regular sedans were about two decades ago. That is a good thing considering a mid-size SUV probably has two or three times the interior volume as my 1983 Maxima that got 16 to 22mpg or so when I owned it.
 

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