But I specifically mentioned knock. However, I find the auto knock detector and timing retard works effectively. I can lug car at speed that it doesn't accelerate (just did it for a quick test) and car still does not knock, even on regular. If anyone's car DOES knock, downshift and wait till higher rpm to shift.
Yes. I was agreeing with what you said and adding to it ( the oil pump comment).
-jim
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Over drive means a gear where the ratio through the transmission represents an increase in RPM, i.e. 0.75:1, and really has nothing to do with the ultimate drive train ratio.
Yup and most 5th or top gears are actually overdrive and the owners manuals even call them that. I know, I know, nobody RTFM these days, but I still do. They just aren't marked on the stick.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 'New' frame in the works for '08. Some Canadian Bush Trip and Build Photos:99% of those "5" speed manuals have the 5th gear as an OD gear. Some even have 4 and 5 as OD. The 85-86 and up automatics use a few tricks as well. Once you hit the 90s the old "manuals ALWAYS get better mileage" argument was no longer true. With many of the modern automatics you would have to be constantly shifting to match the control and mileage. Take a look at even the lowly 4L60E used in many GM RWD applications and its mate the 4T60E used in FWD vehicles. They both use locking torque converters, automatic overdrive, higher overall gear ratios than are possible with manuals and in general get the same or better mileage as well. With the latest generation of transmissions with 5,6 or more speeds, the manual trans is heading downhill fast.
Control? With an automatic? I think not. When an automatic no longer has the 2 second leg before it actually does something, has useable compression braking and reads my mind on when it should be shifting, I might consider one.
And is poor design. For fuel efficiency you want the least amount of gear train possible. Where do you want the most fuel efficiency? Top gear.
"Steve W." wrote in news:gcgfuj$1hu$ snipped-for-privacy@aioe.org:
so please name one model that has better milage with a auto than a manual. even with a lockup converter in the auoto he manual still has less friction loss. KB
But since there is a gear between the transmission and the axle, there is no physical reason why the axle in a front drive car should turn at the same speed as the mainshaft of the transmission.
In a rear drive car (most, anyway except for rare cars with transmission built into rear axle) the input to the rear axle turns at same speed as transmission mainshaft. An overdrive was a seperate gear set interposed between the transmission and the driveshaft. There is already such a gear in a front wheel drive setup.
Axle, not driveshaft, since there isn't one. Again, it's a function of the transmissions ratio, not the total driveline ratio. If the transmission has a gear where the output RPM is higher than the input RPM it's an overdrive gear.
Whether the transmission and differential are in the same physical housing or not makes no difference to the overdrive question.
No, that was a "gear splitting" secondary transmission which provided over and under drive ranges for each gear of the main transmission. Sometimes this was provided in the form of a two speed axle unit.
Nope, there isn't since it is a fixed gear, and it isn't an overdrive either since it is never turning the differential at a higher RPM than the transmission output.
Some of the (bogus) EPA MPG estimates claim better MPG on the auto version, based I suppose on invalid test procedures that assume an incompetent driver on the manual.
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