are any of the higher speeds overdrive?
cars with 7 or 8 speeds
- Thread starter edwardh1
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If you mean ratios below 1, then in my Charger gears 7 and 8 are overdrive. Same on wife's Q5. They both have ZF units.
I'd bet that at least 1 gear in every modern automobile is overdrive.
Originally Posted By: MCompact
The 8HP45 in my 2 Series has the identical gear ratios; the final drive ratio is 3.08
Yeah, it appears all the 8HP units have the same gear ratios. The Q5 has 8HP55. The SRT has 8HP70.
The 8HP45 in my 2 Series has the identical gear ratios; the final drive ratio is 3.08
Yeah, it appears all the 8HP units have the same gear ratios. The Q5 has 8HP55. The SRT has 8HP70.
Originally Posted By: Quattro Pete
If you mean ratios below 1, then in my Charger gears 7 and 8 are overdrive. Same on wife's Q5. They both have ZF units.
They both have ZF's, but people still rip on them for having Chrysler transmissions? LOL
Politics at it's finest.
If you mean ratios below 1, then in my Charger gears 7 and 8 are overdrive. Same on wife's Q5. They both have ZF units.
They both have ZF's, but people still rip on them for having Chrysler transmissions? LOL
Politics at it's finest.
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Originally Posted By: dlundblad
They both have ZF's, but people still rip on them for having Chrysler transmissions? LOL
Politics at it's finest.
Charger SRT has a ZF trans made by ZF.
The regular Charger V6 has a Chrysler made trans based on a ZF design (845RE).
Not sure who's ripping on what, but the biggest thing with these transmissions is the programming which I believe each auto manufacturer is responsible for, not ZF. Chrysler's programming isn't as buttoned up as BMW's or Audi's programming.
They both have ZF's, but people still rip on them for having Chrysler transmissions? LOL
Politics at it's finest.
Charger SRT has a ZF trans made by ZF.
The regular Charger V6 has a Chrysler made trans based on a ZF design (845RE).
Not sure who's ripping on what, but the biggest thing with these transmissions is the programming which I believe each auto manufacturer is responsible for, not ZF. Chrysler's programming isn't as buttoned up as BMW's or Audi's programming.
FYI, found gear ratios for a ZF 9-speed trans that appears to have 4 overdrive gears:
https://www.allpar.com/mopar/transmissions/ZF9.html
https://www.allpar.com/mopar/transmissions/ZF9.html
"Overdrive" was a meaningful term way back when most cars were rear-drive with a direct 1:1 top gear. Then the overall ratio was the same as the "rear end" (final drive) ratio, unless you had the optional overdrive. Nowadays, it doesn't mean much. The overall ratio still matters, but whether it is achieved with with an "overdrive" transmission ratio ahead of the final drive is of no particular significance. Thus, 0.6×4.0 should perform about the same as 0.8×3.0 or 1.0×2.4.
Originally Posted By: benjy
i prefer to decide what gear an when to shift
You can do that with many automatics these days.
i prefer to decide what gear an when to shift
You can do that with many automatics these days.
seems to me, any underdrive or over drive ratio is more lossy than direct drive. But only fractionally so.
Ultimately it's all about cruise rpm. And hill climbing rpm. As much as it bothers me, all cars should downshift on a hill. Otherwise it means that the engine is spinning too fast on the flats, let alone downhill. Most differentials run some amount of underdrive, so overdrive in the transmission is required. But who cares, it's the overall ratio that matters.
Ultimately it's all about cruise rpm. And hill climbing rpm. As much as it bothers me, all cars should downshift on a hill. Otherwise it means that the engine is spinning too fast on the flats, let alone downhill. Most differentials run some amount of underdrive, so overdrive in the transmission is required. But who cares, it's the overall ratio that matters.
Originally Posted By: supton
As much as it bothers me, all cars should downshift on a hill. Otherwise it means that the engine is spinning too fast on the flats
what about larger displacement v8's that have ample tq and hp that it doesn't need to downshift?
I've rented 300c's with the 5.7 hemi, and while going up mountain passes with the cruise on, it never needed to downshift to maintain speed while at a low rpm.
As much as it bothers me, all cars should downshift on a hill. Otherwise it means that the engine is spinning too fast on the flats
what about larger displacement v8's that have ample tq and hp that it doesn't need to downshift?
I've rented 300c's with the 5.7 hemi, and while going up mountain passes with the cruise on, it never needed to downshift to maintain speed while at a low rpm.
Originally Posted By: supton
... Ultimately it's all about cruise rpm. And hill climbing rpm. As much as it bothers me, all cars should downshift on a hill. Otherwise it means that the engine is spinning too fast on the flats, let alone downhill. ...
True in principle, but obviously not well understood. As a practical matter, manuals and step-shift automatics have to be geared to allow climbing modest grades (or equivalent acceleration) without downshifting, to minimize wear and nuisance of excessively frequent shifting. How steep a grade can be climbed without downshifting is a compromise the manufacturer must make. My Mazda 5-speed (below) had a better compromise than many manual cars.
... Ultimately it's all about cruise rpm. And hill climbing rpm. As much as it bothers me, all cars should downshift on a hill. Otherwise it means that the engine is spinning too fast on the flats, let alone downhill. ...
True in principle, but obviously not well understood. As a practical matter, manuals and step-shift automatics have to be geared to allow climbing modest grades (or equivalent acceleration) without downshifting, to minimize wear and nuisance of excessively frequent shifting. How steep a grade can be climbed without downshifting is a compromise the manufacturer must make. My Mazda 5-speed (below) had a better compromise than many manual cars.
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My wife's jeep with a 9 speed
5th - 1.00
6th - 0.81
7th - 0.70
8th - 0.58
9th - 0.48
although it NEVER uses 9th...or 1st for that matter.
5th - 1.00
6th - 0.81
7th - 0.70
8th - 0.58
9th - 0.48
although it NEVER uses 9th...or 1st for that matter.
Originally Posted By: DriveHard
although it NEVER uses 9th...or 1st for that matter.
Why is that?
I can understand 1st gear not being used if you're in some "ECO" mode, and 9th not being used if in some sort of "SPORT" mode, but both 1st and 9th not being used as part of the same program?
Maybe you're not going fast enough?
although it NEVER uses 9th...or 1st for that matter.
Why is that?
I can understand 1st gear not being used if you're in some "ECO" mode, and 9th not being used if in some sort of "SPORT" mode, but both 1st and 9th not being used as part of the same program?
Maybe you're not going fast enough?
Originally Posted By: Quattro Pete
Originally Posted By: DriveHard
although it NEVER uses 9th...or 1st for that matter.
Why is that?
I can understand 1st gear not being used if you're in some "ECO" mode, and 9th not being used if in some sort of "SPORT" mode, but both 1st and 9th not being used as part of the same program?
Maybe you're not going fast enough?
It always starts in second unless you switch to manual mode and put it in first...which I do on occasion to get away from a light more quickly. It will also select first if you chose "4-low". It doesn't really have a transfer case or low gear...it just selects first which is not normally available.
Even at 80 mph it won't shift into 9th. If you select manual and shift it into 9th with the cruise control on, you can actually watch the mpg drop...even on flat, level road with little to no wind. As soon as you switch back to auto mode it will pop back down into 8th.
Originally Posted By: DriveHard
although it NEVER uses 9th...or 1st for that matter.
Why is that?
I can understand 1st gear not being used if you're in some "ECO" mode, and 9th not being used if in some sort of "SPORT" mode, but both 1st and 9th not being used as part of the same program?
Maybe you're not going fast enough?
It always starts in second unless you switch to manual mode and put it in first...which I do on occasion to get away from a light more quickly. It will also select first if you chose "4-low". It doesn't really have a transfer case or low gear...it just selects first which is not normally available.
Even at 80 mph it won't shift into 9th. If you select manual and shift it into 9th with the cruise control on, you can actually watch the mpg drop...even on flat, level road with little to no wind. As soon as you switch back to auto mode it will pop back down into 8th.
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