i'd like to switch just my 5th gear, which is 0.83, for one around .7 (5 A/T 03 coupe). has anyone done this?

is it possible to change just the 5th gear?where can i find one?

Gear Type5 Speed Automatic w/ Manual Shift ModeFinal Drive3.36:11st Gear Ratio3.54:12nd Gear Ratio2.26:13rd Gear Ratio1.47:14th Gear Ratio1.00:15th Gear Ratio0.83:1

The top gear is selected to allow the fully loaded vehicle to go up a mild incline AC in 100F weather with minimal lugging at low speed.

Redesigning an AT is significant design effort [not just gears but tcu reprogram] much easier and less expensive to swap rear diff ratio downward by the 15%.............total acceleration would only decline by cube root or ~~ 2.5%...............0.3-0.4 secs in quarter mile.

Seem to remember the early 2002-03 Q45 had a 3.133[?] diff gear...........6% reduction in engine speed vs rpm. Couple that with larger diameter rear tires and you might get a 10% reduction in rpm and a 10% [?] saving in MPG.

Q45tech wrote:Redesigning an AT is significant design effort [not just gears but tcu reprogram] much easier and less expensive to swap rear diff ratio downward by the 15%.

i want to keep acceleration where it is, so i'm not willing to change the rear diff ratio.

my objective is to reduce RPM when cruising at 95+ mph. i always downshift to 4th when accelerating on the highway. replacing just the 5th gear would be the perfect fix if it doesn't take too much effort/$... would you mind telling me a bit more about what this would entail? thanks!!

As Dennis said, it's just not that simple. Manual transmissions are simpler in design. Each pair of gears in a manual transmission is meshed together constantly between two shafts. One shaft has gears fixed to it. The other allow the gears to spin freely on them. This shaft has dogs that are fixed to the shaft that engage the selected gear and lock that gear to the shaft. To change a gear ratio, you can simply switch only the gear you wan t to the desired ratio you want.

Auto trannies use an entirely different set-up. This would require a more elaborate explanation, but check out this site for more details:

http://auto.howstuffworks.com/...3.htm

As you can see from the site changing the gears will require much more work, more parts and will change other gear ratios along with it. To get what you want out of it, it will require to essentially redesign it.

Custom design a auxillary external 2 speed gear set between AT tranny and rear diff - cut down drive shaft electric clutch..........shouldn't cost more than $10,000 to get it reliable to save how much in gasoline or engine wear?

Wait a few years and see if JATCO redesigns the internal gear set span ratio or adds a 6 speed AT that might bolt up with new harness and tcu from a junk yard.

The old 4 speed AT had a 2.784/0.694=4.01 span your 5 speed has a 3.54/0.83=4.265 span.....................the 4th gear in the old 4AT was a 0.694