So the speed is either taken from the front wheels or after the pumpkin? Maybe I'll take a glance at the service manual and see if I can find it there.

 

The speedometer and tach won't be affected, but if you have an auto, the chances are you'll loose the use of your cruise control.

 

I'm having a hard time finding out anything from the service manual.

I do realise that the Tach won't be affected. But I can't find any cartainty that the speedo and Odometer won't be.

I don't see why someone would loose the cruise control.

 

I've run 23" drag radials which effectively gave me a 3.55 gear ratio at the track. The tach and speedometer all worked fine and weren't off. The speedometer read tire speed from the rear abs sensor and the tach picks up information from the driveshaft. The odometer won't be affected.

As for cruise control, numerous 5AT G owners that have done the 3.54+ gear swap have lost cruise control. The issue is that the ECU won't let you set cruise control if the rpms are above 3500rpms in 5th gear (~90mph). Since the deeper gears increase 5th gear rpm, the cruise control will not work because it thinks you're trying to set the cruise above 90mph.

 

Ahh yes thats what I'm looking for. Thanks for the info.

 

The reason the speedometer / odometer isn't affected is because the sensor comes from the rear wheel sensors. So if you adjust the rolling diameter of the tires, you will affect its accuracy. The final drive gear ratio doesn't change the amount of times a tire rotates in a mile, that is why its unaffected.

No. The cruise control system takes signals from both the rear wheel speed and the transmission rotational speed. The ECU expects the transmission to be rotating at a certain speed for any given gear at any given wheel speed. Because the final drive changes how fast the transmission rotates for a given wheel speed, it can push it outside its expected range of parameters, throwing code P1574. When that code is tripped, cruise control will not activate.

This is why some people with the 5AT who go to the 3.538 don't necessarily lose cruise control, or only at higher speeds. Also why people with the 6MT that swap final drives can lose it only in 6th gear.

 

Did one hell of a write up, and **** load of research! I was wondering i have the 5AT as well and was thinking about doing this mod, but its my daily driver and most of my driving is done on the freeway. If you are cruising at 80MPH what are your RPMS at roughly?

-sean

 

I guess I need to check my CC... I have 3.692 FD and CC has worked since install (over a yr now I think)... but today I checked for codes with Cipher and had P1574 (vehicle speed sensor)... maybe my CC isnt working now? The only recent change has been cams and headers (and new tune).

 

I have a 6mt with 4.08 gears...

3400 rpm is 80 miles an hour...

My CC works up to 85 miles an hour...

 

what is the stock final gear ratio for the 5AT '04 coupe? What is the correct ratio that should be used when using a dynapak dyno?????

 

5AT has a 1:1 gear ration in 4th gear

FD is 3.3

 

4th is 1:1 - however, on a Dynapack, 3rd has been found to be more consistent and accurate (only debated by those that have no clue).

So 3rd which is 1.47:1 would be the proper gear to dyno in on a Dynapack (to answer Gee Wiz' question - oh, and 3.357 is FD).