Hi I was wondering what is the rpm on an ap2 with 4.56 gears when you're going 75mph....also does the extra rpm only show before or after the yellow box install?

 

We should make this a sticky somewhere

-------------->>>>>>>>>>>>>>>ZERO TURN


RPMs do not change with or without the yellobox. You're engine is turning xyz and that's what you see on the tach. The YB corrects the Speedo.

EDIT:

4000 RPM = 75.5 MPH (in 6th gear with an AP2 with 4.1)

4450 rpms = 75.5 (with 4.56) So you pick up 450 rpms with the 4.56 at 75 mph.

 

I seen that gear calculator a couple of times now but never understood it....but now finally figured it out, thanks for the quick answer......

 

Sorry I messed up the first time. I didn't put the 4.56 in the gear ratio, so 4000 rpms = 75.5 mph with stock gears)

WITH 4.56 4000 rpms = 67.9 MPH


With the gear calculator you can change the gear or the rpms to see what speed you should be going when in a certain gear.

 

hmm thats weird as I just got my gear changed and I'm still at 4k rpm at 75mph...but let me go take another test drive and make sure.......

 

Do you have a Yellow Box (or equivalent) and is it calibrated correctly? Without a speedo correction device, your speedo and rpm will remain exactly the same as it did before the gears went in.

 

yes its confirmed I am at 4k rpm when I'm at 75mph....maybe my speedo is off due to not installing the yellow box yet and it is really 65mph, anyone has any insight on this?

 

[QUOTE=xviper,Dec 24 2005, 04:38 PM] Do you have a Yellow Box (or equivalent) and is it calibrated correctly?

 

If you have 4.56's your speedometer is ahead about 11% give or take a percent so you're not really doing 75...probably more like 67 or so.

 

I think you really need to read up and understand exactly what these gears do and how they work and how it affects your car. You don't seem to have any understanding about this.
You have changed the mechanical advantage of your drivetrain. Because the speedometer pickup is BEFORE the final drive gears (which you changed), ONLY the speedometer (and odometer) readings have been affected such that they need to be corrected. Your redline has NOT changed nor has your fuel cut.

This is what we've been trying to tell you all along. This is a concept that you have not understood. Changing final drive gears changes the speed that the car is going at the same rpm. This is why you need a Yellow Box - so you can correct the speedometer signal.
The percentage (%) increase in mechanical advantage that the gears provide you is also the same % error that your speedo now has. You will rack up mileage this same % more than it really does.