magnum XL trans/rear end 3.31- speedo is off

[Keith 5.0]

I just bought a 2012 GT from a member on here that has a magnum XL trans and a 3.31 rear end. The car has a SCT tune on it but when I look up the gearing that's programmed through the tuner, it's showing stock. How do I account for the transmission gearing being different rather than the rear end being different? With anything over 80 mph being considered reckless driving in VA, I'd like to be sure of how fast I'm going.

Thanks!

 

[BigPoppa]

You can't make adjustments in the ECU to accommodate the trans, so it should have the stock gearing configured.

Magnum swaps on 2011+ cars require a speed calibration box to convert the speed signals.

Your car should already have it if the install was done correctly. The box should be in the vehicle interior as it isn't weather proof. A lot of guys just locate it under the dash, in the glove box, or under the center console.

If you don't have one, JPC sells them on their website, as well as several other Magnum swap kit vendors.

 

[stang910]

Not true, it can be corrected in the tune. Just gotta find someone willing to make the changes.

 

[BigPoppa]

Not true, it can be corrected in the tune. Just gotta find someone willing to make the changes.

That's interesting.

How do you tune it to convert the two wire signal from the T-56 sensor used on the Magnum to the three wire signal the 2011+ ECU requires?

 

[stang910]

Not sure how wire it since i didn't do the install, but had a car come to me with a magnum swap and he said the speedo was way off. Asked him a few questions and turned out the speedo was working correctly without a conversion box just was way off and his cruise didn't work. I made the correct changes in the tune and he's never said another word about the speedo or the cruise.

Obviously the OP has wired his up to work also so now he just needs the correct adjustments in the tune.

 

[BigPoppa]

I see. Seems like someone just swapped the connector for the 2-wire instead of using a cal box.

The T-56 is typically 17 pulses per revolution and the MT-82 is something like 40.

Changing the VSS P./Rev - Trans from 40 to 17 should work then.

N/V shouldn't need to be changed since it is a manual trans.