3.73 to 3.31 PCM problems

[Frenetic74]

2016 GT w/PP and Roush SC/ 6speed

I switched out the differential R&P to a 3.31 in order to better handle the power and give me more gear.

I’m experiencing intermittent limp mode now and am looking for a solution. Previous forum threads seem inconclusive about how to fix the problem. Hand held tuner, FORScan, Ford Racing’s ProCal.

Can anyone confirm if FORScan can reprogram the PCM or offer any advice on best way to go about this?

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[MRGTX]

Sheesh...even a 2016 having problems? Looks like final drive ratio swaps are trickier than most of us assumed they would be.

I’m having an issue with my 2020. Kind forum member @Superspirit posted this regarding FORScan. I have yet to use it myself (cable is coming this week) so I’m not sure how helpful this will be for you.

Forscan Rear Axle Ratio (3.15) BCM 726-12-01 : 013B xxxx xxxx Enable Rear Axle Ratio (3.31) BCM 726-12-01 : 014B xxxx xxxx Enable Rear Axle Ratio (3.55) BCM 726-12-01 : 0163 xxxx xxxx Enable Rear Axle Ratio (3.73) BCM 726-12-01 : 0175 xxxx xxxx Enable Rear Axle Ratio (4.10) BCM 726-12-01 : 019A xxxx xxxx Enable
...

EDIT: I believe the Roush tune specifies the final drive ratio, no? That might be where you need to start.

 

[Frenetic74]

Sheesh...even a 2016 having problems? Looks like final drive ratio swaps are trickier than most of us assumed they would be.

I’m having an issue with my 2020. Kind forum member @Superspirit posted this regarding FORScan. I have yet to use it myself (cable is coming this week) so I’m not sure how helpful this will be for you.



EDIT: I believe the Roush tune specifies the final drive ratio, no? That might be where you need to start.

Yeah, thanks for responding. I saw that post earlier and purchased a FORScan cable off amazon. It arrives tomorrow so I’m going to give it a shot. FORScan is free, so why not. I have a custom tune, not the canned Roush one, so I’m out of luck there. The Roush tune was only good if everything else on the car was stock. I’m running BBK headers, Magnaflow exhaust, so custom was necessary. The only thing stock in the car is the block. These are the prices you pay for customization I guess.

In case your curious. Drivetrain is Centerforce DYAD DS clutch, Calimer Stage-3 MT-82 Transmission, MGW shifter, Steeda aluminum single piece DS w/safety loop, rebuilt torsion differential with 3.31 R&P and GT350 half shafts.

 

[Superspirit]

Yeah, thanks for responding. I saw that post earlier and purchased a FORScan cable off amazon. It arrives tomorrow so I’m going to give it a shot. FORScan is free, so why not. I have a custom tune, not the canned Roush one, so I’m out of luck there. The Roush tune was only good if everything else on the car was stock. I’m running BBK headers, Magnaflow exhaust, so custom was necessary. The only thing stock in the car is the block. These are the prices you pay for customization I guess.

In case your curious. Drivetrain is Centerforce DYAD DS clutch, Calimer Stage-3 MT-82 Transmission, MGW shifter, Steeda aluminum single piece DS w/safety loop, rebuilt torsion differential with 3.31 R&P and GT350 half shafts.

I have read of two other cases with an aftermarket tune, both had to get an update from the tuner to fix the problems. I don't know for a fact that forscan will fix it, I just posted the codes other's have listed. I have successfully made other changes with forscan. But have not changed the gear ratio yet.

By the way, nice build list!

 

[Frenetic74]

I have read of two other cases with an aftermarket tune, both had to get an update from the tuner to fix the problems. I don't know for a fact that forscan will fix it, I just posted the codes other's have listed. I have successfully made other changes with forscan. But have not changed the gear ratio yet.

By the way, nice build list!

Thanks man! I guess I’ll just have to try the FORScan route and see if that works. Frustrating.

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