4.09 gears help

[Krusin5.0]

Hello everyone,

I have a little issue with my 2015 gt premium. Has normal bolt ons.
Long tube headers
Cat delete
Off road x pipe
Borla atak mufflers.
JLT cold air intake

I recently changed the rear end gears from 3.31 to 4.09’s. I have an SCT BDX tuner and was told that I could change the gear ratio. Said ok simple enough, ordered the gears and had them installed. When I picked up the car, I updated the gear ratio and tire size. I left the parking lot and it didn’t feel right at all. Lacking a lot of power. Took it very easy the next couple of drives breaking them in keeping city speeds. Here come the day that I get to up the speed a little, the car went into limp mode. Gas pedal none responsive etc. pull the code and I have a PO422 and a few others which lead me to replacing the throttle body. The 422 error is the BCM freaking out over the new gears. Took it for another drive and again limp mode in the higher gears.

did some research and was wondering if someone could give me confirmation.
I thought that the hand held tuner was enough to change the gear ratio but appears that’s only 1/2 the work required.

I have found that I need a Whipple flare tool to update the BCM cause my car only has the options from the factory for 3.15, 3.31, 3.55 and 3.73 gears and with the 4.09 gears, it’s freaking out. Dealer is unable to update as their tools do not give them access to do it they say.

can this be done with forscan as well or is my only option is to use the Whipple? In forscan my gear options are limited to 3.77. Can I change that limit in forscan or is Whipple the only way? If anyone knows how to update via forscan, I would really appreciate the assistance.

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[K4fxd]

Your tuner should be able to update it in the tune. He needs to change ECM 845 to something higher than 4.09
Needs to change ECM 9050 to 4.09
Might need to change ECM 2849 to calibration

These ECM numbers are in HP tuners format. SCT might be different.

 

[Krusin5.0]

From my understanding, tuners cannot change the BCM settings. Will shoot them a message and see their response.

 

[K4fxd]

ECM 2849 takes the BCM out of the equation. (BCM switch)

The FRPP tunes just change the tables I listed, without changing the BCM switch

 

[junits15]

ECM 2849 takes the BCM out of the equation. (BCM switch)

The FRPP tunes just change the tables I listed, without changing the BCM switch

Does the BCM use the ratio for anything? If we force the ECM to a higher ratio like you showed, and leave the BCM as is(stock), is there any issue caused by that?

I'm thinking about 4.56 in the future and I've heard rumors here and there that the BCM can't go above 4.10, was wondering if you knew anything about that.

 

[K4fxd]

Max in the ECU is 64 to 1.

I never tried a 4.56. If the BCM is maxed at 4.10 I would assume you would have to use the calibration setting on the BCM switch.

As far as any issues, I could see some problems with rev matching.

One of these days when I have some time I'll force mine to use calibration and let you know if anything funky happens.

 

[K4fxd]

I did find time to try forscan. My car accepts 4.56 in the BCM.

I'll try to fine time today or tonight to try the BCM switch in the PCM tune.

 

[Krusin5.0]

Talked to my tuner and communication is below. They cannot make the adjustments.


I just had the 4.09 gears changed in the car and it is going into limp mode.

Said no problem, must be due to not updating my can tune to account for the new gears. Updated the tune and took it for another drive and again limp mode. The tune is only changing the ecu settings and the BCM is freaking out and causing limp mode.

From my research, I have found out that my car only has the options for 3.15, 3.31, 3.55 and 3.73 gears and the 4.09 gears are an option through Ford Performance. So the data supplied by the sensor is out of range causing limp mode.

I contacted SCT to see if they could help. They said that I would need to purchase a Whipple tool so I could update the BCM to accept the new gear ratio as they could not make the proper calibration through a tune only.

Is this something u can tune for or is my only option is to get the whipple tool?

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I talked to our tuner and he said that he does not make the change in tune for gears that the car will figure it out. Don’t know how it works but we suggest reloading the tune and NOT change the gear ratio and see what happens.

He said when he makes changes that the car doesn’t really go into limp mode, but the computer will de-rate the throttle to like 1/4 and sets a strange speed limiter.

I have not heard of the whipple tool I am sorry. So give it a shot by not making a change. Let me know if it works

———————————————————————

The problem is the car will figure it out on its own if the gears are 3.31, 355 or 373 as the BCM has data for those parameters. The 4.09’s it does not so needs to be injected into the BCM. Once the data is there, it will auto calculate. Loaded the tune a few times now and always a problem.

The Whipple tool will allow me to add these parameters. Thought tuners could turn off the BCM check from the ecu to bypass this requirement.

—————————————————————


We can not do a tune for gears at all on these cars so our tune file would not help.

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So I guess that I need the Whipple tool or figure out how to enter the new data via forscan if it’s even capable?

 

[StangTime]

Find somebody you can borrow a Procal4 device from. You can use it to program your gear change and give it back to them.

Just noticed you're in Canada. Where?

 

[Krusin5.0]

Procal tool is only able to adjust up to 3.73’s as it does the same as any tune. The BCM is still untouched.

Located in Amherst Nova Scotia.

 

[K4fxd]

Gear ratios in 726-12-01 are the hex value for the digits:
3.15 = 13B
3.31 = 14B
3.55 = 163
3.73 = 175
4.10 = 19A
4.56= 1C8

Use forscan.

I'd call another tuner that uses SCT and ask them about 4.09 gears.

 

[StangTime]

Procal tool is only able to adjust up to 3.73’s as it does the same as any tune. The BCM is still untouched.

Located in Amherst Nova Scotia.

Procal4 does do up to 4.09 gears. Maybe the old ones don't.

 

[K4fxd]

OP

Who is your tuner? Is it the SCT canned tune's?

 

[Krusin5.0]

Tried both the canned tune from Brenspeed and a custom tune, even removed my cold air intake and flashed back to stock.

emailed a few others and waiting for a response.

 

[K4fxd]

This is the first time I have heard of anyone having trouble with a second gen.

Keep us posted

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