Thoughts guys...4.09:1 gears or the FRPP Power kit for my 2020 Mustang GT PP1 manual

[Marketplaza]

Ok cool. I'll PM you my cell #.

I paid 400 for the gears and installation kit( definitely get the kit) and 800 for install. You definitely need a tune going from 3.55 to 4.09, a ton of stuff stopped working until I got the tune. Everyone that says you don’t need a tune doesn’t drive a 18+.

I do notice a huge difference in pick up. At 45 I’m usually in 5th gear now. Not much of a difference honestly. But with a roush cai, e85 tune and now 4.09 my car pulls like crazy. I wouldn’t be surprised if I ran low 11s or high 10s.

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[JustDSM]

My problem was finally taken care of. It was the tune all along everything else was done correctly. I just don’t get why the Lund rep I talked to said it was the bdm not the pcm so it wasn’t the tunes issue. But I guess he doesn’t know what he’s talking about. But now that I can drive it normal it’s a totally different ride, I fish tailed in 3rd gear. The pick up now is amazing with the 4.09 gears. Btw do gears give you more torque or is it all about the rpms? But it’s really fun to drive it now.

The BDM is what has the gear ratio programmed, and the BCM feeds the ECU the "data". You can force the issue with the ECU and set it manually (what the tuners do). See below:

Stock 2020 Mustang GT PP1 configuration:

As you can see from above, the tire size and gear ratios are set to "Learn from BCM". The ECU has the inputs below to allow manual configuration, but in stock settings, they are all ignored as the "Learn from BCM" setting overrides these data points and pulls the calibration data from the BCM.

Setting the "Use Tire Circ." & "Use Final Ratio" to "Calibration" will enable the fields below allow you to manually configure your tire size and gear ratio's.

Above is from my personal 2020 PP1 GT w/ HPTuners.

 

[Rpinaiii]

^^^ I have the new Ford Performance Power Kit, it has the calibration tool you can hook up to the car, there is an option to change tire size and gear ratios up to 4.09. So I think that would also take care of any issues with the cars computer hopefully.

 

[Marketplaza]

^^^ I have the new Ford Performance Power Kit, it has the calibration tool you can hook up to the car, there is an option to change tire size and gear ratios up to 4.09. So I think that would also take care of any issues with the cars computer hopefully.

that would definitely work but at that point you might as well get a tune. I’d personally recommend Lund as there a lot better than Bama or sxt. I got the ngauge e85 tune and love it, I’ve now beaten scat packs and camaro ss. I can even fish tail in third gear with the 4.09 gears.

 

[AZ18yote]

that would definitely work but at that point you might as well get a tune. I’d personally recommend Lund as there a lot better than Bama or sxt. I got the ngauge e85 tune and love it, I’ve now beaten scat packs and camaro ss. I can even fish tail in third gear with the 4.09 gears.

To be fair can't call Bama or SCT tunes though lol. Gotta go with one to reputable tuners like you said Lund, AED or PBD.

 

[Marketplaza]

I’m curious, before I got the 4.09 gears I had 400 torque per the dyno. But that was with 3.55, how much more torque do you you think I have now? I really don’t want to have to get another dyno just to see.

 

[Dave2013M3]

I’m curious, before I got the 4.09 gears I had 400 torque per the dyno. But that was with 3.55, how much more torque do you you think I have now? I really don’t want to have to get another dyno just to see.

Its a mechanical torque multiplier, has nothing to do with the amount of torque the engine produces.

 

[Marketplaza]

Its a mechanical torque multiplier, has nothing to do with the amount of torque the engine produces.

I figured it added more torque cause it sure feels like it when I take off.

 

[Rpinaiii]

Anyone else do the 4.09 swap on 18+ GTs yet?

 

[Dave2013M3]

Maybe getting this done this month.

 

[ice445]

The BDM is what has the gear ratio programmed, and the BCM feeds the ECU the "data". You can force the issue with the ECU and set it manually (what the tuners do). See below:

Stock 2020 Mustang GT PP1 configuration:

As you can see from above, the tire size and gear ratios are set to "Learn from BCM". The ECU has the inputs below to allow manual configuration, but in stock settings, they are all ignored as the "Learn from BCM" setting overrides these data points and pulls the calibration data from the BCM.

Setting the "Use Tire Circ." & "Use Final Ratio" to "Calibration" will enable the fields below allow you to manually configure your tire size and gear ratio's.

Above is from my personal 2020 PP1 GT w/ HPTuners.

So does this mean you should be able to use ForScan to alter the BCM's "as built" data for the final drive ratio? Since that's likely what the factory is doing anyway if they don't want to have different ECU variations to account for the different builds. But I just want to confirm. Because if so, that's easy. Really easy. Then all you have to do is reset the KAM and the ECU should "learn" the new ratio. Is the "max" ratio a problem though? I see it tops at 3.79, which obviously isn't going to cut it for something shorter than that.

 

[Mikepol2]

What the gear change does is increase the force applied to the road by the rear tires:

Road force at a particular RPM in a particular transmission gear = torque x trans gear x diff gear / tire radius in feet.

So if we use the 18+ max torque of 420 ft-lbs in 4th gear, which has a 1:1 ratio, and use the diameter of my 305/35-19 rear tires, the force applied to the road with my stock 3.73’s was 420 x 1 x 3.73 / 1.1421 = 1,372 lbs. Changing the gears to 4.09’s increases the force to the road to 1,504 lbs. Working backwards, it’s the EQUIVALENT force applied to the road of a car with 3.73’s and 460 ft-lbs of torque.

And I made no tuning changes after the 4.09 installation and my car runs like a champ, no issues.

 

[Superspirit]

What the gear change does is increase the force applied to the road by the rear tires:

Road force at a particular RPM in a particular transmission gear = torque x trans gear x diff gear / tire radius in feet.

So if we use the 18+ max torque of 420 ft-lbs in 4th gear, which has a 1:1 ratio, and use the diameter of my 305/35-19 rear tires, the force applied to the road with my stock 3.73’s was 420 x 1 x 3.73 / 1.1421 = 1,372 lbs. Changing the gears to 4.09’s increases the force to the road to 1,504 lbs. Working backwards, it’s the EQUIVALENT force applied to the road of a car with 3.73’s and 460 ft-lbs of torque.

And I made no tuning changes after the 4.09 installation and my car runs like a champ, no issues.

Yet 3 other people have documented problems and have had to have a flash to restore proper operation.

 

[wtb6mtv8rwd]

If it's anything like other cars, the auto trans cars will need software tweaks but the manual will probably run fine without.

 

[Mikepol2]

Yet 3 other people have documented problems and have had to have a flash to restore proper operation.

I can’t speak for anyone else. All I know is my 2018 PP1 manual works fine, speedo is correct, drive modes work, no other weird issues or warning lights.

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