3.73 to 4.88 Gear Swap Problems **RESOLVED, STEEDA TUNE FIXED ALL ISSUES**

[Norm Peterson]

The next question I have is , does the 4.56 also spin wheels and in which gears?

I wouldn't count on there being any difference below 3rd gear. When shifting into 3rd or 4th it ought to be a little easier to avoid chirping the tires, though.

You'd still be pedaling it on any hero 0 to 60 run.

I also believe the area of the contact patch doesn't change. All you are doing is changing its orientation.

It's not quite that simple. Actual contact pressure is not uniform due to tire carcass stiffnesses, and it also varies with inflation pressure. That's before considering that tread grooves don't provide any tread contact with the pavement.

Going to wider tires also means that your wheels will get bigger increasing weight and rotational mass is not a good place to add it. That will slow you down too.

Maybe, maybe not. As long as you can spin the tires, rotational wheel effects aren't going to hurt you, and could possibly help.

No free lunch.

Engineering compromises tend to be like that.


Norm

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[Dave2013M3]

Quick, it's "priceless"

That was just a typo..

 

[L0566Bullitt]

Regarding traction in second, I think 4.56s would be perfect. With 4.88s, if I'm rolling and the engine is around say 4,000 rpm with traction control off and I mash the throttle, I'd say half the time (depending upon surface temperature and road type) the tires break loose and half the time they grip. So I can't help but think 4.56s would help maintain traction all the time, and help with 0 - 60. Love the 4.88s, but 4.56s may be better for most people.

 

[Fly2High]

Now, if you had PP2 setup with those 305/30R19 and a 4.09 final drive, you would effectively have a 4.32. That could be the best setup. Wide enough tire for the traction, suspension to handle it and enough gear to make even the MT-82D4 be really good.

As it is, getting a PP2 with a 3.73 is 0.2 seconds faster than a GT or PP1 GT because of the change in the effective final drive. Effectively it is already a 3.94.

For me with a PP2, I think the 4.09 would be tops. Anything more and I would just be spinning tires!! LOL

I wouldn't be surprised if the Mach 1 HP is also 0.2 seconds faster than the regular Mach 1 for the same reasons. I think a manual Mach 1 HP might be able to do 4.0 or slightly better. At least here is to hoping.

 

[Norm Peterson]

With 4.88s, if I'm rolling and the engine is around say 4,000 rpm with traction control off and I mash the accelerator, I'd say half the time (depending upon surface temperature and road type) the tires break loose and half the time they grip. So I can't help but think 4.56s would help maintain traction all the time, and help with 0 - 60.

What I think would really happen is that the tires would still break loose, just not quite as often as with 4.88s. You'd still have to pedal it a bit during a 0-60 run and be careful on the 1-2 upshift.



4000 rpm in 2nd sounds suspiciously like roll-racing from about 30 mph. If that's what I was going to be doing with my car, I'd start with something entirely different.


Norm

 

[L0566Bullitt]

There were some questions as to the MPG I'd get with these 4.88 gears. I reset my trip when I left home and around 3 hours/210 miles into the trip, hit exactly 24.0 MPG. Speed limits ranged from 55 - 70 MPH so my speed ranged from 64 - 79 MPH (2,600 - 2,900 RPM). I was hoping to get better than 24 and see maybe 24.1 but hit some mountains so by the time I arrived my final average was 23.8 MPG at 238 miles.

Pulling high vacuum/low load allows for a smaller fuel pulse which offsets the higher RPMs. I think the AFR is too rich at high vacuum/low loads and even better MPG could be achieved with a leaner AFR at high vacuum.

Cruising vacuum on the level

 

[GreenS550]

I was watching this thread a while ago and having owned a Bullitt I know how crummy the gearing is. 1 have always thought the 456 would be perfect.

I am close to ordering a 2021 Mach 1 where the gearing is similar to the Bullitt. Originally I was going to order it with the a 10, but in the meantime I bought an 18 and ProCharger it with the a 10. Now I'm looking to do the Mach 1 with the Tremec.

If it is similar to what I experienced in the Bullitt, I will do gears instead of selling the car.

Just read the entire thread. Worth 2k to do what you did. I also recently bought a used 16 with the Manual trans and only 331 gears which computes to a first gear in the Bullitt. I swear the car is as fast as my old Bullitt up to 40 miles an hour. Using track aps I can do 0-60 stock in under 5 seconds which could only be done with the Bullitt riding the clutch.

You did good OP. You paved the road for the rest of us.

 

[Brazos609]

...I am close to ordering a 2021 Mach 1 where the gearing is similar to the Bullitt. Originally I was going to order it with the a 10, but in the meantime I bought an 18 and ProCharger it with the a 10. Now I'm looking to do the Mach 1 with the Tremec. If it is similar to what I experienced in the Bullitt, I will do gears instead of selling the car...

I certainly agree, I think the MT82D4 in the Bullitt and other 18-20 GTs is very poorly geared. The only redeeming feature of the MT82D4 is rev matching in the 19+ version. I have the MT82 in my 15 and it has better, more closely spaced ratios than the MT82D4 but I have a 16 TR3160 sitting on the floor in my garage because it has even better, more closely spaced ratios than the MT82 in the 15-17. I'm really looking forward to the rev matching TR3160 in the Mach 1. That will be a great transmission for me because I'm not worried about drag racing. Unless you know something that I don't, the Mach 1 TR3160 will have the same gear ratios as the 16-20 GT350 TR3160 has had and won't have the double overdrive ratios of the 18-20 MT82D4.

 

[Norm Peterson]

Unless you know something that I don't, the Mach 1 TR3160 will have the same gear ratios as the 16-20 GT350 TR3160 has had and won't have the double overdrive ratios of the 18-20 MT82D4.

There's nothing wrong with "double overdrive" as long as you're set up to actively use 3rd, 4th, and 5th in your driving. It's arguably better than having to choose between a 1.00:1 5th gear(revving higher than necessary for relaxed cruising) and a 6th at 0.6-something that's too tall for anything except Interstate running. There are lots of situations that are better served by having a ratio tucked midway between those two.


Norm

 

[shogun32]

the Mach 1 TR3160 will have the same gear ratios as the 16-20 GT350 TR3160 has had and won't have the double overdrive ratios of the 18-20 MT82D4.

that would be nice and since Mach has the fuel guzzler tax, might as well give us better ratios than trying to cheat uncle sam. But unfortunately I wouldn't put it past Ford to screw this up and give us an off-the-shelf with double-overdrive.

There's 4000 RPM-wide powerband on the Coyote3 so close-gearing isn't a necessity and for street use the -D4/3.73 is perfectly fine. Since the Mach has 'track' pretensions maybe it'll mimic the GT350.

 

[GreenS550]

2 overdrives is total nonsense. 6th is totally unacceptable.

I've had muscle cars back in the day with 4 10 and 456 gears with engines that had 5500 redlines not nearly 8k redlines. There is no reason to have the gearing the 18 up had. None.

I am a serious Mach 1 prospective buyer, not a talker that doesn't spend money. I hope Ford gets the gearing right.

It's my belief that there are so many Bullitts for sale used because of transmission gearing, not the Getrag.

 

[WildHorse]

shifting at 7500 rpm with 18+ MT82 & 4.88 gear & 28" tire

1-2 drops to 4800 rpm
2-3 drops to 5100 rpm
3-4 drops to 5300 rpm

shifting at 7500 rpm with the 15-17 MT82 & 3.73 gear & 28" tire

1-2 drops to 5200 rpm
2-3 drops to 5000 rpm
3-4 drops to 5800 rpm

As you can see, even with a 100 rpm disadvantage 0n the 2-3 shift,
the 15-17 is still much better. The 18+ trans can keep it's wide ratio w/ double overdrive haha.

 

[GreenS550]

LO556Bullitt had shown is the way to mod gears. That's the lesson here. If/when I purchased the Mach 1, all it will take, apparently, is a custom tune to keep the speedometer and electronics working accurately.

OP I'm assuming that the tune from Steeda is James's tune as well?

 

[shogun32]

shifting at 7500 rpm with 18+ MT82 & 4.88 gear & 28" tire

1-2 drops to 4800 rpm

shifting at 7500 rpm with the 15-17 MT82 & 3.73 gear & 28" tire

1-2 drops to 5200 rpm

as long as the starting RPM for a gear is at least 4000 RPM it doesn't matter. You're at full torque above 3500. And shifting at 7500 is just wasting time in the thin zone. over 6500 is where it drops off and no point past 7000.

Most people run 27" tires or 26.

 

[WildHorse]

as long as the starting RPM for a gear is at least 4000 RPM it doesn't matter. You're at full torque above 3500. And shifting at 7500 is just wasting time in the thin zone. over 6500 is where it drops off and no point past 7000.

Most people run 27" tires or 26.

K ur missing the point. Tire height is an arbitrary number, so is the shift point. FTR, coyote cams are good to 7300, so shift at 6.5k if you want, I'm going at 7.5k

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