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MT-82 D4 gearing question

Velocityblue5oh

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Hey guys excuse me if this is a noob question,
Can someone explain what the problem is for the gearing in the 18-23 S550s compared to the gen 2's? For example, I have a 21 PP1 mustang with 3.73 gears Naturally aspirated platform. Why then, am I at a disadvantage against someone in a 15-17 PP1 with 3.73 gears naturally aspirated?? From what I understand In NA form the 15-17 have an advantage because of their gearing. How is this, if for example the 15-17 is a Gen 2 PP1 with the same 3.73 gearing? However, when going boosted/forced induction the 18-23 have an advantage because of the gearing over the 15-17.
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@Velocityblue5oh are you looking to stay NA or go boosted? Street car, track or drag?

As it stands right now, I can cross the stripe in the 1/4 in 3rd with my D4, at about 7200+ rpm. I’ve contemplated adding a 4.56 out back, but it would be a lot of work and money. I’d hate to do it if one of these days I decide that I want boost. Then I’d be back at it changing the rear gear once again.
 
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Velocityblue5oh

Velocityblue5oh

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@Velocityblue5oh are you looking to stay NA or go boosted? Street car, track or drag?

As it stands right now, I can cross the stripe in the 1/4 in 3rd with my D4, at about 7200+ rpm. I’ve contemplated adding a 4.56 out back, but it would be a lot of work and money. I’d hate to do it if I one of these days I decide that I want boost. Then I’d be back at it changing the rear gear once again.
Mostly street car. Currently Im stuck deciding If I wanna save and get in a mach 1 HP with a tremec or save for FI if I am unable to get a deal within my budget. Looks like my best route currently would be to keep the stock gearing until I decide on which decision to make.
 

Silver Bullitt

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The MT82 in pre-2018’s has a really short first gear and 1:1 is 5th gear. The MT82-D4 has two overdrive gears and 1:1 is 4th gear. IMO, the D4 is set up better for street driving while the MT82 is set up better for tracking. Although, as mentioned earlier, in basically stock form, it’s possible to trap the 1/4 mile in 3rd gear in the D4 saving a shift.
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Dave2013M3

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A set of 4.09 gears goes a long way in fixing the issue with the MT82D-4. Ask me how I know...:D
 

Duece McCracken

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@Velocityblue5oh are you looking to stay NA or go boosted? Street car, track or drag?

As it stands right now, I can cross the stripe in the 1/4 in 3rd with my D4, at about 7200+ rpm. I’ve contemplated adding a 4.56 out back, but it would be a lot of work and money. I’d hate to do it if one of these days I decide that I want boost. Then I’d be back at it changing the rear gear once again.
You can buy a loaded 3.73 Torsen for the swap back. Or even a used diff. Then it's just bolt out, bolt in to go back to 3.73. Which is my plan, lol
 

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The MT82 in pre-2018’s has a really short first gear and 1:1 is 5th gear. The MT82-D4 has two overdrive gears and 1:1 is 4th gear. IMO, the D4 is set up better for street driving while the MT82 is set up better for tracking. Although, as mentioned earlier, in basically stock form, it’s possible to trap the 1/4 mile in 3rd gear in the D4 saving a shift.
E411ADE7-1F74-46D9-B2D5-9BCEC694744A.png
I had no idea it was this big of a difference. I have 3.31s and the old MT82 and I think first is fun.

The Tremec ratios seem good.

D4 seems like it legit needs the 3.73.
 

ShadesOfBloo

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I had no idea it was this big of a difference. I have 3.31s and the old MT82 and I think first is fun.

The Tremec ratios seem good.

D4 seems like it legit needs the 3.73.
Part of the difference in perception is that the newer cars that have the D4 also have a redline 400rpm higher.

Where a 2017 GT-PP could go 64mph in 2nd gear, a 2018 GT-PP can go 78 in 2nd gear.
...So, with the combination of taller 2nd gear and higher redline, you're waiting longer for the shift to 3rd.

Also, out of the 3 transmission choices the D4 has the biggest gap between 3rd and 4th gears. One more reason to avoid shifting to 4th at a track or drag strip: You would lose a lot of rpm.

A car with the D4 can also trigger the 155mph governor in the top 3 gears. I don't know if that's really a downside, but it's silly 🙃

While I understand that a rear-end swap is way less expensive than a Tremec swap...
A 4.09 rear end would have your engine turning faster at 75mph, where a Tremec swap would barely make a difference in 6th gear, while making the car faster in all the other gears.
(To me, the fact that my GT-PP1 turns only 2100rpm at 75mph is a major selling point, and I don't care to change it.)

Another thing to consider is that different Mustang trims come with different size tires, and that can change the effective gear ratio. The next time you need tires, you could try a size that gears your car shorter.
GT-PP2 came with the 3.73 rear end, but the tire size made it like putting a 3.90 in the car.
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