Going from 3:31 to 3:73?

[spacemarine83]

So I have a the 3:31 gears in my Mustang and was wondering how much more responsive the 3:73s are in comparison?

The last mustang I did a gear swap in was my 08 and went from the stock 3:31? to a 4:10. It made a huge difference.

Would I be seeing the same kind of pickup In acceleration because in my '17 the 3:31s just seem really lazy.

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[whatsup62]

Yes you will feel quite a difference. If you plan on EVER going boosted stay with the 3.31's

 

[09jsw]

I just swapped from 3.73 to 3.31. The dif is dramatic. I am boosted now and that’s why I made the change. It’s still hard for me to get used to the looooong gears even for normal driving. My car always hit pretty hard with the 3.73.

 

[BmacIL]

I'm still looking for a trade for 3.73s.

 

[hiccup]

Do the 3:73s..then you can skip shift and spend less time shifting...may even improve overall mpg.

 

[gcadorette13]

I am also looking to go from a 3.31 to a 3.73.

 

[spacemarine83]

Yes you will feel quite a difference. If you plan on EVER going boosted stay with the 3.31's

I have considered going with a boosted setup, but given where I live and what roads I drive, I do not really think I need more power...just the ability to access it quicker with gearing I think.

Any thoughts on overall pickup of 3:73 vs 3:31? To me, it feel as if the car is trying to catch up to itself with 3:31s hence why I want to change.

 

[jabrax]

I have 3.73 and boosted. If i find a local 3.31 that wants to swap, I probably will. 3.73 boosted is tough. 1st gear is useless, and second not much better. Yes they hit harder than 3.31. I got to drive a friends 3.31 naturally aspirated. 6th sucks if you need to give it gas. 6th with 3.73 has reasonable acceleration.

 

[Grintch]

I have 3.73 and boosted. If i find a local 3.31 that wants to swap, I probably will. 3.73 boosted is tough. 1st gear is useless, and second not much better. Yes they hit harder than 3.31. I got to drive a friends 3.31 naturally aspirated. 6th sucks if you need to give it gas. 6th with 3.73 has reasonable acceleration.

That is why you have multiple gears.

So 3.73's make 1st (& second per above) useless. 3.31 makes 6th useless.

Use 6th as a fuel economy gear (which is what it is), and shift down when you want decent acceleration and the 3.31 is great.

Now with the taller gearing of the 2018+, the 3.73 makes more sense. But for a 2015-2017 the 3.31 is the better choice.

 

[TheLion]

That is why you have multiple gears.

So 3.73's make 1st (& second per above) useless. 3.31 makes 6th useless.

Use 6th as a fuel economy gear (which is what it is), and shift down when you want decent acceleration and the 3.31 is great.

Now with the taller gearing of the 2018+, the 3.73 makes more sense. But for a 2015-2017 the 3.31 is the better choice.

3.55 is a good middle ground for first gen S550 6M's if you have power adders. I have a 3.73 Torsen in a PP GT and yes, 1st is short, I top out at 42 mph in 1st gear, 65 in 2nd and 93 in 3rd, 120 in 4th and that's WITH a Power Pack 2 that allows me to rev out 350 RPM further than stock.

Bone stock with a rev limit of only 6800 RPM it was just too short and just not optimal to shift so quickly. I felt like I was always running out of gearing. It was a drag gearing pure and simple and to me did not seem like a track gearing which the Performance Package was marketed as. The Power Pack 2 helped a decent amount and made 3.73's decent in terms of giving it longer legs.

It may not sound like much, but it definitely makes a difference. 3.73's would be really good for Power Pack 3 with it's 7450 RPM rev limit, it's a perfect combination with Power Pack 3's linear power band and still some what flat mid-range, the lower 3.73 gearing is an excellent complement. I will say that I do like 3.73's with Power Pack 2 as well, not sure I'd want to gear up, especially when you have a full passenger load the shorter gearing keeps the car more peppy.

Honestly if you run shorter 3.73's, I'd imagine you could stay in 3rd more often than with 3.31's, so it may work out on some tracks or roads by allowing you use the next taller gear and stay in it. I've not heard anyone complain about 3.73's with the 2nd gen MT-82 on an actual circuit track.

The 2018's have different ratios, I believe they are similar to the Option B ratios of the standard Tremec 6060 used in the GT350 (Camaro SS uses Tremec 6060 Option C ratios): http://www.tremec.com/anexos/TREMEC_TR-6060_1017.pdf

You could always do a transmission conversion as well for better ratios. But honestly the biggest issue with the 2nd Gen MT-82 is the following two items:

1. The OE fluid does not perform well, especially over temperature. BG SyncroshiftII makes a substantial difference in shift quality and effort, especially when cold. I actually had issues with 2nd gear failing to engage completely even when it felt like it was in and it would grind, Syncorshift II dramatically helped.

2. The shifter turret remote mount arm where it connects to the MT-82 tunnel uses rubber bushings. Those bushings while reducing NVH quite a bit also allow a lot of flex (1st gen MT-82's were worse) and consequently the gates get misaligned causing you to miss gears (narrows the already narrow gates), make shifts difficult and imprecise etc.

Ford Performance short throw shifter kit has aluminum bushings that replace those rubber bushings and it dramatically increases shift quality. The magic in their shifter kit isn't the shifter itself, you could use any shifter as long as you have those bushings in. It's just as good as any top loader, but yes you get more vibration from it, it's kinda old school feeling, but it works and works very well and I love it.

I never installed the bushings when I bought their short throw kit for my ecoboost because I didn't want to do the work of disconnecting the drive shaft and lowering the trans to install them etc. But I didn't throw them out and kept them in my spare parts. This time, with my GT, I installed them along with a steeda Tri-axes short throw, excellent setup and I can shift efficiently and with confidence where with the stock unit it was hit or miss, imprecise and mushy and worst of all slow because of it's lack of feed back and how it caused difficulty shifting. It completely changed how the MT-82 operates.

I'd wager if you put in the mushy rubber bushings and rubber cored two piece shift stick on any trans it would significantly reduce it's performance, regardless of how well the synchro's mesh or the ratios are. It's no good for any type of performance applications and my GT is a performance street car / occasional track car.

 

[spacemarine83]

Thank you for the informative post! The first mod I did the car was the shifter then the lockout. It made A VAST improvement in quality of the driving experience. Next will be gears. As a fun daily driver, I would like more pick up and go without adding a power adder due to traction issues and living in a place where it rains half the year or so.

 

[TheLion]

Thank you for the informative post! The first mod I did the car was the shifter then the lockout. It made A VAST improvement in quality of the driving experience. Next will be gears. As a fun daily driver, I would like more pick up and go without adding a power adder due to traction issues and living in a place where it rains half the year or so.

I would highly reccomend the Ford Performance Power Pack 2. Yes it's a power adder. Yes you get a big boost of mid-range torque with a little more top end. However it's awesome as an NA setup with 3.73's, but it may give you enough added pickup that 3.31's are much more fun and you won't need to change gear ratios down to 3.73. My car is a Performance Package GT, so it came from the factory with 3.73's just for reference.

I drove it with the stock engine calibration until 17k miles. Then I just had the Power Pack 2 installed at the beginning of June and I have never looked back. Even with 3.73's the stock GT sometimes felt a little too flat in the mid-range. It wasn't slow or "sluggish", but a bit flat and it felt to me like it needed a little more to be just right for a modern NA V8, at least what I envisioned. Power Pack 2 delivered that hands down and even if I had 3.31's I think Power Pack 2 would have been plenty because you can stay in the lower gears longer.

It's a lot less work to have a Power Pack 2 installed than to swap a ring and pinion gear in an IRS diff. To do a gear swap, your going to pay pretty handsomely for a shop to do it. If you do it yourself, you need a case spreader, ring and pinion set, depth gauge, differential seals, motorcraft TA-30 gasket maker, a long piece of L channel and some M8 bolts to make a pinion flange holder so you can loosten the pinion flange nut (it's staked and one time use), a jack and a wooden scaffolding to hold the whole IRS so you can lower it out of the car, a torque dial in inch-lbs to measure bearing pre-load, 3/8 and 1/2 drive torque wrench, 13, 15, 18, 21, 24 and I believe 26 or 28mm socket for the pinion flange nut, 3 lb hammer and a 1-3 foot long 1" square piece of channel, EPL 16 socket....about 16-20 hours worth of elbow grease. And, if you don't get the pre-load right on the crush washer for the pinion, you need to rip that out and re-do it and buy another crush washer as it's one time use also.

Power Pack 2 takes about 2-3 hours to install at your typical dealership or about 1.5 hours for you to install it yourself if you don't care about warranty (I highly recommend keeping the warranty for piece of mind just in case, even though FP has the best reliability track record bar none, you have a lot more to work with should something go wrong).

A Power Pack 2 GT with 3.31's will out run a stock GT with 3.73's any day. Not only that, but you get 350 RPM higher rev limit. So your top speed in 2nd gear is now 76 MPH and 102 MPH in 3rd! Your going to accelerate quicker in 2nd with a 3.31 rear end and Power Pack 2 than you would in 3rd gear with stock engine and 3.73's because 3.73's only get you to 62 mph in 2nd with the stock rev limit of 6800 RPM while Power Pack 2 and 3.31's get you 76 MPH in 2nd. It doesn't sound like your going to likely ever use 4th gear or even 3rd most of the time. So a super tall 2nd will deliver the most fun and in reality the best acceleration to 75 mph as opposed to a 2-3 shift you'd need with 3.73's and the stock calibration.

Plus the throttle response is FAR better with the Power Pack 2 than stock, drive ability issues like the Rev hang when cold (mine did it a lot stock when cold) are diminished or even eliminated in some cars. It's really that good. If you have a friend with a Power Pack 2 and 3.31's or an auto with 3.15's, i'd highly recommend taking it for a test drive.

There's no doubt that Ford Performance out tuned Ford ten to one with the send generation 5.0. I don't think I could ever go back to stock. It's also CARB legal if your in cali, so it is still a road legal modification that meets emissions requirements. That was another important factor for me as I have E-check here in Ohio, while not as strict as CARB, you still won't pass most of the time with after market modifications unless they are designed to be emissions legal.

Based on what you describe, that actually sounds like the best bang for your buck as opposed to a gear swap. Now if you wanted track or drag the car NA, I could see dropping down to 3.55's or 3.73's, but for your application as a fun road car / grand touring car on back roads, I think 3.31's will serve you well when combined with a Power Pack 2.

Plus you then have the ability to data log (yes, pro cal can data log) should you ever have issues, you can change your tire size (to get correct speed and odometer readings), you can change axle ratios yourself (if you do decided to re-gear at some point).

I love 3.73's with the Power Pack 2, it's an awesome combination, but 3.31's have their own merits as well, especially with Power Pack 2 which gives you a power band nearly identical to the latest Alpha based Camaro SS with it's 5th Gen LT1 6.2L straight from the Corvette. It's pretty nice having the same power as the Corvette (albeit in a heavier chassis)!

 

[dharts9]

Yes you will feel quite a difference. If you plan on EVER going boosted stay with the 3.31's

Is this the case for the new 10r80 or just the 6 speed? I got stuck with 3.15 gears b/c I went non PP on my 18 but I do plan to boost.

 

[whatsup62]

if going boosted the 3.15 will work great.

 

[erikkire18]

how difficult was it to switch gears from 3.73 to 3.31, i am also boosted and need to swap my gears but am not sure how hard it will be or how long it will take. thanks

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