IS there any advantage to 3.73 gear upgrade

My experienced advice/comment,
Keep in mind that in the many gear swap threads there are also many different year/model/engine applications that likely differ from your exact application and your results will vary.
I personally went to 3.73 from 2.73 in my 2013 V6 auto expected MORE SOTP feel than I achieved.
With this gear swap I didn't expect the gear whine and DS (or split bearing?) hum in top gear cruising speed that I now have.

I have since been told a couple interesting things by a Mustang mechanic and previous employee of a local service department. One of the highest number of valid returns and redo's were from gear swap customers.
Another item he shared, which I'm not sure how true it is, was that even with a perfectly installed set it is a "roll of the dice" for 3.73 gears in particular on the amount of whine you'll experience.
Lastly he and others I've spoke with on the subject tell me that Ford now outsources their gear manufacturing to Motive. Funny the shop I used required I purchase FRPP and now I learn that they're all made by Motive?..
Anyways theres my input FWIW.

RED09GT said:

With a 28" tire, 4.10's and a 1:1 gear, you can trap 142 at 7000 rpms or 146 at 7200 rpm in the 1/4 mile.

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that's a lot of RMP for a stock 3V valve train and rods

Your mechanic is key to how good a job you get. I had a guy that was highly recommended to do a gear swap. He had done lots of them on Mustangs. Being that he worked at a Lincoln dealership, I also got the Ford racing 2-year warranty on the job. Kids working at a dealership may have done one or two swaps. I wouldn't want them touching my car.

stkjock said:

Oh jeezzzzz....

4.10s if it’s a manual

topic has been done over and over and over.

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UH NOT By me it hasn't !

stkjock said:

that's a lot of RMP for a stock 3V valve train and rods

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Who's trapping 140+mph with a stock valvetrain and rods in the 1/4 mile?

Dino Dino Bambino said:

Going from a 3.31 to a 3.73 increases the rpm (and torque multiplication) in any gear by 12.6% at any given speed. Going to a 4.10 increases the rpm by 24.0% and that's a difference you'll really feel in the SOTP.
The decision on which ratio is suitable will depend on what performance mods you have now and whether you're planning to add more in the future.
BTW, love the wheels on your car. Which ones are they?

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Dino thanks so much for your kind reply, as for my mods they are mostly cosmetic with the exception of the 93 octane tune the cervinis ram air hood and my tire size. Also its worth noting that my Stang is an auto withthe TCI Streetfighter Ratcheting shifter. As for my wheels they re TSW Cadwells 18x 8.5 in the rear and 18x9 in the front.

13v6 said:

Your mechanic is key to how good a job you get. I had a guy that was highly recommended to do a gear swap. He had done lots of them on Mustangs. Being that he worked at a Lincoln dealership, I also got the Ford racing 2-year warranty on the job. Kids working at a dealership may have done one or two swaps. I wouldn't want them touching my car.

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This.
I do not buy into "this ratio gears whine, and it is what it is". IMO this is just BS to keep from having to do the job over again.
That said, I do have some gear whine w/my 3.90s and the install was one of the best and easiest with good contact pattern and backlash.

Just put 4.10’s in my 08 manual that had 3.55’s the difference is night and day seems like a whole new car. No need for down shifting to pass car is always in the power band now it is a little more shifting if you drive a lot in the city but I love it. Other mods to the car are jlt series 3 cai, Ford racing manifold, gt500 60mm tb, sr performance underdrive pulleys, sct-4, 285/30-19 Mickey Thompson et streets and a zex nitrous systems jetted for 100 shot. I haven’t sprayed the car since the gear install but it should be a blast.

I went with 3:73's after a lot of research. Better acceleration and still getting 25 mpg on the highway with FRPP cams and intake. It's a good overall ratio for a N/A street driven car IMHO.

Monkeyporn said:

Dino thanks so much for your kind reply, as for my mods they are mostly cosmetic with the exception of the 93 octane tune the cervinis ram air hood and my tire size. Also its worth noting that my Stang is an auto with the TCI Streetfighter Ratcheting shifter. As for my wheels they re TSW Cadwells 18x 8.5 in the rear and 18x9 in the front.

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OK. That makes the choice easy; 4.10 and upgrade to a TCI 3000rpm stall torque converter. That combination seems to be the sweet spot for stock (or near stock) automatics. Then you'll have to deal with the inevitable traction and wheel hop problem i.e. upgrade rear LCAs.

Dino Dino Bambino said:

OK. That makes the choice easy; 4.10 and upgrade to a TCI 3000rpm stall torque converter. That combination seems to be the sweet spot for stock (or near stock) automatics. Then you'll have to deal with the inevitable traction and wheel hop problem i.e. upgrade rear LCAs.

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Dino from what I've read changing gears requires a new tune to ajust the speedometer...correct ? as for the LCAs my whole suspension as been upgraded and replaced it was all shot when i got the car. I've got he GT500 Front LCAs along with the Ford Performance Rear LCAs Koni Yellow Shocks & Struts.GT500 Strut mounts Ford performance swaybars fron and rear and the ford preformance lowering springs. All the sway bar limks and tierod inter & outer have been replaced along withthe front swaybar links as well. I also have replaced the driveshiaft adding the DDS aluminum one piece.

New gears are a simple adjustment on the handheld if those parameters are unlocked.

Monkeyporn said:

Dino from what I've read changing gears requires a new tune to ajust the speedometer...correct ? as for the LCAs my whole suspension as been upgraded and replaced it was all shot when i got the car. I've got he GT500 Front LCAs along with the Ford Performance Rear LCAs Koni Yellow Shocks & Struts.GT500 Strut mounts Ford performance swaybars fron and rear and the ford preformance lowering springs. All the sway bar limks and tierod inter & outer have been replaced along withthe front swaybar links as well. I also have replaced the driveshiaft adding the DDS aluminum one piece. View attachment 77385

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Sounds like you're already sorted in that department.

stkjock said:

New gears are a simple adjustment on the handheld if those parameters are unlocked.

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What he said. An unlocked SCT handheld tuner allows you to adjust for any change in axle gear ratio, and also allows adjustment of revolutions per mile if you change the tire size.

Yea that’s all I did when I swapped my gears I have an sct-x4 I went in and changed the gear ratio from stock to 4.10 takes 5 minutes. Well it takes 30 seconds to make the change just about 5 min for it to load the change. I drove my car home from the shop before I swapped the tune and the speedometer was off about 20mph when I was doing about 50mph it was showing 70-80mph.

I bought a used 2008 Bullitt 3.73 Posi traction rear end off ebay. Replaced the original 3.31 in my 08 GT.
Car is automatic. Got rear end in and had a bent axle from previous wreck that totaled the car.
Once finished, it does good. Had to have speedometer adjusted for the new ratio. Then installed aluminum drive shaft. It runs a lot better now and still gets good gas mileage.

stkjock said:

Oh jeezzzzz....

4.10s if it’s a manual

topic has been done over and over and over.

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410's if manual get the Ford Racing-good fit and unless you have done this before have someone do it for you if you want to avoid whine as it requires special tools to set lash and clearance and experience.

I got lucky. I have a driveline speciallity shop just a couple of miles from my house. They did my 3.73 Ford Racing gears. They are absolutely quiet. Gears shouldn’t make noise.

I changed form 3.55 to 3.73 (had to rebuild diff anyway) manual gearbox and I noticed some very useful advantage nobody mentioned so far I guess. It's much easier to drive slow.
I'm in Germany and the Green party harassed almost any city to change the speed limit from 31 to 18 MPH. And, one has to stop at any crossing, like a virtual Stop sign. So there is a constant stop-and-go all the time.
Much easier with 3.73.

I'm in Cyprus and the speed limit in residential areas is 50km/h (31mph). I still have stock 3.55 axle gears and at that speed in 4th, my tach is at only 1400rpm. Though the engine still pulls smoothly at that rpm, I tend to use 3rd anyway 'cause I have to slow down for annoying speed humps. Driving around town, I can't stay in the same gear long enough for the axle gear ratio to matter.
The speed limit is reduced to 30km/h (19mph) outside schools and at that speed, I'd have to use 2nd gear anyway.
If I was to contemplate an axle gear swap at all, it would have to be a 4.10. A 3.73 would be too small a step up to be of any use.

RED09GT said:

Shifting gears has never bothered me so the short 1st gear would never be an issue to me.

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In most situations, I don't mind the gear shifting itself. But with 4.10s and 27" tires, upshifting out of 1st at 4000 rpm would be happening at 22 mph and be annoying rather than fun. No bueno for turning into a gap in 45-50 mph traffic from a side street or business parking lot (a fairly common situation where I live). Let's just say I'm not a street racer / drag racer / WOT in 1st gear / powershifting kind of driver and leave it at that.

3.73s would be a gear you'd choose based on fitting the speeds in gears to your performance driving, where 3.55s would be just a bit too tall and 4.10s too short. So when your performance driving preference runs toward road courses and HPDE, not having to grab that way-too-tall 0.68 5th gear matters and 1st gear acceleration is completely irrelevant.

The 3.55's were terrible in the 1/8th mile as I had to shift to 3rd 100ft from the stripe.

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That's a lot like what I'm getting at with wanting to avoid having to upshift into 5th somewhere on the longer straights.


Norm