Paris MkVI

Help out a Mustang fan who wants to more fully understand the ramifications of a rear gear swap. Referencing the 2005.

Here's how I understand it:

If you put 4.10 gears in the rear, you're faster off the line. You'll lose some top speed, since you will rev up to the redline quicker.

How much top speed do you lose? Is there a measurable, significant improvement off the line with the 4.10's?

Do you need to flash the engine control module along with the gear change? If not, what additional advantages would you get from doing the flash along with the gear change?

If a Ford dealer installs the 4.10 gears, does the factory warranty remain intact?

Thanks for your responses and help!

Kluski

Does that mean you lose the "top speed" in each gear, since you reach the red line quicker?

swingle007

Just a lower top speed after the gear change...Certainly not a slower speed in each gear as mine shifts from 1st to second at about 50mph and will shift from 2nd to 3rd at 80mph....of course this is with the pedal to the floor.....hope this helps....

John

joeuser42

Thanks for asking this question Jon. Wifey has given me the go ahead to put some cash into modding my stang. I also am looking to swap in 4.10s. I never take it over 100mph anyway so I don't really care about top speed. I think I read that a flash is necessary to correct the speedo, so I was going to combine that with a 92 octane flash.

Another question to add to your list is: "Will the 4.10s require wider rear tires to hook up at least as good as it does now?".

swingle007

I don't have any MAJOR traction issues with the stock tires once they are good and warmed up...They'll bark a little when ya floor it from a standstill and that's about it....Obviously some larger ones might aid you in the holeshot....My factory set is just fine until I find an aftermarket set I REALLY like....not super pleased with any I've seen so far for the '05...

swingle007

In answer to some other questions, yes you will need to reflash it using SCT or some other company to gte your speedo reading accurately again...It'll be off between 10 and 15 mph on the fast side after the gear change....The difference off the line is incredible with the 4.10's...I'd be willing to bet it saves a half a second getting to 60mph...It's a BIG difference that you will definitely notice...As far as the top speed goes, I can still easily get mine up over 120 without a problem although it turns some high rpm's to get up that fast now with the gear switch...I would recommend the gear switch to anybody looking for a great acceleration improvement for a small investment (500 bucks or so with pro install).....I would also have to assume that if Ford did the switch that it would have to fall under warranty with them...

ZERO

john, does ford actually do the gear change? so...say you can go to your dealers parts shop, purchase some motorcraft 4.10's, and have them do the install?



if they can do that, i'd be very interested in that.

tmcolegr

I just spoke to my dealer's Service Manager and his response was "your warranty will stay intact if the dealer does the install". However, it's very pricey from the dealer. I was quoted $720.00 for labor only. That's with me supplying the Ford Racing gear set and lube. So basically your looking at about $1,000.00 for P&L. I additionally asked him about flashing the computer to compensate for the gear change (3.73 in my case as I have an automatic). His response was "no problem, shouldn't take more than 1 hour for that".

So I guess it all depends on how warm & fuzzy you want to feel. Spend less with no factory warranty coverage or spend more for coverage. It's up to you. Let your wallet be your guide.

One question for those of you that have already done a gear change. Besides the gear set which includes ring & pinion, pinion shims, crush sleeve and lock nut, are any other parts required? For example ring gear mounting bolts, the inner pinion bearing and associated seals. I have already bought the golden ($60) synthetic lube and friction additive from Ford.

426H

:scratch:

As switch to 4.10 will lower your speed at ANY rpm at ANY gear but of course more at higer gears.

ZERO

hey john,

do you remember if there is any specific dyno tuning to be done for the gear change? or is it simply a matter of them telling the computer you now have 4.10 instead of 3.55 in relation to RMP and MPH?

GarageLogic

It is simply making a change on the CPU's speedometer calibration table, it does not require a dyno tune.

I am with swingle on this one, putting gears in my cars made all the difference. I have 4.10's in my '03 Mach 1, 4.10's in the '05, and 3.80's in the '65 fastback.

ZERO

is the installation and a re-tune all that is required? a friend of mine mentioned that you had to do a lot more than just a re-tune. something about re-syncing the cam, but he didn't have time to go into why you have to do it.

any thoughts on this? is he just thinking of older cars? he has a 70's something impalla that he does a lot of work on...i thought maybe he just wasn't up to speed on all the new technology.

GarageLogic

Don't listen to your friend. Camshaft timing is the relation of the camshaft to the crankshaft. Changing the rearend gears does nothing to affect this relationship. This is true for new AND old cars.

Paris MkVI

I had a feeling the flash was required for the Speedo to be correct.

I'm of the persuasion that faster off the line is more fun - the top speed is likely something I would never use. I don't hit the track or the strip - just enjoy a nice stoplight and an empty road.

GarageLogic

Yes, a reflash is needed to calibrate the speedo with a gear change, but it does not require a DYNO tune.

tmcolegr

I agree with Jon. Top end is not an issue for me - 80 MPH tops on the interstate. However, 0 to 80 is definitely a priority. You have to do a lot of engine mods to get the same "seat of the pants" feel associated with a gear change. Issues related to engine mods are not for me. Just a gear swap and Magnaflow AxleBack kit.

clintoris

here's my $.02... I think I would be more concerned about a proper installation than I would about the factory warranty. So many people out there will swap gears for you, and no matter what price they charge, some people just can't do it right. If I were you, I'd find a rear end guy that you know can do the job right, and will warranty his own work. If you swap gears, it's not going to afffect anything with your warranty unless it can be determined to be the cause of a failure. If you have someone swap gears, whether it's the dealer or a Joe Bob Rear End job, and they do a lowsy install, you're going to have a failure, and it's going to cost you. I would be willing to bet that the guy at your dealer that told you your factory warranty will not be void on the rear end if you swap gears was incorect by telling you that. That dealer will probably warranty their work, but I'll bet they'd have a hard time convincing Ford to reimburse them for a failure due to a modification that they caused. See what I'm saying? If the gears are installed properly, you won't have any problems, and it will far outlast your waranty anyways. I would find the best differential specialist you can find, and have them do it. Ask your friends, co-workers, neighbors.... you're probably not the only gearhead in your area, and someone can give you a good reference. Just because it's a Ford dealer tech doesn't mean they are perfectly capable of the proper install. I had my gears changed out by a dealer tech when I did it, but he also happened to be the best around. Did a great job. I never even asked about the warranty, and I didn't want to poke too far into it because the whole procedure happened to be a warranty problem to begine with where they had to replace the carrier and bearings, and because of subsequent wear on the pinion shaft, the gears had to go too.... I just worked a deal with the parts guy, who was a good friend, and we snuck in some 3.73s...

The moral of the story is.... if your installer knows his business, whether he's employed by the dealer, or it's a friend of a friend that works out of his garage, the warranty will not be an issue. I'd be more concerned about the quality of the work.

ok, that was more like a dollar instead of 2 cents.

Kluski

How do these gears effect you in the 70 - 80 mph range. I do drive a lot of highway and would not want to effect that negatively.

Paris MkVI

Thanks Clint - that was a worthwhile "dollar".

ZERO

How do these gears effect you in the 70 - 80 mph range. I do drive a lot of highway and would not want to effect that negatively. [/b][/quote]
so do i. i think 75 is about as fast as i typically go on the freeway...and i've seen someone do the calculation on the RPM difference at 60mph. it was a 400rpm increase if i remember right at 60mph in 5th gear. anyone notice a change in MPG?