One last question

"YSI-what can brown do for you" (ysi-what-can-brown-do-for-you) 12/02/2013 at 03:35 • Filed to: None

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Are there any ill effects of installing a different FD from stock other than higher fuel consumption? For example, problems with axles, differentials, transmissions, and so on. I am not planning on doing this anytime soon(see anytime past the next 2 years), but it is a good idea for me since it will make the car faster without having to change the engines power output

Manuél Ferrari > YSI-what can brown do for you 12/02/2013 at 03:42

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Hmm. I hand't considered the impact on axles, differentials or transmissions. My guess is that unless you made a severe change the rest of the components would be fine and it would mostly be fuel consumption that was impacted.

If you change the FD to improve acceleration you will shift more frequently when driving around town. So it will wear your clutch a little sooner. But not a huge deal. The biggest impact will be the shorter OD gear that reduces fuel economy on the highway.

I read a pretty interesting article on FD ratio mods for the track. Whether or not the mod will help with track times depends on the layout of the track.

daender > YSI-what can brown do for you 12/02/2013 at 03:48

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Easy fix, the Ford Mustang Cobra IRS system nearly bolts right in place with an aftermarket cradle setup designed just for it. The best part is that you'll find them in spades because nearly every Terminator owner is swapping to straight-axle for drag usage. Also, the tried and true t-56 out of an f-body will remedy any tranny worries. Or just go for a full-on LSRX-7 conversion to eliminate just about every rotary worry possible.

YSI-what can brown do for you > Manuél Ferrari 12/02/2013 at 03:51

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The clutch and gas consumption isn't too important. The biggest benefit to this mod is apparently the revs will stay within peak power output when autocrossing and tracking the car. Hopefully, that is the case 90% of the time. If anything, it will make acceleration that bit more fun.

orcim > YSI-what can brown do for you 12/02/2013 at 03:55

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I'm assuming that this is a manual, correct? (I assume it is considering the forum.) I think I'm with rusto in that if it's not too much of a change, the normal margins for wear will cover you.

The automatic is different of course, since the shifting is done by computer, and the output speed sensor / computer firmware would need tuning to get it to deal with the change. I've had the interesting experience of putting a later model tranny into a earlier less HP model, with different FD's...interesting effects (but useable in normal driving.)

Squid > YSI-what can brown do for you 12/02/2013 at 03:57

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Because I kinda like answering your questions. . .

The final drive is going to have an effect on the total torque multiplication going to the axles and increase driveline stress but I don't have the smarts to know about that. Mostly you run into gearing issues and durability issues once you start adding massive shit tons of power. Stock level power you shouldn't have any issues unless you make the car unusable by choosing ridiculous gears.

YSI-what can brown do for you > orcim 12/02/2013 at 03:59

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Well stock is 4.1 and I am thinking about moving up to a 4.5, so it shouldn't be to much of a change, right?

YSI-what can brown do for you > daender 12/02/2013 at 04:00

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Wait, what is this about Mustangs?

Manuél Ferrari > YSI-what can brown do for you 12/02/2013 at 04:01

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You will definitely improve acceleration! And track performance will improve, on some tracks. On others it will actually decrease due to extra shifting and not having an ideal gear for certain turns. You know how sometimes you hit a corner that you have a perfect gear for and other times it feels like you can't find the right gear for it? When the FD is altered the corners that had perfect gears may no longer have them and those that didn't may now have them.

YSI-what can brown do for you > Squid 12/02/2013 at 04:05

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So lower final drive will lose torque, which would save the axles? I will mostly like be around stock power levels(+30ish hp on top of that). I am not changing the gearing that much. It is going from a 4.1 to a 4.5, which shouldn't be too much.

And I am glad you enjoy my question. I like to get answers :D

orcim > YSI-what can brown do for you 12/02/2013 at 04:06

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9% delta, ... that would seem fine to me. I'd do it if that melt's your butter.

daender > YSI-what can brown do for you 12/02/2013 at 04:06

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I saw FD, immediately thought Rx-7. This is why I shouldn't be posted at 4am, hahahaha. My bad, I misread and my mind went awol.

YSI-what can brown do for you > Manuél Ferrari 12/02/2013 at 04:07

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Yeah that does make sense, you can't really have the optimal set up for every track. Unless you make it a race car, then you just change out the gears because you can.

YSI-what can brown do for you > orcim 12/02/2013 at 04:08

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It does melt my butter, a faster car always melts my butter.

YSI-what can brown do for you > daender 12/02/2013 at 04:09

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Its all good, from my understanding though, changing final drives in Mustangs if fairly common and pretty simple.

Manuél Ferrari > YSI-what can brown do for you 12/02/2013 at 04:10

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Exactly. Or at least just change the FD ratio for each track. Which I read is very common. The FD mod is a great one because with one change the ratio of all the gears changes.

From what I read it's a very useful track mod for experienced drivers. For average to moderate drivers the stock setup works fine.

YSI-what can brown do for you > Manuél Ferrari 12/02/2013 at 04:12

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Sounds about right. I am not planning on doing this anytime soon, it is more of a "is this a good idea or not." I need some nice coilovers and wheels/tires, and tons of track time! Then I will start to conciser this sort of stuff!

orcim > YSI-what can brown do for you 12/02/2013 at 04:15

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Butter Melting is Good. ;)

Manuél Ferrari > YSI-what can brown do for you 12/02/2013 at 04:16

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All fun stuff!

YSI-what can brown do for you > Manuél Ferrari 12/02/2013 at 04:18

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All expensive stuff :(

Manuél Ferrari > YSI-what can brown do for you 12/02/2013 at 04:22

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Don't end up like me! Drowning in debt cause of my cars. And I don't hang out with my friends anymore. I just work and hang out with my oppo pals online

BiTurbo228 - Dr Frankenstein of Spitfires > YSI-what can brown do for you 12/02/2013 at 05:10

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Depending on where the FR-S takes its speed reading from, you might have an inaccurate speedo. If it's mechanical from the back of the gearbox it'll be off, if it's from the diff it might be the same.

thereisnospork > BiTurbo228 - Dr Frankenstein of Spitfires 12/02/2013 at 06:13

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Yup speedo will likely be off unless its using a wheel speed sensor. Should be an easy ratio fix in the computer that the dealership or a well equiped shop should be able to take care of. If not you might need an aftermarket speedometer gear, I know they are popular when swapping FD's on Fox Bodies but I assume by now everyone as moved to electronic pick-ups instead of cables.

Also technically you might lessen the life of the engine if you do a lot of highway driving - due the the higher revs in top gear but the effect should be fairly negligible and no worse than simply driving faster or keeping the car in a lower gear.

Arch Duke Maxyenko, Shit Talk Extraordinaire > YSI-what can brown do for you 12/02/2013 at 07:14

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You'll be able to spin the Prius tires more easily, acceleration will be quicker, top speed will be lower as will your fuel economy. There won't be any effects on your drive train parts.

It may be cheaper to just ditch the Prius tires.

YSI-what can brown do for you > Arch Duke Maxyenko, Shit Talk Extraordinaire 12/02/2013 at 12:05

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Well this is a Toyota part and it costs a total of 600 bucks, so it is too bad on the wallet. I am ditching the Prius tires, and wheels first though.

Arch Duke Maxyenko, Shit Talk Extraordinaire > YSI-what can brown do for you 12/02/2013 at 12:09

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Just stick with the wheels and tires. Does your Effff Arrrreeee Essssseee have an LSD?

YSI-what can brown do for you > Arch Duke Maxyenko, Shit Talk Extraordinaire 12/02/2013 at 12:17

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It does, it has a Torsen LSD.

YSI-what can brown do for you > BiTurbo228 - Dr Frankenstein of Spitfires 12/02/2013 at 12:19

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From the people who have done this mod, their speedometer has read accurately.

Arch Duke Maxyenko, Shit Talk Extraordinaire > YSI-what can brown do for you 12/02/2013 at 12:19

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Don't bother changing it then. You'll be much happier with better tires.

BiTurbo228 - Dr Frankenstein of Spitfires > YSI-what can brown do for you 12/02/2013 at 12:42

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Lucky bastard.

I'm going to have a really tough trying to get the speedo in the spit to work right. It'll have the engine and gearbox from a 2500 PI, Spitfire wheels and a diff ratio that's different to both.

Squid > YSI-what can brown do for you 12/02/2013 at 15:12

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If I remember correctly, you will be increasing the available torque to the rear end by .4 times what it was before. All the little gears multiply the engine torque so in effect if there is 100 ftlbs of torque going to the rear end the 4.1 would multiply the torque out to be 410 ftlbs getting to the ground. So that same car would get 450 ftlbs with the 4.5 gearing. Now it also increases engine RPM to a higher value at a given speed by going to a lower gearing. The point of lower gearing is to increase the torque multiplication factor and allow the motor to work in its power band.

It is kinda backwards but lower gearing means a higher ratio.

A quick search gave me this site which is focused more on the musclecar and drag racing crowd but gear ratios are all the same when it comes down to it.

read about gearing here

YSI-what can brown do for you > Arch Duke Maxyenko, Shit Talk Extraordinaire 12/02/2013 at 17:58

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Fair enough, then. Thanks for the help!

YSI-what can brown do for you > BiTurbo228 - Dr Frankenstein of Spitfires 12/02/2013 at 18:05

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You have quite the job ahead of you. Hopefully all goes well!