I already emailed Troyer but I thought someone on here might know as well. I have a 2000 F150 5.4 4x4. I am planning on getting larger tires (33's) for this truck very soon. My problem is that I have 3.31 gears (not very good) and my gas mileage, shift points, speedo and everything else is going to be out of whack. I dont care about offroad capability, so the fact the my gear ratio will get even worse with larger tires is no big deal. I would just like a program that will let me use 87 octane and restore my trucks preformance a little without changing my gears. I just want to truck to not have to work hard to turn the tires and get 9mpg. I am not looking for a miracle, but can the 9100 solve my problem. I cant order tires unitl I know i can fix everything without new gears. Thanks.

 

I think that 3.73 gears would be your miracle...A tuner would help, I'm sure, but you need a different gear ratio..

 

that is what i was afraid of. I already bought 16x10 wheels thinking i had decent gears and could get larger tires. Now i am stuck with my wheels and cant get bigger tires without gears.

 

these are VERY heavy trucks and those 3.31 gears just can't get it moving. I have the FX4 with 17 rims and 3.73 gears and I can light up my tires. My tires measure out to about 32s so there isn't a huge difference, but I think you'll probably want new gears...

they may not be as expensive as you think...

www.drivetraindirect.com

I think...

 

Well, i emailed them to see how much it would cost me, but i still have the feeling it will be out of my price range. Not to mention that i will have to get tuned after anyway to fix my speedo and ect.

 

Hi 00,

A fair number of people do just that - they'll go with the taller tires and then have us do a tune to bring power up as well as fix the speedo, shift points, etc. issues, to hold them over until they can afford to get the gear ratio change.

Now most people who do that have the 3.55 gears, but we can do that for the 3.31's as well, of course.

I do agree in that with 33" tall tires, the truck should have more gear than 3.31's - but that is something that only the *owner* of each individual truck can decide. I have customers running configurations that I felt sure I would hate to drive on stock gearing, and they're perfectly happy with the results - go figure!

Look at it this way - if you already have the wheels & tires, just have us go ahead and do the custom tuning to get you as much power as possible, and then as time goes by, work on saving towards the gear ratio change if you feel you need it for the manner in which you operate your vehicle.

Best of luck, whatever you decide!

 

Thanks for the help. That is what i am going to do. By the way my truck is stock other than the tires I am about to put on it. I really have to get an exhaust system on this truck. I am sick of running in stealth mode. It is just way to quiet for me, plus from what others say i will get better power and mpg with it. I plan on getting it done by Christmas time. Will I have to get custom tuned again or does it not make a big difference?

 

We do not need to change anything after the installation of a good quality cat-back exhaust system on these vehicles, so you'll be fine there!

One word of caution - be *very* careful of what you do exhaust-wise, as most exhaust mods actually cause a LOSS of torque below about 2800-3000 rpm, with a resulting loss in mpg, too. Give us a call for derails on exhaust systems that will avoid those problems.

God luck!

 

I have a very good exhaust guy in my town that works on race cars. He pays real close attention to cfm and sugested a single in dual out custom spintech setup. I trust him but I am sure your computers are smarter than he is. Do you think it is just better to leave it stock in the situation that i am in with my gear ratio.

 

Hi 00,

Our computers are the same as everyone else's, actually. However, we are pretty good at what we do, which is specialize in F-150 performance. I don't want to get into lengthy details as this is off-topic for this section of the boards, but a quick comment or four...........

What we have to look at in these trucks are more than just the peak HP gains at full-throttle or CFM’s, but also knowing the exhaust requirements of these heavy trucks using small overhead cam gas motors, knowing what the factory exhaust does and doesn't do, and then also knowing just what the actual results are from the various aftermarket cat-back systems. The "hidden kicker" in all this that most people aren't aware of, is that the factory exhaust system does *one* thing very well in the 1997 & up F-150 - provide relatively high exhaust gas velocity at lower rpms & throttle openings. So the factory exhaust, though far too restrictive to be efficient under a real load, delivers decent torque in those areas where the vehicle is most often operated - below 3000 rpm and at less than about half-throttle. That fact, combined with the fact that almost nobody in the aftermarket exhaust business actually does flow engineering specifically for these trucks to get the exhaust gas velocity back up so low rpm torque is not reduced, and you have a situation where almost anything you do to open up exhaust flow will get you some HP gains at higher rpms, but you also lose torque at lower rpms, and that's with most cat-back systems - name brand or "custom."

Magnaflow gets us the best actual exhaust results on these trucks - not only in peak power gains, but also everywhere else where the truck really needs it, so that lower rpm torque, driveability & fuel mileage don't drop compared to the stock exhaust. Magnaflow is the only exhaust manufacturer whose systems we've seen actually increase available torque everywhere in these trucks, and that happens both with their 3” single as well as their SIDO cat-back system for the F-150. If you want to add a "custom" touch to the exhaust, you can always have your local guy weld in a new Y-pipe intersection (that's just ahead of the cat-back system, and just after the catalytic converters - the place where it reduces down from dual into single), as the factory intersection isn't the best.

Overall, I'd say installing 33" tires on a truck with only 3.31 gears means the *last* thing you can afford is for that truck to lose low-rpm torque. So if I had to choose between a “custom” Spintech setup or the stock exhaust, I’d pick the stock exhaust – but the best choice is going with the Magnaflow setup. Now if you have your heart set on this custom Spintech setup, some of the lower rpm torque loss that will result can be offset by having us do a good custom tune for the truck - our custom tuning absolutely will result in more torque and horsepower everywhere, at any throttle position, and at any rpm, and that will make a nice running setup at full-throttle.

By the way, I wouldn't expect a “significant” mpg gain just from a cat-back exhaust system on these vehicles, due to the aforementioned low rpm torque characteristics of the stock factory exhaust - many systems actually cause a small *loss* in mpg due to the lower rpm torque loss. The best results we've seen (both in terms of performance and fuel economy) are had with either of the 2 Magnaflow cat-back systems (3" single or their SIDO), and there you’ll probably see 0.5 mpg to maybe 1.0 more mpg. That's actually a lot to ask of a cat-back exhaust system in the 1997 & up F-150, to get another 1.0 mpg in a 2.5-3 ton truck.

At any rate, I've gone on too long again off-topic – give us a call to go over any of this in more detail, & best of luck whatever you decide!