MIKE,

I HAVE A 98' F-150 WITH THE 4.6 LITER. I HAVE A LIFT KIT AND 35" TIRES. EVER SINCE I HAVE PUT THE NEW TIRES ON WHEN I DRIVE DOWN THE HIGHWAY MY TRANSMISSION IS HAVING TO DOWNSHIFT CONSTANTLY BECAUSE OF THE ADDED TIRE MASS. I DO KNOW THAT IF I PUT NEW GEARS IN THAT WILL FIX THE PROBLEM BUT THAT IS PRETTY COSTLY. WILL A CHIP OF A PROGRAMER BE ABLE TO CHANGE THE SHIFT POINTS OF SOMETHING OF THE OTHER SO THAT MY TRANSMISSION ISN'T WORKING OVERTIME? ALSO CAN I FIX MY SPEEDO?

THANKS.

 

Hi M,

Tire "mass" isn't the problem, it's the tire *size* which has killed your torque multiplication, thus your performance, mileage, speedo, odo & shift points are all out of whack.

The additional mass is the least of your problems though that is something to consider, increasing unsprung weight does have a negative effect on handling and braking (yes, the additional weight does put a bit more load on the motor, but moreso to the automatic transmission), so better sway bars should be used as well.

The only way you're going to get what *I* would call good performance with 35" tires is to install the required 4.56 gears, as well as doing some bolt-on mods to get power up.

This is the single biggest mistake people make in these trucks, putting huge tires on without considering the consequences (and sometimes vendors selling the giant tires don't warn their customers, sometimes customers ignore the advice they're given, it's a big circle), which are, lousy performance and fuel mileage, along with the speedometer, odometer & shift point problems.

Now, for some people, and you may be included in this group, the additional 8%-12% power at any throttle positon or rpm from the Superchip tuning is enough to allow them to get what they feel is an acceptable level of performance. So a lot of people do that, and can thus hold off a gear ratio change until they can better afford it, while some *never* do the gear change.

You have a 1998 model, so the speedometer correction is not done by us in the PCM, it's done by simply installing the correct speedo gear in the tailshaft of the transmission, a $20 and 10 minute simple job. Correcting the speeedometer will help the shift points *some*, though we may need to do some custom tuning in the Superchip for your shift points, and I'd say to count on that.

The Superchips tuning is not going to take the place of a $1200-$1500 gear change on a 4X4, that is the only thing that will "fix" the problem of your engine not turning enough rpms to be in it's power band with those 35" tires & stock gearing. But it may give you enough of a performance improvement so that you can live with it.

The moral of this story is NEVER install tires of 34" or taller unless you are also going to do the required gear ratio change to get the engine back up into it's power band, the two go hand-in-hand.

If you'd like to have us provide the appropriate Superchips tuning to get you more power & take care of the shift point problems, etc., please give us a call & we'll be happy to go over this with you, our contact info is just below.

 

MIKE

WOULD YOU BE ABLE TO SUPPLY A GEAR FOR THE SPEEDOMETER? HOW MUCH WOULD A CHIP FOR MY TRUCK COST? THANKS FOR ALL THE INFO.

 

Merriman,

Caps mean you're yelling. Call Mike at his # listed. Prices can't be listed on the forums, it's against policy. But look at his link and it will tell you what you need to know as well.

John

 

Hi Merriman,

No, we don't directly supply the speedometer gears, but you *can* get them directly from any Ford parts counter, quick & easy! They're under $20, and you'll just need to know how many teeth you'll need on the new gear. That is determined by knowing exactly how much speedometer error you have, (in terms of a percentage%), and applying that percentage to the number of teeth on your current speedo gear. Then order the gear with the number of teeth you need, and it's a simple installation.

With regard to pricing issues, as John mentioned in his post it is against the rules here at F-150 Online to discuss any specific parts pricing, so you'll need to contact us off the boards for that information. We also have an online ordering system here which you can access just by clicking on the link to it just below in our signature line, so that info is easy to find.

Just so you'll know, as John was talking about in his post to you, when you type in all capitals anywhere in cyberspace (like in email, or on message boards like this, etc.), it is considered SHOUTING. Just FYI, no big deal, it's something most of us had to learn when we first started going online with any real frequency & communicating with others via online methods, etc.

What you might want to do is to give us a call & we can go over all these details with you, how to calculate the # of teeth needed on the new speedo gear, pricing on the Superchip product(s) and any custom tuning/programming needed, etc., we'll be happy to help you with all of that.

 

Mike,

Thanks a bunch for your help. I will be giving you a call here in the next couple of weeks when I get some money and I'll get that chip from you. I never picked up on the idea that caps means shouting, quess i didn't pay close enough attention. I have actually been a member on this site and another for two years. Sorry if caused any trouble.

Thanks.

 

Hi Merriman,

Don't worry about a thing, it's no big deal at all, just letting you know. Years ago, I used to type in all caps too, in my case because I felt it was much easier (especially on those old manual typewriters) not having to shift the carriage up & down, so it saved a significant amount of work & time! Actually, the only reason I ever learned to type properly (well, kinda-sorta "properly") was because I needed another class, and it was an easy credit hanging out with all the pretty girls in typing class.

Have fun & talk to you soon!