Been driving my truck with it lifted and new tires and wheels for just under a year now. I love it and wouldn't change it back for anything. I pulled my TT down to S. Padre last week. Last spring I lifted my TT 4" as it was too low to start with and it pulled great. The truck pulled the TT better than stock. We went 4 wheeling every day on the national sea shore and the truck never had a problem getting through anything we put it through. We even went at full tide and saw only 2 other 4x4 and were stuck in the sand. Wanted to help but they didn't want it, they had a tow truck on the way. So needless to say, we were the only ones driving up and down the sea shore. It performed flawlessly, just what I built it for! Now to my question.

1. While towing the TT I had trouble with the trailer tow, My speedo is off by 12% and doing 70mph shows on the speedo at 62mph. I was only able to get in overdrive very little. I noticed that if I got the speedo to show 70mph then it would go into overdrive, but thats doing actually 78mph. Most of the time I keeped the speedo at 56mph which is 63mph but it would stay in 4th gear running at 2,200rpm.

2. Would it be better to use Truespeed and correct my speedo for the pmc to shift properly? I like the fact that I don't put as many miles on my truck as I really do, but not that big a problem.

3. With a tuner, would it help in the shift points? I really am not looking for more power as the truck pulls fine. And don't really want to screw with my warenty.

4. I had lots of power pulling the TT. I would see another TT up the road and get closer, notice that it was a Dodge or Chevy and pass them with a grin on my face.

So does anyone have any insight on the Truespeed or a Tuner. If I went with a tuner I think I would lean towards SCT as I've heard great things about them. But I really don't want to add gauges and new exhaust right now.

Thanks for any help, Texcan.

 

You need to at least program the truck computer for the size tires & gears that are in it. This way it will shift correctly.

I have been told that 36" is as high as the imput will allow, but this should put you back in the stock operating range for the transmission. The 1" difference would put you back close to actual speed, or at least then it would be off consistant with stock tires.

I cannot remember what the lowest gear ratio available stock is (3.54?), but 3.73 seems to be the middle, with 4.10 & 4.30 also options. I have been told the computer gets its speed reading off the ring gear (tire rotation).

How does the computer compensate for the variance in gear ratio extremes...or does it?

 

SCT's Xcal to or Superchips Inc Flashpaq is that you need.

 

When I got the lift and tires, I took it to the dealer and tried 3 times with them to recalibrate the computer for the tires I have. They finally called ford and ford told, them the biggest tire was a 35" so they left it the way it was. They told me to buy a tuner to fix my speedo. The truck runs fine without the TT and I don't need anymore power. I really don't want to mess up my motor. It's been the best truck I've ever owned. But if a tuner will help me with the shifting while towing then, that maybe what I need to do! But I'm still not convinced that is the best option. I hear stories of head bolts and other things going wrong with the 6.0 when a tuner is added.

 

Grab a flashpaq 1805, load in the tow program (very conservative), and recalculate for gear and tire.

If you do this, you will wonder why you ever second guessed this option.
It should also reward you with increased fuel mileage.

 

beemr...for the F-250, 3.73 is the highest ratio available. The Diesel E-350 van has a 3.55. I tried to find out if those gears would fit in a F series.

I have stock wheels and 85 series tires for milage and would like to put in the 3.55's if it would work. Total opposite of what normally is said on this site with guys and their raised and over size tires. To each his own.

I tow some and don't use my truck for a daily driver. To me a diesel with this much torque should be able to cruse down the hyway at 70 at about 1700 RPM not 2000.. If I ever find out if this would work and they could reprogram the trans for the higher ratio; I believe at lot of guys on this site would do it....Good Luck to all

 

Jimmy,

Remember its load, NOT engine RPM that determines fuel mileage.

The calulated engine load is more often than not greater at 1700 RPM with 3.55 gears than it is a 2000 RPM with 3.73 gears.

This is why many of the higher fuel mileage vehicles have more aggressive gearing.

The most fuel effiecient powerstroke I've ever encountered has 4.88 gears.

I can go into a HUGE discussion regarding this, but have done it a few times already, so search my old posts.

 

When I ordered my truck, I had the option of 4.10 or 4.30 gear ratios.

 

Get the Truspeed . Very easy to install and you can dial in your tire size were YOU want it. Alot of stock trucks speedo's are off from the factory and with the Truspeed you can change it anytime anyplace you want. You can remove it from your truck when you sell it and install on differnt truck with no problem. PM me if you want more info on it. I installed one on my truck and glad I did and didn't want to play the warranty game with a programmer.

 

Many F450 and F550's offer 4.88's

 

I second the TruSpeed. They can be had for around $160 on the internet. Very easy install. You pick a mounting location, run the wire, unbolt a couple of screws and a plastic clip on the drivers side fenderwell, pull down the wheel well cover, splice into the ABS harness and then calibrate with a GPS and you're done.

 

Well if a tuner can help then, what if I go and try the bullydog and see if it will help. They have a try before you buy. As I understand their's will adjust for tire sizes. Then I can see if I like the extra power. Has anyone ever tryed this before? Do you have to go back for them to change it to stock? Or does it just last for a day or so? Will I need to worry about hurting my truck? Like to hear from someone who has tried this. Did you like it so much you went and bought one?