my tires are considrered 35's but the actual size when calculated out is 34.6"
i would not go above 4.10's with stock tires. the gears i have now give me abot a 3.94 stock equivilent. the hypertech was great. really easy to use and noticed an improvemnet right away. i would recommend anyone with a 4.6 to do what i did with my truck. except for gears unless they have the tall tires. all i need to do now is exhaust.

 

The normal conversion for metric to english says the following:
Dewalt17 is running tires that are (about) 34.8".
Mac_app is running tires that are (about) 32.8".

Here is a link that will calculate out the tire diameter:
Tire Hight Calculator

Here is a link that will calculate out the mph/RPM/GR/RWdiameter:
Calculator for MPH, RPM, GR, RWDiameter

Ok now that we have addressed the tire hight/final drive ratio issue lets look at your setup:

* You have a stock tire on your truck (What size?)
* You have stock gears (What Gears ratio?)
* What is the total weight of your trailers with the sleds
and all the associated gear that you haul?
* Do you have stock brakes? (there are no trailer brakes on a 2 place sled trailer)
* What altitude are these hills taking you too? (For every
1000ft above sea level there is a reduction of ~4.5%
in air density ie. at 10000ft your truck only has ~1/2
of its original hp)
* Is your truck a 4x4 or a 4x2?

It really surprises me that you are having problems getting up hills with your truck

I haul my 3 place sled trailer up to rabbit ears pass (10,000- 11,000) without a problem. (3 sleds @ 550lbs each + trailer aluminum sledbed ~1000lbs) I did this even before I changed out the gears. So we are talking about ~2650lbs + fuel + gear = ~3000lbs. Really not a whole lot of weight here.

Suggestions/Options:
Put your sleds on your buddies trailer. cheap but you will get razzed.

Get your truck running at peak hp/torque in stock form.
Install a intake and exhaust.
Upgrade your brakes!!!!!!
Now start looking at gears and tires.
Remember big tires steal torque and you will have to
compensate with your gear ratio

Good to see another sledhead out there! [btw: what sleds do you ride]

If you want more detail on the calculations or what I did on my truck e-mail me I can go into more detail.

 

Thanks guys!
My tires 265-70-17 work out to about 31.6", basically stock tires and 3:55s on a 4X4. I have an aluminum 2 place, 2 duffles, oil, tools, wife and I, nothing out of the ordinary weight wise. I hadn't made it throught the RPM calculator just yet, but I'll get into it, I'm sure it's gonna provide some great info. My immediate issue is that here in Michigan, the highest elevation that's possible I believe is in the Porcupine mountains and I haven't been there. 2000 ft, not exactly what you're used to driving through I mean gentle rolling hills going to the upper penninsula, even some of the overpasses! Detroit I think is about 1000 ft. My shift points don't seem to be correct and I find the trans constantly downshifting and the RPMs are either too high (3000) or too low(1900 in O/D). I'm constantly taking it out of O/D and it screams up to 3K until I fiddle with the O/D switch, up shifts to 2500 or so and holds. If I go back to O/D, it goes to about 1900 or so and as soon as there's any kind of grade, It downshifts right back up to 3K again. Keeping up with the guys means about 75 to 80 at times. I'm suspecting the trans has an issue somewhere in the 3 to O/D shift or torque conv lock-up controls. I have to mention this experience was last year with BFG 285-70-17s at 32.7". The truck/trans seemed happier around town with the smaller Gdyrs back on it, but it looks like it's only a 1" difference. I've never been a big fan of how the stock Fords shift, but I think my issue is beyond that. Sometimes there seems to be a slight shudder as the O/D locks-up. I'll get the trans looked at and then tinker with addons. I like the 4.6, but if the trans isn't working correctly not much you can do. I was trying to figure out if this was normal or not and whether a chip or tuner might help me out of it.

BTW....I have a '99 AC ZL600 EFI and we just picked up an '05 AC Sabercat 600 EFI LX for my wife which I think she's gonna love.

I'll reply back with any results.

 

Ok, I didn't even think about shift points (I have a 5sp manual). You can change shift points with one of those Hypertech programmers. You might ask Dewalt17 how his works.

REMEMBER PEAK TORQUE FOR A 4.6 IS AT 3200RPM

If the truck is jumping up to 3000rpm it is trying to jump to its torque curve. This is what you want it to do. When pulling a hill I want to start the hill at around 2600-2700rpm and accelerate up it. This insures that I stay in the powerband where I have the most torque.

Based on what I just said I would look at your Transmission lock-up. Instead of changing your shift points go for a more positive lock-up on the shift. Don't be scared to run your RPM up to 4000rpm. I couldn't find anything that stated the redline for the 4.6 but before I changed my gears it was common to pull a hill at 4000rpm just to make it up. Now that I have 4.56gears its a piece of cake just to pull a hill at 3200rpm and accelerate all the way up.


[by the way nice sleds, I have 01' MM600, 03' RMK800, 99 RMK700 praying for deep snow this year]

I hope the information that I have provided has helped!

 

Thanks for the shift info. It's nice to have input that what seemed out of the ordinary, wasn't necessarily so. 3K seemed hi to me. Did I mention that I had a '97 F-250 7.3L PSD before this truck? PSD RPMs are much lower than that of the gas engines, low RPM access to mountains of torque. I guess I was very spoiled.

I'll continue my programmjing Qs in the chip forum.

BTW: Common love of a sport, although very different colors! I hope you get the deep snow those sleds deserve