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Discussion Starter #1
Im to the point where im ready to tune my truck for a little bump in power or regear it to gain some highway towing power.

My highway speeds are 65-70mph TOPS, most roads here limit me to 60mph being my max. One good thing about DE i guess.

Anyway, with that in mind, 4.56 gears with stock 34" tires gives my truck a spot on match to the towboss 350's with the 4.30's and with my current 35's im still geared a little taller.

The reason im torn is adding power adds heat and extra strain on the engine and trans. Reliability is of utmost importance more than anything.

But based on how underwhelming the towing power is at the moment with the 3.73 gears when i get into hills pulling my car, i have to do something. if i was pulling my old enclosed trailer, id be absolutely pedal to the floor to maintain 55mph up hill which is pretty pathetic imo.

The stock trans tuning is garbage for towing on the highway, stupid thing shifts into OD at 65mph which is around 1500rpms which as soon as it sees a hill it will downshift and usually drop another gear to maintain 65.

So, anyway, i did the math, im 2k rpms at 65mph and 2200rpms(stock tire height) at 70mph with 4.56 gears which for towing is perfect imo for stock tuning.

OR should i tune it and see how it does before spending 2500 to regear and rebuild my axles? But considering the cost of studs and potential additional trans wear, the cost isnt so high thinking long term.

thoughts?

Jason
 

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4.56s would be too low, even with 35s. 4.30s would much better suit your needs, and to be honest I wouldn't go any lower Than 4:30 unless your gonna run 37+. For me the first mod I did was 4.10 gears and beefed up differentials (check sig), boy what a difference it made especially off road.

Doing 4.30s and Detroit locker/truetrac will set you back at least $2500. You can do a nice tuner, intake, etc for that coin, you'll also have 1 tire fry when you over power the stock Trac lok:Rant:

Most guys just add a tuner and exhaust and be done. But when you do tuners, exhaust, supporting mods, and 4:10-4:30 gears with close to stock tires...that's when you have a big smile on your face:D

I haven't once regret the gears:wink[3]:
 

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Discussion Starter #3
Yeah, at first thought i also was like..damn 4.56's are a ton of gear but its a spot on match to a tow boss 350 on stock tires if i tow with the OE 34's.

No love for a one tire fire? LOL

Jason
 

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The 4.56's will work well for what you are asking but so would 4.30's with a decent tow tune. That is the route I would take myself looking at your goals.
 

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I have 4.30s with 35" tires and it's great all around, but get over 65-70 on the highway and it starts guzzling diesel because you're over 2k rpm at 65. My next tires will be 37s since I don't tow often.
 

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you are wooried about a litle extra heat and wear...why ? with stock long blocks making xxx power and being abused, they survivie pretty well. if you are that cautious to your engine vitals , this should be an easy fix. add some fuel to it, make the power and watch you gauges, seems very easy and relatively cheap compared to changing gearing front and rear, and having mileage loss issues for the remainder of the time you own the truck.
 

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I changed from 3.73s to 4.30s with 35" tires before and after. Engine and transmission work a lot easier now and mileage actually went up a hair. The key there is keeping the RPMs under 2k, which is 65mph with my setup now. Speed limit in Oregon is 65, so that's fine with me. I usually run 68-70 on the highway and get 17 mph with 4" lift, 35s, and 4.30s. Highway mileage didn't really change, but city mileage went up about 0.5 mph.
 

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I changed from 3.73s to 4.30s with 35" tires before and after. Engine and transmission work a lot easier now and mileage actually went up a hair. The key there is keeping the RPMs under 2k, which is 65mph with my setup now. Speed limit in Oregon is 65, so that's fine with me. I usually run 68-70 on the highway and get 17 mph with 4" lift, 35s, and 4.30s. Highway mileage didn't really change, but city mileage went up about 0.5 mph.

That's some good numbers.

4.56 is PRETTY deep. For the cost I'd drop it all to keep the temps down and add power.
 

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Discussion Starter #9
4.56 is very deep, but the RPM's that im towing at isnt where the power is which is my issue. On flat land its no biggy, but when i leave the state im pulling through the hills over the "mountains" we have here on the east coast and im having to wind the thing out up most hills pulling down 3k to 3200 rpms to maintain 65. While the power is there, i just think the original truck wearing 31.7" tires is the match to the powertrain with 3.73 gears.

I also tow city driving 5 days a week with my work trailer to taller gears will in theory help keep my trans temps down.

Just wondering if anyone else has gone as crazy as 4.56's. Sounds like 4.30's might be a good compromise.

And again, my rig is work truck first, toy a distant thought, so reliability is my primary concern since it is just a tune away from tearing up any hill on the east coast, but at what cost long term? Which is my primary concern. Gearing is cheaper than having to tear the truck down to stud it, or tear up the trans with my right foot, etc.

Jason
 

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The 6.0L likes to rev, 3k-3300 is just fine for pulling hills. Its actually easier on the engine than lugging up the hills at a lower rpm. The transmission control will put it in the gear you need to pull the hill most effectively given the throttle input and load. Peak torque is at 2k, peak hp is at 3300.
 

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Discussion Starter #11
Yeah, the gear change would put me at 2200 at 70mph which is perfect for towing on the flats, and when in the hills, droppin into locked 4th puts me around 2900rpms at 65mph which is just about right in the hills.

For reference, 4.30's put me at 2100rpms at 70 and 2750 at 65 in locked 4th.

This is for towing on stock 34" tires. Numbers are 75-100rpms lower with 35's.

Jason
 

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I vote 4.30s had them in my 2010 V10 great all around gear. 4.56 gears will really suck down the fuel at highway speeds, forget running down the interstate at 75mph. I use to drive a F450 for work and its absolute top speed was 84 mph that was with 4.88s though.
 

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I would love to regear my 250. I've always thought it would be better suited with lower gears

Can you get 4.10s for these trucks? It's a choice in the axle code but I'm not sure about the specific vehicle
 

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i'm confused, do you have 3.73 or 4.56's? from what i read you have 3.73's, and want more as$ in your truck. but like stated above 6.0's like to downshift. alot. and when they do your gonna wake the neighbors, but as bad as it sounds when it does it, it's better for the truck in general. one quick fix is to give the truck more power, (cystom tow tune) so that it has more power on tap to use making it work less to tow what you want it to tow. (following the more power means better mileage rule) because the truck doesnt have to use as much power to get moving.
 

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I'm telling ya man...get the 4.30s with the 35s and you'll pull that weight up mountains all day long. Although 35s are not the most ideal size tire for towing heavy loads...Gears make a world a difference when it comes to towing up hill. On my old '04 powerstroke longbed, I had 4.30s with 33" tires with Detroit lockers, and a tow tune, damn thing was a stump pulling machine and I pulled anything I needed to including a 30k front loader loaded on a gooseneck in Texas panhandle...yeah I know I was a DOT nightmare:D

Do a gear change and you'll never look back!! These trucks should've come from factory with 4.10s like the dodges
 

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Yeah, you really don't want lower than 4.30s with 35" tires if you have the 6.0L. Maybe with a gasser, but not the diesel.
 

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i run 4.56s and 37s. right now my 37s are bald and measure at 35 inches! It runs fine, but runs high rpm if i gotta do fwy. wouldnt go over 75mph unless i really pulled some rpm. I tow as heavy as they get, and wouldnt go 4.56s on 35s. As the tires wear down you gearing goes up more! but you are right, the towboss, the F450, duallys, they all come with 4.30s on stock (31.4") tires, which equates to 35/4.56. But those trucks are more work truck then "all around" truck. You say you drive it 5 days a week, probably dont want to be in work truck category. Bottom line is it would work, and would tow nice! but you not going to be happy if you on the fwy much
 

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Discussion Starter #19
Well, thats where i'm pretty lucky since DE has no freeways where i need to cruise at 75+. If i do, i dont take the big truck. Basically, if i leave state, im pulling my car. Otherwise, im in state and half the time i have 5k hooked up in low speed city driving.

90% of my trucks life is spent under 60mph.

Jason
 
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