Adding gear vs adding power... - Ford Powerstroke Diesel Forum
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  #1  
Old 09-03-2012, 05:46 PM
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Adding gear vs adding power...

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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Old 09-03-2012, 06:16 PM
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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

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

I haven't once regret the gears
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Old 09-03-2012, 06:19 PM
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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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Old 09-03-2012, 06:29 PM
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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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Old 09-04-2012, 08:06 AM
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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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Old 09-04-2012, 08:54 AM
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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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Old 09-04-2012, 09:20 AM
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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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Old 09-04-2012, 03:09 PM
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Quote:
Originally Posted by cartmanea View Post
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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Old 09-04-2012, 03:20 PM
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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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Old 09-04-2012, 04:02 PM
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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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