Gearing?? Might be a touchy subject for a few - Ford Powerstroke Diesel Forum
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post #1 of 8 Old 07-21-2009, 03:07 PM Thread Starter
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Gearing?? Might be a touchy subject for a few

I was hoping to ask this question once these trucks have been run, lifted, and tuned for a while. I don't want to reignite another epic battle over this topic, those involved will attest, Pahrump and Wildcat. Ok, enough poking the bee hive and to my point.

I, like several, have lifted my 08 crew cab, put 37's on it and left the stock gearing at 3.73. With the 250 tune my truck ran 14.1 in the quarter mile with the 37's on and got down to 13.9 with my stockers on the hubs. I am sure rotating mass and diameter play a large part in this difference, not to mention that this was my first time at the track with the truck and reaction times may be relevant, but would be so in both cases. (Sorry, haven't gone with the 275 yet).

I have thought over and over about putting in 4.30s, which would put me back in the area of stock gearing with stock tire size. I am just having trouble coming to terms with the $2000.00 it would cost to purchase and install the gears.

My question is, has anyone with a similar set up run their truck down the track with the stock gearing and then re-geared.

What was the difference in time?
Was the expense worth the increase?
Any difference in fuel economy?

With my truck (275 tuned) I noticed that using my stock tires the converter would lock up at 50mph NO MATTER WHAT, and I loved it. With the 37's on the lock up would delay to 60 or 70 mph and sometimes wouldn't lock at all until I let out of the gas a little. It will lock up at 50 under light to moderate throttle but delay under moderate to heavy acceleration. I am sure this is from the added resistance of the larger tires and added mechanical (gearing) drag.

Just looking for some feedback and any time you guys put in to providing the info is much appreciated.

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post #2 of 8 Old 07-21-2009, 03:19 PM
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cheap bump

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post #3 of 8 Old 07-21-2009, 03:51 PM
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This site has all sorts of calculators that may be able to give you a little bit better of an idea what you'll be hitting at the end of the track as far as MPH and RPM. If drag rasing is of major concern why wouldn't you take the gearing further yet say to 4.56 or 4.88? I can't be much help to you as the stuff I can afford to play with is old, but can a manual torque converter lockup be made for the newer trucks? It's dirt cheap and easy for the old ones.

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post #4 of 8 Old 07-21-2009, 05:06 PM
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Originally Posted by Joel View Post
This site has all sorts of calculators that may be able to give you a little bit better of an idea what you'll be hitting at the end of the track as far as MPH and RPM. If drag rasing is of major concern why wouldn't you take the gearing further yet say to 4.56 or 4.88? I can't be much help to you as the stuff I can afford to play with is old, but can a manual torque converter lockup be made for the newer trucks? It's dirt cheap and easy for the old ones.
There is no cheap lockup for these trucks, you'll just piss the TCM off and it doesn't work. Matt's been getting the lockup under control quite well with the 310 tune, the job 2 and later's have been working great. Just got a new 310 for my job one F450 but haven't gotten to test it yet, maybe Wed. As far as gearing the 4.30's seem to work the best with 37's. I run that 4.30 gear with the 40" tires on my 7.3 (that had 3.73's stock). Evil is got a tough choice, the gears seem to help most when towing a trailer, not so much when the truck is empty. I think you find the 4.56 or 4.88's are going to be to much of a jump, unless your just towing.
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post #5 of 8 Old 07-21-2009, 05:32 PM Thread Starter
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Very True

Sean knows me too well and he knows that I have been stewing over this decision for a while now. Also, since he will be doing the work he is sensing that the execution time is nearing the final prep for launch is underway.

Sean also knows the topography of the land here in the northeast and that there is a lot of stop and go in addition to having very little flat land. That being said, gearing may complement my terrain.

I am probably being to idealistic and expecting someone to say "I got the same set up, I went to 4.30's and the truck runs just like it did with the stock tires on it." is not realistic. But being that way mostly leads to disappointment. Also expecting someone to admit to throwing out the cash and then admitting that they are a boob for doing it is another issue.

During the winter I take off my 37's and run the stockers thru the muck and yuck. If I re-geared this practice would be compromised

2008 F-350
8" ProComp on 38" Mickey Thompson ATZs
Straight Pipe with Magnaflow 5" No muffler
Downpipe by Powerstroker67
AFE Intake
Elite Headstuds w/upgraded gaskets
Spartan 350/Kem 345
Spartan TCM
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Pioneer AVIC NAV
4.30 Gears
Detroit Locker
Suncoast Converter
BD Diesel Blow Off Valve
Cold Side Intercooler Upgrade
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post #6 of 8 Old 07-22-2009, 05:52 AM
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4:30's in my 06 dually with the stock tires app 31.5 tall at 75 was 2500 rpm's, when I went to the 35's it dropped down to 2225 rpm's at 75. Maybe this will help you,,anything more than that is gonna kill you when running the stockers during the winter.

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post #7 of 8 Old 07-25-2009, 11:32 AM
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I ran 3.73 and 38's for a short period of time before wapping to 4.56's. It made the truck far more enjoyable to drive, especially when towing. For the last 10,000km's I've been running 37's. Honestly, its geared a bit too low for my liking when I'm unloaded, but quite often I'm pulling 15,000lbs. Then I'm glad I've got the lower gearing. 37's and 4.56 will net you about 73mph at 2250.

The other plus to re-gearing is the benefit to your transmission. Your tranny will live far longer, (lower operating temps) with the lower gearing.

If you're towing heavy and frequently, then do the 4.56. But thats the absolute lowest I'd go. If you don't tow that often then 4.30's will be better. Even 4.10's would be ok, but it would be hard to justify the expense to make such a small change.

Goodluck.
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post #8 of 8 Old 07-25-2009, 11:51 AM
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I am very happy with the way mine runs at the track, around town, and towing...course I dont tow over about 10-11K. 38s stock 3.73 gears, and I tow with the 275 tune, daily drive with the 310.

Truck will run consistent 13.4-13.2 times on the 38s@ 99-101mph on #2....

Runs 82mph at 2000rpm so course at 70-75 its lower..I see 18mpg give or take a hair on a highway trip.

2008 F250 FX4 CC SB Black on Black STOCK and SLOW...Rolled over and TOTALED...

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As far as actual HP numbers I have no idea. It don't snap your neck but.....It feels good.
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