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Thread: Truck gear change question

  1. #1
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    Default Truck gear change question

    Truck is a 2002 Ford Super Duty 4x4 diesel with the 4 speed OD trannie and I believe it came stock with 3.73 gears. Been giving some thought to having the gears changed out to either 4:10 or 4:30's to help the towing performance.
    It does "ok" when towing our Sea Sport now but does feel a bit sluggish hence the possible gear swap. We never drive over 60 mph when towing and usually hold to 55 so the higher cruising rpm shouldnt hurt the mileage at all. Currently getting about 11-11.5.

    Has anyone here personally had a local shop do a gear swap out? I know swap outs can be tricky due to shimming them properly so am looking for first hand information.
    Tennessee

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    Member Dupont Spinner's Avatar
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    I have the 4.10's in my '05 with the 6.0 and at 65 mph I am running right about 2100 rpm's, which should put your 7.3 in it's big toque range at 55mph. That 11 to 11.5 mpg is towing I hope? The 4.30's would be way overkill. I have a friend with the F450 and the 4.30s and empty he is begging to see 10 mpg and he is running in the upper 2g's for rpms at highway speeds.

    The only shop that I would recommend for the swap is Young's Gear. These guys really know their stuff. Make sure you have your truck reprogrammed for the gear swap. Remember that the speedometer runs off the ring gear making the swap sorta pricey.

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    Gearing down will have a negative effect on your fuel econmy every single day. I drive a 99' F250 SD 7.3 with 3.73 gearing and have never been disappointed in it's towing ability. Keep in mind also that both differentials would have to be changed out . For the cost involved you may get more satisfaction and performance by allowing the engine to breath better, ie; new exhaust and intake along with a tuner chip.

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    11 - 11.5 is towing. Truck also has a 3 inch exhaust. Empty we average 18 running between ER and Anchorage in the summer. Am going to have to do some calculating to see what the rpms would be with the current tire size with the 4:10's and 4:30's at 55. Will have to make a trip to Youngs when I get some time to discuss this.
    Thanks
    Tennessee

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    +1 on youngs gear on international airport rd. those guys will either sell you the right stuff or do the work for the best price in town.
    Life is not a journey to the grave with the intention of arriving safely in a pretty well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming-----WOW-----what a ride!
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    For you folks recommending Youngs, what work did you have them do for you?
    Tennessee

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    rear bearings and seals.....have gotten parts for various other projects from them also, always helpful for the my do it myself stuff.

    Any reason you don't just push the button and keep it out of overdrive. That would net you pretty close to the same as a swap to 4.10. It would only be about a 300 rpm difference as I am calculating on stock tires.

    I have a gas truck with 4.30's and no overdrive that thing is screaming at 60 mph. I see if I can borrow my buddies truck with the 4.30's and take you for a ride.

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    Randy, typically the RPM's on those trucks with STOCK TIRES at 70 MPH are...
    4.10's 2400 rpm's
    3.73's 2200 rpm's
    3.55's 1900 rpm's

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    Quote Originally Posted by Snowwolfe View Post
    For you folks recommending Youngs, what work did you have them do for you?
    My truck needed a u-joint and napa or schucks didn't stock it. I went and bought one at the dealer for 110.00. I didn't have time to change it so I stopped at youngs to find out if they could put it in for me. I told them the whole story and the guy behind the counter said we will put it in for 75.00 and throw in a u-joint, so take that one back. I left smiling.
    Another time I had a vibration they test drove it changed my transfer case fluid put in a carrier bearing for 280.00.
    Life is not a journey to the grave with the intention of arriving safely in a pretty well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming-----WOW-----what a ride!
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    i have a dodge 12 valve cummins with 3.55 gears and in stock form did not pull real good when i would hook up 20k behind it i tow round bails of hay to solodtna alot. so i too thought about lower gears but i just bumped up to the power to about 350hp or so and now i get good milage and losts of power to pull the hills i can pull any of the hills from wasilla to soldotna loaded at 50 mph or faster with a full load of 17 round bails.

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    2000rpm in my 99' with stock tires and 3.73 gears is 72mph.

    As for Young's Gear I have done business with them for many years and have always had positive experience, both as a shop owner and mechanic otherwise since the time they opened their doors. I recommend them as well.

    The 3" exhaust is factory diameter, a 4" exhaust makes a great difference. Boosting engine efficiency and performance will be a greater improvement than the gearing... I promise

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    I recommend Young's Gear as well. When I was buying parts for the Air Force back a few years ago, I spent an ENORMOUS amount of money with them. We purchased from Dodge the Dana 70 shell axles and had Young's putting them together and then we were sending them over to Iraq and Afghanistan. These were going into 1996 Dodge 2500 bobtailed Age tow tractors. The best I can remember we had 0 failures on those, not to mention all the Spicer and Rockwell punkins they have built for us over the years. I think Justin is still running the counter down there and he's top notch.
    But I am like the rest that say power up a little bit and get a programmer or chip. It seems way more cost effective.

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    Quote Originally Posted by .338WM View Post
    2000rpm in my 99' with stock tires and 3.73 gears is 72mph.

    As for Young's Gear I have done business with them for many years and have always had positive experience, both as a shop owner and mechanic otherwise since the time they opened their doors. I recommend them as well.

    The 3" exhaust is factory diameter, a 4" exhaust makes a great difference. Boosting engine efficiency and performance will be a greater improvement than the gearing... I promise
    The speed sounds about right for rpms/stock tires. My 7.3 is pretty heavily modded for a long time so I wasn't exactly sure. Now on the exhaust....the down pipe is 3 inch and from there back is 3.5 inch. Many times just elminating just the muffler shows great improvements. Both my 7.3 and 6.0 I am running 4 inch turbo back.

    As far as other places for good info try this website.
    http://www.thedieselstop.com/

    One of the moderators does not live very far from you Snowwolfe. Also if looking at doing the exhaust, Northern Diesel Performance is also a very good choice. Call me or stop by.

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    The 3 inch exhaust was installed about 2 years ago. It did seem to eliminate some of the turbo lag but not much improvement in power. But the fuel economy when empty went up about 4 miles per gallon, but when towing it didnt change. Weird, eh?
    Anyhow, back to the gears. Will go talk to Youngs them when I get some free time. There is more than just a higher cruising rpm if the gear swap is done. If the only reason to change gearing was to raise the cruising rpm I could just click out of overdrive. Same principal of using low range when retriving the boat, effortless power going up the ramp.
    Tennessee

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    A friend has that same truck. It is a real dog and eats fuel. He wants to chip it etc...... just trade it.
    I don't mean to sound bitter, cold, or cruel, but I am, so that's how it comes out.
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    My 03 Excursion with the 7.3 in it has 3.73 rear end and if your getting 11 mpg your doing good. I burn 1/4 of a tank going to Whittier and back... No 11.5 towing is not bad in my opinion. Save your $$ on the gear change and get it chipped. I put a chip in from DPTuner and a valve body from Factory Tech. The difference is night and day. I have a 20 HP Tow and 40 HP tow setting as well as an 80 HP Economy program and it made me keep the truck. The valve body made the sloppy tranny shift like a truck transmission. A little extra HP will make up for the gears and cost you quite a bit less.

    On a side note, putting in chip and valve body in your truck is fairly easy and I would be happy to help you do it if you decide to go that way.
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    Something else to consider and some reference charts as well..............http://www.gearvendors.com/f2wd4s.html

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    Quote Originally Posted by dirtofak View Post
    A friend has that same truck. It is a real dog and eats fuel. He wants to chip it etc...... just trade it.
    Ain't gonna happen. We bought this truck new 10 years ago and it has 90K on it and is still on the original brakes. Zero repairs to date. Three trips down and back on the Alcan. Not going to spend another 30-40K to get the same truck with a little more power and then have to wash and wax the dang thing all the time and worry about it.
    I like the low insurance cost and the fact a ding doesnt bother me anymore. No more truck payments for me.

    JR2, might give you a shout soon.

    Off to PWS to chase blackies and shrimp. Ya'all have a good week.
    Tennessee

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    Good luck Randy on the shrimp and bear. We may see you out there as we're leaving Wednesday.

    I'd be interested to hear your experiences on the truck. I'm in the market for a diesel as we speak and have been thinking about a 7.3L Ford or the 5.9L Dodge. Good luck getting it figured out.

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    Quote Originally Posted by patrickL View Post
    Good luck Randy on the shrimp and bear. We may see you out there as we're leaving Wednesday.

    I'd be interested to hear your experiences on the truck. I'm in the market for a diesel as we speak and have been thinking about a 7.3L Ford or the 5.9L Dodge. Good luck getting it figured out.
    DO the 7.3, stay away from the 6.0....as for the Cummins, the 1st year of any upgrades need to be researched closely. I don't care for the truck, wish I had the engine instead of my 6.0.

    Randy, So from what I am reading is that you had the exhaust replaced? and a 3" was installed? That may where alot of the problem lies, especially if a stock or close to stock muffler has been installed. The stock muffler had a 3.5" inlet/outlet, but the tubes inside the muffer were only 1 3/4" and the exhaust had to travel back and forth inside before reaching the outlet.

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