Truck gearing question.

[STLfirewood]

There are a lot of smart guys on here so I'll ask this question here. I have a 1999 F-350 V-10. It has 3.73 gears. It's an auto with overdrive. I have thought about swapping the grear to a 4.30 or a 4.56. I don't drive the truck fast. I only go up to 60mph right now. Usually I keep it around 55. When i oput the chip box on and pull the chipper it kicks me down to second gear on hills. Chipper weighs 6k. The truck doesn't get anything for mpg right now. 6-8 mpg with chipper and chips. Would a lower gear help my MPG at all with the slow speeds that I drive? I know it would help with power. This truck is only driven when it's being worked. I'm not worried about long distance or high speeds.

Thanks Scott

 

[danrclem]

I think that it would be guess unless you found somebody with a comparable truck with the gear ratios that you are talking about.

It may be apples to oranges but i have a 24' motorhome with a 460 and 4.10 gears in it but it doesn't have overdrive. It probably averages around 8 mpg but most of the driving is on the expressway.

I ordered a new '88 heavy duty F-250 with a 351 Windsor and 5 speed manual in it. I let the salesman talk me into 3.73 gears instead of 4.10s. I regretted that decision the whole time I had that truck.

 

[bushwackr]

the lower rear will be alot nicer for getting a heavy load rolling ,and it should make the truck feel peppier. Im sure that it will raise your cruisin rpm in turn lower you mileage , it may not be much but it will. I would go 4.11, I went 4.56 in my 3/4 ton and 55 mph is turning about 2800 rpm, I have no od tho, but it will raise some. Unless you have oversized tires,it prob wake the truck right up.

 

[chipherder]

Going to 4.30 or 4.56 should be much easier on your truck if you are pulling a 6k chipper, although as has been stated, mileage will drop a bit. You didn't mention whether your truck has overdrive or not, but it should get into third with those gears.
For what it's worth, I have an '06 3/4 ton Dodge Cummins, 6 speed stick with 4.73 gears, turns 2100 rpm at 60 mph.

 

[STLfirewood]

The tires aren't really over sized. The are 235 85 16's. I don't cruise on the hwy much. And when towing I take the overdrive off. I cruise around 1800 when doing 60 with the OD on. And I'm around 22-2300 with it off. I was thinking with the lower gears I could keep the over drive on and have the same cruise speed compared to the over drive off. But when it kicked to 3rd it would be better then before.


Scott

 

[dave_dj1]

the jump from 3.73 to 4.30 or 4.56 will be hardly noticable. 4.56 more so but still not a huge jump. 4.88 you will notice. Search the web for gear calculators, you just have to plug in your known numbers and it will give you a rpm/speed chart.
They used to have a chart on 4wd hardware that listed gear ratios and rpm's.
I have regeard some jeeps, the first one I went from 3.07 to 4.56 and then stuffed 33" tires on it, noticable power change. The next few I went straight to 4.88 gears, much better, I could cruise 55-65 in 5th gear running 36" rubber.
If you decide to regear, go to at least 4.88 gears. I'm surprised that a truck your size only has 3.73 gears in it to begin with.
Are you planning on doing the installs yourself? It get's pretty expensive to have them done. Time consuming as all get out!
Good luck, maybe shop around and see if you can find a junkyard that has an axle with the gears you want, might be cheaper/easier to swap the whole axle.

 

[Circle B MN]

A two wheel drive truck, especially one like I assume yours is with a floating axle, can have the gear swapped in about four hours if you have some experience. Front may take a little longer depnding on the setup as it is often more involved to get to the gear.

And As a general rule, never jump up just one gear size. Two is a minimum.

 

[IthacaMan]

Im thinking that for what the gears and install is going to cost,it is going to take a while to pay for itself.Maybe a less restrictive exhaust and a K and N airfilter would be cheaper and give better results.Just food for thought.:msp_unsure:

 

[jerryw66]

I like the 4.10 or 4.30s a lot more than the 3.73s. The difference isn't much, but I can tell, more so when towing things. If you do switch gears, it would be a good time to put in trutrac or some kind of limited slip or locker too.

 

[TMFARM 2009]

There are a lot of smart guys on here so I'll ask this question here. I have a 1999 F-350 V-10. It has 3.73 gears. It's an auto with overdrive. I have thought about swapping the grear to a 4.30 or a 4.56. I don't drive the truck fast. I only go up to 60mph right now. Usually I keep it around 55. When i oput the chip box on and pull the chipper it kicks me down to second gear on hills. Chipper weighs 6k. The truck doesn't get anything for mpg right now. 6-8 mpg with chipper and chips. Would a lower gear help my MPG at all with the slow speeds that I drive? I know it would help with power. This truck is only driven when it's being worked. I'm not worried about long distance or high speeds.

Thanks Scott

ok, this is right up my alley...lol
my f-250 runs 373's and yes it is a bit of a dog with serious loads on,,,, that said
personally i would drop tire size first.
235/85r16's are a tall tire thus taking more horses to pull at speed... i would recommend dropping to a set of 245/75 r 16's and try that first.. it will drop the height of the tires about 1 1/2 " so giving more horses at speed..should not drop fuel mileage a bunch like switching gears would..and at a fraction of the cost..
buy a used set from junk yard preferably already on rims that fit and try them first..you will be amazed how big a difference it will make..
also you should not tow that heavy a load in overdrive, it can tare out the trans... we do this swap a lot for farmers around here at our shop..:msp_smile:

 

[Huskybill]

My 76 one ton Chevy 4x4 truck I built had 4:10 gears with a locker in the rear and a locker in the front. With a th400 with the extra low first gear and 2800 stall converter. With a 400hp 350 sb. She had plenty of power even with 1 1/2 cords of firewood in the back. I pulled out of the gravel pits once with 16k of 1 1/2” stone. When I changed it over to the granny four speed it had less power.

 

[Husky Man]

2 wheel drive or 4?

What is your gross combined vehicle weight with the truck loaded with chips and the chipper coupled behind?

A gear vendors auxiliary transmission with Underdrive/Direct Drive might be a good option to consider.

An Aux Tranny my not be your "Cheapest" option, but may give you the Best Results for the money spent

You would still have the same drivability you have now, plus a second lower ratio option as well

The Gear Vendors Aux Trannies have been used for many years in the LARGE RV market, and the "Hotshot" Expedited transport market.

I have never had or used a Gear Vendors Aux Tranny, but know that they have an Excellent Reputation for Durability and Performance, it would be worth looking into

Doug

 

[Marley5]

I was all ready to respond as I'm familiar with gear swaps but saw how old this thread was.

 

[Husky Man]

I was all ready to respond as I'm familiar with gear swaps but saw how old this thread was.

Schitt you're doing better than me, I missed that

Doug

 

[Huskybill]

I had 16 leaf springs in the main with 10 in the helper in the rear, ten leafs in the front. That’s 72 leaf springs in the 8” wrecker frame. She never leaned.

 

[spyder62]

Grits Gresham

 

[Huskybill]

Almost rolled the front end in a off camber situation off road with the std 6” lift kit springs. I stacked them up to ten on each side in the front and it was steady off road after that. Being a small time firewood guy just starting out I need to get the truck to the wood it’s less work.

 

[DSW]

By this point I'm sure he ditched the v10, swapped in a 7.3 and stopped worrying about things like....gears.

 

[ChoppyChoppy]

My 76 one ton Chevy 4x4 truck I built had 4:10 gears with a locker in the rear and a locker in the front. With a th400 with the extra low first gear and 2800 stall converter. With a 400hp 350 sb. She had plenty of power even with 1 1/2 cords of firewood in the back. I pulled out of the gravel pits once with 16k of 1 1/2” stone. When I changed it over to the granny four speed it had less power.

I was sitting at 22,000lbs 2 weeks ago with a load of gravel, right around 7.5 tons of gravel in the bed. 160hp small block and 4 speed. 4.56 gears.
Dumped it fine, I think I've loaded it heavier with dirt at the shop, have had it not want to dump before!