to much tire?
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Senior User
Joined: Sep 2003
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From: San Jose NOR*CAL
to much tire?
Forgive me if I'm in the wrong forum, here is my question/problem
I had my F250 4X4 lifted 4" and was able to score some Bfg 315 75 16 mudders for free. It has a 5speed w/ over drive and 3.55 gears.
On the freeway (flats) it drives fine , but she "dogs" it on the hills.I plan on pulling a 14" travel trailer to Pismo Beach and I was thinking of re gearig her.
I want to keep highway speeds , and be able to pull on hills I know that my beast gets bla mpg so I dont want to lose any fuel economy.
What gears would be best?4.55 4.10?
I had my F250 4X4 lifted 4" and was able to score some Bfg 315 75 16 mudders for free. It has a 5speed w/ over drive and 3.55 gears.
On the freeway (flats) it drives fine , but she "dogs" it on the hills.I plan on pulling a 14" travel trailer to Pismo Beach and I was thinking of re gearig her.
I want to keep highway speeds , and be able to pull on hills I know that my beast gets bla mpg so I dont want to lose any fuel economy.
What gears would be best?4.55 4.10?
Fleet Mechanic
Joined: Aug 2003
Posts: 1,548
Likes: 46
From: Kemmerer, Wyoming
You are definitely geared wrong for those tires... that size is the equivalent to a 34.6" tire. Were it my truck, I would stick some 4.56s in it. That would give you 2900 rpm @ 65 mph in 4th gear, 2300 rpm in O/D... right in your 351's powerband.
A big block would do well with 4.10s, but still too tall for a small block IMO.
A big block would do well with 4.10s, but still too tall for a small block IMO.
Fleet Mechanic
Joined: Aug 2003
Posts: 1,548
Likes: 46
From: Kemmerer, Wyoming
Right now I can only guess, because I don't know what your stock tire size is.
However, I can tell you from experience that having the engine work too hard (like yours is now) can actually hurt your mileage.
My truck is a good example... I bought it with 33s, 3.50 gears, and a 300 I-6. It got @10 mpg, and had no real power to speak of. I put in the 390 (known to be a gas hog) and I actually got better fuel mileage... @12 mpg. But, the 33s were still too tall for my 3.50 gears, and I could really tell it when I was towing something.
I swapped in 4.11 gears, and the truck really came to life. It pulls MUCH better now. The best part? My mileage is exactly the same, maybe a little better... @12-13 mpg.
I believe that if you're concerned about fuel mileage, you should go w/ 4.10s. But, the 4.56s will give you a little better power, and might not really affect your mileage all that much.
There are others on this forum who would argue with this, I'm surprised to see they haven't added their $.02.
At any rate, good luck and let us know what you decide to do and how it goes!
However, I can tell you from experience that having the engine work too hard (like yours is now) can actually hurt your mileage.
My truck is a good example... I bought it with 33s, 3.50 gears, and a 300 I-6. It got @10 mpg, and had no real power to speak of. I put in the 390 (known to be a gas hog) and I actually got better fuel mileage... @12 mpg. But, the 33s were still too tall for my 3.50 gears, and I could really tell it when I was towing something.
I swapped in 4.11 gears, and the truck really came to life. It pulls MUCH better now. The best part? My mileage is exactly the same, maybe a little better... @12-13 mpg.
I believe that if you're concerned about fuel mileage, you should go w/ 4.10s. But, the 4.56s will give you a little better power, and might not really affect your mileage all that much.
There are others on this forum who would argue with this, I'm surprised to see they haven't added their $.02.
At any rate, good luck and let us know what you decide to do and how it goes!
Postmaster
Joined: Jul 2003
Posts: 2,711
Likes: 2
From: Pittsburgh
With the o/d you can't really go too deep with gears (wthin reason). 4.56's would be nice, might even look at 4.88's depending on what speed you like to cruise at on the highway. Deeper gears make for better around-town mileage (to a point) and worse highway.
Justin
Justin
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Senior User
Joined: Sep 2003
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From: San Jose NOR*CAL
hoxiii thanks for the info too I do about 50-50 driving (highway and city) with an occasional trailer tow.
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From: San Jose NOR*CAL
Here is my update. I went with the 4.10's. I am very pleased with the swap. I have my old power back! as well as my MPG.
I have a "test hill" ( the Sunol Grade I 680 ) that I used to gauge it. It climbed it with ease were as before it chuged along and it lost power 1/2 way up.
Thanks for the input and help.
total cost $1065.00
help from FTE fourm.... priceless!
I have a "test hill" ( the Sunol Grade I 680 ) that I used to gauge it. It climbed it with ease were as before it chuged along and it lost power 1/2 way up.
Thanks for the input and help.
total cost $1065.00
help from FTE fourm.... priceless!
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