does this sound right to you?
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Senior User
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does this sound right to you?
According to the tag on the diff, I have a 3.08 rearend. Doesn't this seem like an awful tall gear for a 90 F150 351/E4OD extra cab longbed? By the looks of things, it seems that a lot of people on this board refer to 3.55's or 3.73's as stock. Of course, I now have bigger than stock tires as well (31's - not too much bigger), so I am more seriously considering swapping gears, now that it seems to be a lot taller gearset than most. Any suggestions/recommendations? Even going to 3.55's seems like a big step, unless that tranny has low gears in it, which it sure doesn't seem to. Is there anything worthwhile in between 3.08 and 3.55? I can't tell you the last time I spun the tires... As it is now, I get about 10-12 mpg, and would like to try to keep it as close to that as I can, especially with all the freeway driving I do. I would just like a little more jump off the line, so to speak.
Thanks, everyone!
Chuck
Thanks, everyone!
Chuck
Senior User
Joined: Jun 1999
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does this sound right to you?
With you size tires you might want to go with 3.73 or better. I can tell you that with stock 75R14 tires, the jump between 3.08 and 3.55 is big. Mostly when towing 
if you go to http://www.4lo.com they have a gear/tire calculator to help with your decision.
Good Luck
if you go to http://www.4lo.com they have a gear/tire calculator to help with your decision.
Good Luck
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Joined: Jul 1999
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does this sound right to you?
Chuck ,
If it says 3.08 , thats likely what it is ...My 90 has the same . I guess the engineers try to balance what will deliver all around best general use ? Most people want the mileage vs getting all the engine has to offer . I have 31 10 50 15 tires on my truck and I never use 5th gear unless Im going at least 65 . Im sure going to a 3.55 wont hurt your mileage , plus it will probably give you a little extra boost if you tow anything .
Paul
If it says 3.08 , thats likely what it is ...My 90 has the same . I guess the engineers try to balance what will deliver all around best general use ? Most people want the mileage vs getting all the engine has to offer . I have 31 10 50 15 tires on my truck and I never use 5th gear unless Im going at least 65 . Im sure going to a 3.55 wont hurt your mileage , plus it will probably give you a little extra boost if you tow anything .
Paul
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does this sound right to you?
Thanks for the replies...
I figure I'll probably end up getting 3.55's, since I don't tow worth a damn, and I'm on the freeway entirely too much. Gotta start saving my pennies and recycling aluminum cans...
thanks again,
chuck
I figure I'll probably end up getting 3.55's, since I don't tow worth a damn, and I'm on the freeway entirely too much. Gotta start saving my pennies and recycling aluminum cans...
thanks again,
chuck
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From: Copley, OH
does this sound right to you?
If you really want to split the difference, you could go to 3.27s. With 31" tires they would just get you back to the stock 3.08 gears / 29" tires peformance level. With a 351, I wouldn't be afraid of going all the way to 4.10s with 31" tires, although that would probably hurt your fuel economy. With 3.55s you're likely to see your gas mileage IMPROVE over the 3.08s. 3.08 is just not enough gear for a big heavy truck; your engine is doing all the work instead of the drivetrain helping it out. Go for the 3.55s, you'll like them.
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does this sound right to you?
My 300-6/5spdOD '91 was delivered with a towing package which included 3.55 gears and P235/75-15 tires. The 31X10.50-15 size was an option.
Freeway rpm with the P235 and the 3.55 ratio was 2150 @ 65mph, and overall mileage was in the 15-17 mpg neighborhood.
I subsequently dropped to a 4.10 gear. RPM is 2800 at 70, and mileage is 12. But...it is easier to drive around town and on the trail, plus it made towing a 5,000-lb. RV a whole lot easier.
The 3.55 ring-and-pinion is sitting in the garage, collecting dust, in perfect condition, and waiting for someone to E-Mail me for a can't-miss deal.
Ed (selt@flash.net)
Freeway rpm with the P235 and the 3.55 ratio was 2150 @ 65mph, and overall mileage was in the 15-17 mpg neighborhood.
I subsequently dropped to a 4.10 gear. RPM is 2800 at 70, and mileage is 12. But...it is easier to drive around town and on the trail, plus it made towing a 5,000-lb. RV a whole lot easier.
The 3.55 ring-and-pinion is sitting in the garage, collecting dust, in perfect condition, and waiting for someone to E-Mail me for a can't-miss deal.
Ed (selt@flash.net)
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