You'll be much better off changing to 4.10's. And you'll spend less converting the gear set than rebuilding the transmission.
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Advice Requested
This is a repeat of this topic. I got very few responses last time and while what I got was helpful it didnt really address my question.
My 96 F250 has an auto trans and 3.55 rear end. I would prefer a 3.73 or 4.10 because I tow a 33' fiver from time to time but changing rear ends is complicated by the fact its a 4X4. My solution to date has been to always tow in 3rd (thats Fords recommendation also).
The problem is that with the tranny - rear end - stock 235 80 16 tires I run right at 2500 RPM at 65MPH. Thats on the wrong side of the torque curve and right at the peak for HP. By changing to 295 75 16 tires I will reduce my RPM at 65 MPH to a little over 2300. Not perfect but better position on the torque and power curves.
I have been told by friends in the tire business that the 295s will fit.
I would appreciate your thoughts on this subject.
My 96 F250 has an auto trans and 3.55 rear end. I would prefer a 3.73 or 4.10 because I tow a 33' fiver from time to time but changing rear ends is complicated by the fact its a 4X4. My solution to date has been to always tow in 3rd (thats Fords recommendation also).
The problem is that with the tranny - rear end - stock 235 80 16 tires I run right at 2500 RPM at 65MPH. Thats on the wrong side of the torque curve and right at the peak for HP. By changing to 295 75 16 tires I will reduce my RPM at 65 MPH to a little over 2300. Not perfect but better position on the torque and power curves.
I have been told by friends in the tire business that the 295s will fit.
I would appreciate your thoughts on this subject.
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I have a friend that runs 285x75's on his 97....and it is close. He says they don't rub, but they really fill his wheelwells. Have you considered a taller tire that isn't any wider than the stockers? Something like a 255x85x16 would only be about .4" shorter than the 295x75, but would be 1.7" narrower. Yo9u culd also keep the "E" load rating acceptable tire width for the stock rims.
JMHO.
JMHO.
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From: Derby, Kansas
My reading of your problem is this, you have a 30.4 dia tire and you are wanting to change to a 33.4" dia. Your rear axle ratio is 3.55 to 1 if you add size to 33.4 your axle ratio will be somewhere in the neighborhood of 3.22 to 1. This could be a real loss in towing capability, I don't think I would do it.
If you have problems towing you will have more with this change.
TMHO
fknipfer1
If you have problems towing you will have more with this change.
TMHO
fknipfer1
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88, I am a little confused, in the first part you say you really want 3.73s or 4.10s, then you say with your current ratio you are turning to many rpm at speed. If you want to lower cruise rpm then yes a taller tire will help. If you want 3.73s or 4.10s for towing then your cruise rpm will be higher then it is now. I think the real solution for your problems would be a Gear Vendors or US Gear under/overdrive unit. It would allow you to split gears when accelerating to improve towing performance, and also give you a higher ( numerically lower ) overdrive for better cruising performance.
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From: Everson,WA.
I run 285/75R16. They fit but I had to put bumper extensions on and a 1 1/2'' leveling kit on the front end. It's a 94-97 body style. At 70 I run about 2400 rpm. Oh, I forgot to add I have 4:10 gears with a 5speed stick. I average 19 mpg.
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Originally Posted by psdpower
88, I am a little confused, in the first part you say you really want 3.73s or 4.10s, then you say with your current ratio you are turning to many rpm at speed. If you want to lower cruise rpm then yes a taller tire will help. If you want 3.73s or 4.10s for towing then your cruise rpm will be higher then it is now. I think the real solution for your problems would be a Gear Vendors or US Gear under/overdrive unit. It would allow you to split gears when accelerating to improve towing performance, and also give you a higher ( numerically lower ) overdrive for better cruising performance.
Originally Posted by cookie88
I have a friend that runs 285x75's on his 97....and it is close. He says they don't rub, but they really fill his wheelwells. Have you considered a taller tire that isn't any wider than the stockers? Something like a 255x85x16 would only be about .4" shorter than the 295x75, but would be 1.7" narrower. Yo9u culd also keep the "E" load rating acceptable tire width for the stock rims.
JMHO.
JMHO.
Last edited by Phydeaux88; Oct 7, 2004 at 10:37 PM.
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Ok did some checking.
Replace existing differentials with used from wrecked F-350 $1400 plus labor
leaves me with Dana 60 for front end better than the existing Dana 50
Replace ring and pinion only $1000 plus labor
parts quote from Ford Stealership may be able to get them a little cheaper some where else
I end up keeping the Dana 50
Install aftermarket overdrive Gear Vendors unit $2600 plus $600 install
In 3rd Over gear ratio is .78 instead of .7 which gives about 2000 RPM at 65 MPH
Thats exactly where I want to be HMMMMM but it is Pricey
Replace existing differentials with used from wrecked F-350 $1400 plus labor
leaves me with Dana 60 for front end better than the existing Dana 50
Replace ring and pinion only $1000 plus labor
parts quote from Ford Stealership may be able to get them a little cheaper some where else
I end up keeping the Dana 50
Install aftermarket overdrive Gear Vendors unit $2600 plus $600 install
In 3rd Over gear ratio is .78 instead of .7 which gives about 2000 RPM at 65 MPH
Thats exactly where I want to be HMMMMM but it is Pricey
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Originally Posted by Phydeaux88
In 3rd Over gear ratio is .78 instead of .7 which gives about 2000 RPM at 65 MPH
Thats exactly where I want to be HMMMMM but it is Pricey
Thats exactly where I want to be HMMMMM but it is Pricey
That is where most of us with 4.10's are in od. Mine is at 2000 at 63 mph. If you're satisfied with the unloaded mileage, my suggestion is to tow in 3rd and you save a bunch of cash.
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From: South Texas Coast
Originally Posted by Matthew Groves
Or, you can swap for my 4.10s. You'll get better towing, I'll get the 3.55s
Sounds like a perfect plan. Ever been to Nebraska?
Matthew
Sounds like a perfect plan. Ever been to Nebraska?
Matthew
As far as the swap idea that would work if we both have same diffs but I dont believe we do. You have the new body style and I have the old. I think they went to different front end when they changed
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From: Springfield, MO
I have a 97, so it's the same body style as yours. The best part, is that we would change out both front and rear gears, so we'd still have our 4x4 use! The only bad news is that after the swap, both of us would still have Dana 50s instead of the 60s we crave.
Matthew
Matthew