3.73 or 4.10?
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Cross-Country
Joined: Jul 2014
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3.73 or 4.10?
Hey Y'all, looking for some input as I'm not too savvy with gear ratios.
I have a 94 f150 that currently has a 351w with rv cam to increase towing capabilities backed with a M5OD and 3.55s in the rear end. At the moment doing 100km(60mph) I'm reving out at about 3200rpm this is not helpful in fuel economy or a happy engine.
I want to use the truck to tow horses (lightweight trailer and 2 horses) as a daily and hunting/back country camping truck.
currently running 33s will probably bump up to 35s when I need new tires. i will be swaping it to a ZF5-47 in the future.
So what I'm trying to figure out with all this is would 3.73s or 4.10s would be better for what im doing.
any help or insights would be greatly appreciated.
I have a 94 f150 that currently has a 351w with rv cam to increase towing capabilities backed with a M5OD and 3.55s in the rear end. At the moment doing 100km(60mph) I'm reving out at about 3200rpm this is not helpful in fuel economy or a happy engine.
I want to use the truck to tow horses (lightweight trailer and 2 horses) as a daily and hunting/back country camping truck.
currently running 33s will probably bump up to 35s when I need new tires. i will be swaping it to a ZF5-47 in the future.
So what I'm trying to figure out with all this is would 3.73s or 4.10s would be better for what im doing.
any help or insights would be greatly appreciated.
Logistics Pro
Joined: Nov 2013
Posts: 3,928
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From: Mojave, Ca
Is that 3200rpm in 4th gear or 5th gear? If your towing with stock tires, you'll want 4.10. if you want to get 33 or 35" tires, look at 4.56 or 4.88 gears. Your towing capacity and mileage will go down when the tire size goes up. These trucks work really well with stock size tires. If you want the truck to haul and tow, stick with stock tires.
Hotshot
Joined: Nov 2017
Posts: 17,484
Likes: 2,773
From: Northern Ontario
3200 RPM doesn't make sense.. even in 3rd.
Use this to play with your number/combination/tire sizes...
Gear Ratio Calculator
Use this to play with your number/combination/tire sizes...
Gear Ratio Calculator
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
3200rpm is 90mph in 4th gear, 120mph in OD with your powertrain combo. Did you make a typo and meant 2200rpm? That would make a lot more sense.
Has the speedo been corrected for those tires? Something isn't right here.
Has the speedo been corrected for those tires? Something isn't right here.
Logistics Pro
Joined: Aug 2010
Posts: 3,716
Likes: 583
From: Chillicothe
Is the tachometer you are usimg the factory dash tach for the 300? I wonder if the 6 cylinder tach is reading the 8 cylinder signal wrong and giving a false reading. That or the tach is just malfunctioning. Because as stated before. There is no way with the gears you say you have that the speedometer and tach are both correct.
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Cross-Country
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Factory dashbwith the 351 ecu.
factoring the sound difference between the trucks and how it screams now tach may be out 1 or 200rpm
factoring the sound difference between the trucks and how it screams now tach may be out 1 or 200rpm
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Hotshot
Joined: Sep 2001
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Is the PSOM reprogrammed for the current tire size? Is the speedometer accurate?
With 3.55 and 5th gear OD the RPM would be nowhere close to 3000. I'm thinking the tach is reading higher than actual. I know the clusters are year specific and not interchangeable for all years, but never heard of having to have a tach cluster specifically for I6 or V8. Kinda seems like that is what is going on here though unless someone has already swapped the gears out.
I'd skip the 35s and stick with the 33s for a half ton that tows and that has the M5OD.
Would also go with at least 4.10 or lower for the larger tire size. Since it is a 5.8 it does have more low end grunt than a 5.0. With a 5.0 I'd say 4.56.
With 3.55 and 5th gear OD the RPM would be nowhere close to 3000. I'm thinking the tach is reading higher than actual. I know the clusters are year specific and not interchangeable for all years, but never heard of having to have a tach cluster specifically for I6 or V8. Kinda seems like that is what is going on here though unless someone has already swapped the gears out.
I'd skip the 35s and stick with the 33s for a half ton that tows and that has the M5OD.
Would also go with at least 4.10 or lower for the larger tire size. Since it is a 5.8 it does have more low end grunt than a 5.0. With a 5.0 I'd say 4.56.
Logistics Pro
Joined: Aug 2010
Posts: 3,716
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From: Chillicothe
I ran the Vin in your picture. It comes back as 3.08 gears and 4x4.... which the door tag shows 3.55s so that is contradictory. Is the truck in low range and you don't realize it? I mean I think 3200 in 5th and low is like 55 or something.
Hotshot
Joined: Nov 2017
Posts: 17,484
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From: Northern Ontario
Either your tach is wrong, tire size is wrong, stuck in low range, speedometer is way off, or you have different gearing than posted.
Does it sound like it is running at 3200 rpm?
According to my calculator, 3200 rpm @ 60 mph you need to be running:
6.63:1 with a final / OD gear of 0.79 or 6.55:1 with 0.80. True 33” tires.
Do you know the history of the truck, or verified personally what gearing you have?
Does it sound like it is running at 3200 rpm?
According to my calculator, 3200 rpm @ 60 mph you need to be running:
6.63:1 with a final / OD gear of 0.79 or 6.55:1 with 0.80. True 33” tires.
Do you know the history of the truck, or verified personally what gearing you have?
Thread Starter
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Cross-Country
Joined: Jul 2014
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JJF20
BFG K02 33s
Definitely sounds like it's hitting those high rpms, drastically different sound from 2200 rpm in the last truck this engine was in
spun the tires on Jack's last night 3 and a half rotations of the driveshaft.
BFG K02 33s
Definitely sounds like it's hitting those high rpms, drastically different sound from 2200 rpm in the last truck this engine was in
spun the tires on Jack's last night 3 and a half rotations of the driveshaft.