5.4 with 37's?

[depark]

Hi everyone,
I’m hoping to get some opinions on whether to run 35’s or 37’s with a 5.4. The main question I have is does the 5.4 have enough power to run 37’s with 4.88 gears and still be able to tell up to 6000 lbs.? Just for reference I calculated the difference in rpm for the stock, 4.56 and 4.88 values. All of these are at 65 mph without O/D.

3.73 – 2771 rpm – 29.4” tires
4.56 – 2837 rpm – 35.1” tires – 1.5 mph lower speed reading
4.88 – 2881 rpm – 37.0” tires – 2.5 mph lower speed reading

The way I interpret the numbers is that it can run 37’s and still tow well because of the slightly higher rpm. My reasoning may be flawed, any advice would be appreciated. I do understand that 35’s and the 5.4 are well matched and many have chosen that option. Still are 37’s a possibility?
Thanks
Darryl

 

[depark]

It's for a 2013 E350 with a 5.4. It will have a 6" lift and 3" body lift. Towing 6000 lbs. in mountains of BC where I live is the biggest concern. Just trying to figure out which direction to go before I pull the trigger.
Cheers
Darryl

 

[Burlydirtyhippy]

Just an opinion,.. 4.88s and 35s. Not just gear ratios but a lot more rolling mass to consider.

 

[ujoint]

I had a 2011 5.4 on 35s with 4.88s, great for DD use. I did tow a few times with it, 5-6k and it got the job done but I wouldn't want to do it often. I'd be concerned with the 4R75 towing that much weight often.

 

[depark]

I had a 2011 5.4 on 35s with 4.88s, great for DD use. I did tow a few times with it, 5-6k and it got the job done but I wouldn't want to do it often. I'd be concerned with the 4R75 towing that much weight often.

What kind of fuel mileage did you get with V5? How was it at 75-85 mph (not towing of course)?
Thanks
Darryl

 

[Len.Barron]

Just an opinion,.. 4.88s and 35s. Not just gear ratios but a lot more rolling mass to consider.

I agree...You're going to be pushing 14,000lbs GCVW and your wind profile will be that of a concrete block. 5.4's don't mind rev'ing so take advantage of that. Get used to driving a little slower.

 

[Mickey Bitsko]

What transmission do you have?
Ford offered a 5.4 in the f350.

 

[ujoint]

What kind of fuel mileage did you get with V5? How was it at 75-85 mph (not towing of course)?
Thanks
Darryl

I don't check MPGs frequently in any of my rigs. V5 saw ~12MPGs when I did.

 

[derjack]

Hi everyone,
I’m hoping to get some opinions on whether to run 35’s or 37’s with a 5.4. The main question I have is does the 5.4 have enough power to run 37’s with 4.88 gears and still be able to tell up to 6000 lbs.? Just for reference I calculated the difference in rpm for the stock, 4.56 and 4.88 values. All of these are at 65 mph without O/D.

3.73 – 2771 rpm – 29.4” tires
4.56 – 2837 rpm – 35.1” tires – 1.5 mph lower speed reading
4.88 – 2881 rpm – 37.0” tires – 2.5 mph lower speed reading

The way I interpret the numbers is that it can run 37’s and still tow well because of the slightly higher rpm. My reasoning may be flawed, any advice would be appreciated. I do understand that 35’s and the 5.4 are well matched and many have chosen that option. Still are 37’s a possibility?
Thanks
Darryl

If you want to know it, you can calculate that. Just go further and answer that question yourself:
As usual I would suggest this webside, but you can of course search all gearing by yourself > http://www.grimmjeeper.com/gears.html

Now you know engine speed at any given km/h. The other way around and every other thing as well.
You want to know if the given 5.4 (I think you meant the engine) has enough power? Nobody can tell you what enough is for you. But you can calculate the gearing of your diff to have exact the same power at the wheels as stock or better.
This is just final gearing at the wheels times torque at given RPM. Simple as that. Check out this video: [video]https://youtu.be/zZBqb0ZJSwU[/video] This is what drives your truck - no number at flywheel, at torque at the moon ...

In 2 minutes you get the gearing that will have the same "power" as stock. Don´t know if this is enough or not. But you can easily calculate that as well. Add 3000 tons and e.g. 5% slope.


In general: The lower the gearing (high #) the more power has your truck, you buy this with a lower mpg and louder sound. An Unimog is only good because of that. A MAN KAT 1 gets up to 80 km/h with its 16.00 at maximum engine speed! [50mph and ~50" wheels] Weather it has a 12 cylinder Deutz engine with plenty of power.


PS: I really don´t know why this is asked every week! There was just the same post a week ago, just with different tires. Does nobody anymore use the :Astrologist:?????????????????????????

 

[cjken]

I would stick to 35’s with the 5.4. I had 33’s on my 5.4 and have run both 37’s and 35’s on my 7.3.

I can’t think of a reason you would need to run 37’s other than the look awesome!
35’s should do everything you need and be a bit more practical. Even though you can get the rpm in line with stock, you are rotating a lot more mass at a greater radius with 37’s. The increased moment of inertia is not insignificant.

 

[Raul]

I would stick to 35's with the 5.4. I had 33's on my 5.4 and have run both 37's and 35's on my 7.3.

I can't think of a reason you would need to run 37's other than the look awesome!
35's should do everything you need and be a bit more practical. Even though you can get the rpm in line with stock, you are rotating a lot more mass at a greater radius with 37's. The increased moment of inertia is not insignificant.

Amen. I agree completely with the above. The extra ROTATING mass will affect your acceleration (OK, you can live with that) but also your deceleration. Your brakes not only take care of slowing the whole mass of your vehicle, but also the rotation of the wheels themselves. Axle fatigue is another issue. Changing gear ratios will make that the torque requirements to your engine remain the same, but the torque that the shaft has to transfer to your wheels will be increased..... 37" look awesome though.

 

[Corneilius]

I agree with the last couple posts. ESPECIALLY considering you're running a dana44. I think it falls into the category "just because you can, doesn't mean you should"

 

[malcolmzilla]

I have found that for towing, even with my 6.7 Dodge, that the reciprocating mass is a big consideration. I can run 37's on it unloaded, but when I hitch up the braking and acceleration are greatly affected, much better with a smaller tire which I will swap to for extended towing. Why not have 2 sets of tires, drop down to 33's to tow?

 

[Chili]

The previous posts are essentially in agreement with the matter of rolling weight and the extra strain on your vehicles systems. One way to look at it is to weigh the factory wheel and tire combination and then calculate the difference of your new wheel and tire combination. You might get heavier/larger tires, but if you reduce the weight of the wheels by buying a lighter alloy wheel, you might mitigate the increased effect of the torque. That's what I did on my truck. The alloys and larger tires only weigh about 15 lbs. more than the factory combination, so I didn't need to worry about ill effects. just my .02.

Speaking purely theoretically, but wouldn't the impact of the overall tire and wheel weight, especially as it relates to the inertia of the rotating mass, change drastically depending on how far out from the center the weight is? Thinking about that experiment where you spin on a chair in a circle. If you extend your arms and legs out while spinning, you will slow down. If you pull them in, you will speed up. The same weight is in the chair..

So in the example of your tires / wheels, if you increase tire weight while decreasing wheel weight, you may be keeping the overall weight the same, but the forces created while spinning will still be very different because of where that weight is. The further out the weight resides the more power it will take to get them spinning and they will be harder to stop once moving.

No real point here, other than the fact that when we're talking about physics you really have to consider all variables.

 

[winmag4582001]

Speaking purely theoretically, but wouldn't the impact of the overall tire and wheel weight, especially as it relates to the inertia of the rotating mass, change drastically depending on how far out from the center the weight is? Thinking about that experiment where you spin on a chair in a circle. If you extend your arms and legs out while spinning, you will slow down. If you pull them in, you will speed up. The same weight is in the chair..

So in the example of your tires / wheels, if you increase tire weight while decreasing wheel weight, you may be keeping the overall weight the same, but the forces created while spinning will still be very different because of where that weight is. The further out the weight resides the more power it will take to get them spinning and they will be harder to stop once moving.

No real point here, other than the fact that when we're talking about physics you really have to consider all variables.

^^^You just made my brain hurt.


Just changed my gears today from 3.73 to 4.30

245/75 R16 30" @ 70mph 2080rpm 3.73
285/75 R16 32.5" @ 70mph 1940rpm 3.73
285/75 R16 32.5" @ 70mph 2270rpm 4.30