Regear your Earth Roamer, Global X, Tiger, etc. Now stocking gears for F450 / F550

nitro-gear

Supporting Sponsor - Differential & Axle Parts
We are now stocking Several different gear ratios to suit Ford F450 / F550 Vehicles including Earth Roamers, Global Expedition Vehicles, Tiger, etc. If you are running larger than stock tires, your performance will suffer due to improper gearing. This becomes especially important on trucks that have been outfitted with the Continental MPT81 41" tire setup. We've actually fitted 5.38 gear ratio to our 2004 F450 4x4 RV. It is running 42" (11r22.5) Tires and the 6.0L powerstroke (modified for reliability:)). The truck weighs about 15,000 lbs and has no troubles pulling a near 10k trailer. It also stays in overdrive on most grades as it should. Fuel economy on average (lots of mountain driving, not towing) is about 11-12 mpg.

Contact us for more info. This is a very worthwhile modification for your Overland Adventure vehicle. We also offer Lockers and limited Slip Differentials, Replacement parts, and much more.

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More info here:
https://www.facebook.com/media/set/?set=a.508089502563145.105666.178075115564587&type=3

http://www.expeditionportal.com/for...ome-on-42-s-Build-Thread?highlight=nitro+f450
 

camperman

Observer
Nice one! But this will increase RPM required to obtain let's say, 60MPH. Is it making any improvements in fuel mileage over stock gearing? (Both on 41" tires?)
 

haven

Expedition Leader
When you swap the F450's standard rims and tires for the 22.5 inch rim and larger tires, the larger circumference and extra weight of the oversize tires bogs the engine down, often to the point where you have to shift down to a lower gear. The new gearing in the diffs will compensate for the taller tire. The result should be RPM at any given speed that's closer to that of the stock F450 with its 19.5 inch rims. Fuel economy is improved to the extend that you don't have to shift down. Like Nitro-Gear says, now they're able to run up hills in overdrive.
 

DiploStrat

Expedition Leader
A million years ago I had a Chevrolet Blazer with the factory 350 cubic inch engine and 3.07 gears to spin H78x15 tires. This with a 3+1 manual gear box. I went to 11x15 tires and while the ride and off road abilities increased, there was a tremendous hole in the shift pattern, especially climbing in the Andes above 10,000 feet. The next truck was a Blazer with a 400 cubic inch engine, the same 3.07 gears and factory 10.00x15 tires. With a three speed automatic, things were fine. I changed to 12.00x15 and, with the automatic, there was no terrible hole in the shift pattern, but it was clear that 3.5 gears would have been nicer.

Add a diesel engine to a modern six speed auto transmission and you may not have a problem, but I will be watching with my Tiger and am delighted to see companies offering alternate gear ratios. Especially if they can install them and set them up properly.
 

nitro-gear

Supporting Sponsor - Differential & Axle Parts
I will be watching with my Tiger and am delighted to see companies offering alternate gear ratios. Especially if they can install them and set them up properly.

Unfortunately we are on the other side of the country from you! If you decide to regear and need to find a company near you let us know. We have many dealers and shops around the country that work with us.
 

DiploStrat

Expedition Leader
Tigers are made to roam. Frankly, given the tight wheel wells on a Chevrolet, the next evolution would be a 4" lift, new wheels, tires, etc. and the need for such modifications is most likely to be proven in the west. (Or at the beach, but I am too old to be a beach bunny and tides scare me.)

But, should I end up with 35.00x12x18 tires, it is good to know that there are gearing options. Given the weight of a Tiger, a front locking diff might come before different ratios. Just need to see how much rough road this beast actually sees.
 

turbopilot

Observer
FYI, EarthRoamers, at least since 2008, have been provisioned with 4.88 Ratio Limited Slip Axles straight from Ford. Don't know about earlier years. Most EarthRoamer owners find that gear ratio about perfect for the MPT81's.
 

nitro-gear

Supporting Sponsor - Differential & Axle Parts
Well Yes, the 4.88 is more tolerable with the MPT81 on the late model 6.7L trucks. That said, I'm not so sure there are any Earth Roamer owners that Have changed their gear ratio to 5.13 or 5.38, so its hard to say otherwise if one has not experienced it. Remember the F550 comes with 4.88 with about a 31.5" tire. Stepping up to a 41" tire gives a significant reduction in RPM's, and below the intended / ideal operating range. Considering that 4.88 is on the low side for 31's, it is tolerable for some, but I wouldn't say perfect. Models with the 6.0L or 6.4L really need it. The 6.7L seems to be more tolerant with a bit taller gearing, but I dont think anyone is saving fuel with the 4.88/mpt81 combo, and certainly suffering a compromise in performance.

Some examples
Late F550, 4.88, 225/70r19.5" (31.5") tires 2150 @ 60 MPH
Late F550, 4.88, 335/80r20 (41") tires 1680 @ 60 MPH

Late F550, 5.38, 335/80r20 (41") tires 1850 @ 60 MPH


As you can see, even with 5.38 the over all gearing is still higher than stock (lower rpm). Based on the extra cost of wear & tear of other drivetrain components (transmission), fuel economy, And overall lack of performance, it really makes sense to gear appropriately. It becomes even more essential on a 15k+ lb vehicle.







FYI, EarthRoamers, at least since 2008, have been provisioned with 4.88 Ratio Limited Slip Axles straight from Ford. Don't know about earlier years. Most EarthRoamer owners find that gear ratio about perfect for the MPT81's.
 

camperman

Observer
Yes, that makes sense. First I thought if RPM's higher, fuel consumption will be higher. But I forgot about ideal operating speed. If truck is on 37" 5.38 gearing is suffiecent for highway&offroad use?
 

turbopilot

Observer
The 6.7L seems to be more tolerant with a bit taller gearing, but I dont think anyone is saving fuel with the 4.88/mpt81 combo, and certainly suffering a compromise in performance.

My only experience is driving a 6.7L/MPT81 EarthRoamer. After 34,000 miles I pretty well understand this setup. Running the ER @ 60 mph, flat terrain, sea level and no wind my 17,000 lb my fully load ER LT will typically get around 12.5 mpg. The biggest variable in fuel efficiency is wind. In the ER a 30 mph head wind can bring the fuel efficiency down by 2 mpg. Altitude and temperature are the other big variables. High and cool, the 6.7L tends to regenerate the DPF passively, low and hot the active regeneration frequency increases significantly knocking down fuel economy.

Are there graphs that predict the fuel efficiency versus RPM for the 6.7L engine?
 

rblackwell

Adventurer
The thing that has always worried me about my ER is tire availability. We have a 2008 with the 295/60R22.5. With these tires the truck feels under geared (that is too many RPMs).
Talking to other owners the 335/80R20s seem to make the gearing better.
The problem is that for world travel neither the 295/60R22.5's nor the 335/80R20s are a good choice of tire - just not available (they are about as available as the 395/85R20's on my current Mog - that is not at all).

The most commonly available tires in both South America and Central Asia (based on my own imperfect survey) are:
11R20, 12R20
11R22.5
295/80R22.5 (also 315/65R22.5 385/65R22.5 - but these are too big for an ER -- I think)

For someone seeking to travel the world 11R20 or 11R22.5 seem like a good choice. My rough calcs suggest that for these tires (which I think are a little bigger than the MP81's) a re-gear would be a good idea (not to mention lockers front and rear).
To put these 11's on the ER I think would require an increase in the suspension lift as I don't see them having enough clearance on the rear as the rear of the ER camper cannot be trimmed. The fresh water tank sits in front of the rear wheels on one side and the house batteries on the other.

So I commend you for making more gears available for the F550, I like the look of your truck with the 11's. If I ever prepared our ER for travel outside of North America I would come looking for how to put 11's on.
 
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When I was in Australia I thought I was going to have to replace my 395s in order to do the Asia portion of my trip (I didn't because my wife came down with ALS). I carried one mounted spare on the back plus 2 unmounted on the roof. I did eventually find some brand new 395 XZLs in Perth, for a pretty penny of course.
The point of this of course is that with 3 spare tires I could have made it another ~30000 mi by using up my used tires in sequence on the one un-replaced position. They had about 8 to 10/32" when I replaced them with my new or almost new spares.
Any conceivable combination of tire disasters could be handled by 3 spares, and the unmounted ones are significantly lighter than mounted ones.
So I will stay with 395s.

Charlie
 

nitro-gear

Supporting Sponsor - Differential & Axle Parts
The 11r22.5" are 42" tall, but pretty skinny. All I have is 2" lift and it does have the 05+ Axle. So essentially setup similarly fitment wise to an ER. The rear on mine appears to have even less clearance than the ER's from what I've seen. They work pretty well, but really like aired up to over 100 psi. Fortunately the tread is deep and cushions well. I would like to be able to air down a bit more for dirt roads etc.


The thing that has always worried me about my ER is tire availability. We have a 2008 with the 295/60R22.5. With these tires the truck feels under geared (that is too many RPMs).
Talking to other owners the 335/80R20s seem to make the gearing better.
The problem is that for world travel neither the 295/60R22.5's nor the 335/80R20s are a good choice of tire - just not available (they are about as available as the 395/85R20's on my current Mog - that is not at all).

The most commonly available tires in both South America and Central Asia (based on my own imperfect survey) are:
11R20, 12R20
11R22.5
295/80R22.5 (also 315/65R22.5 385/65R22.5 - but these are too big for an ER -- I think)

For someone seeking to travel the world 11R20 or 11R22.5 seem like a good choice. My rough calcs suggest that for these tires (which I think are a little bigger than the MP81's) a re-gear would be a good idea (not to mention lockers front and rear).
To put these 11's on the ER I think would require an increase in the suspension lift as I don't see them having enough clearance on the rear as the rear of the ER camper cannot be trimmed. The fresh water tank sits in front of the rear wheels on one side and the house batteries on the other.

So I commend you for making more gears available for the F550, I like the look of your truck with the 11's. If I ever prepared our ER for travel outside of North America I would come looking for how to put 11's on.
 

rblackwell

Adventurer
When I was in Australia I thought I was going to have to replace my 395s in order to do the Asia portion of my trip (I didn't because my wife came down with ALS). I carried one mounted spare on the back plus 2 unmounted on the roof. I did eventually find some brand new 395 XZLs in Perth, for a pretty penny of course.
The point of this of course is that with 3 spare tires I could have made it another ~30000 mi by using up my used tires in sequence on the one un-replaced position. They had about 8 to 10/32" when I replaced them with my new or almost new spares.
Any conceivable combination of tire disasters could be handled by 3 spares, and the unmounted ones are significantly lighter than mounted ones.
So I will stay with 395s.

Charlie

Charlie
The comments about 11xR20/11R22.5 apply only to my EarthRoamer.
With our U500 I made the decision(mistake?) to come to Asia with only 1 spare. So far that has not been an issue - no tire problems. In fact I have been
very impressed by the abuse the XZL have taken.
I find it interesting that MB has put 14R20's on the Zetro trucks because 14R20 tires are available in Russia/Mongolia/Central Asia - as they are one of the standard
sizes on Kamaz trucks (the other size on their 6x6 is 425/85R21 - not very useful to me).
The other concern I have been carrying on our current trip are the Hutchison wheels I am using. In the US these felt like a great upgrade over the standard 2 piece steel wheels that were on the U500. BUT - they are sometimes very difficult to split - even while in the US I had trouble separating the two halves - had to inflate the tires to break to two halves apart; dont know what I would do if the tire was ripped and would not inflate. The rubber O-rings are special sizes and need to be replaced EVERY time the wheel is split. And as our other U500 friends have discovered the valves do not like ceramic balance beads.
Once in Europe I may ask an MB dealer about 14R20s
 
One could certainly put 14.00R20 on 10.00-20 rims, at a loss of 6.5% of rear wheel torque. They would "probably" clear the body, since 455/70R24s are almost as tall and significantly wider and that is a tire option on the U500. Not sure about the camper in the rear though.
I hope you didn't combine ceramic beads with CTIS!!!
My slightly used military takeoffs are doing well after 7000 miles but the fronts were out of balance. Surprisingly they got "beaten into balance" on a trip up the Dalton Highway (Haul Road).

Charlie
 

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