Highway speed gear 3.07 vs 2.87

[m37charlie]

Acela quoted me $25k a couple of years ago installed in a FMTV, but I have very good reason to believe one can get the part for <$10k. I know whenever I mention lack of low range in FMTV people ALWAYS retort “torque converter”. But I have 53 years driving 4wds in general and 17 years driving a heavy Unimog “RV”. Nothing, but nothing, can make up for lack of gear reduction.
A 6.14 FMTV has <43:1 reduction available. Torque converter is useless going down steep hills. 43:1 with 46” tires is like a paltry 29:1 with 32s. My first Landcruiser in 1969 with 3 on the tree had 26:1 in low 1st, initially with 29s.
Going slow prevents disasters, protects occupants, protects drivetrains and tires and camper contents.
The 2.87s with the 2 speed transfer and 49” tires is geared 5% faster than 3.07s with 46s.
With stock tires it’s almost identical. Except for an additional 2.266 reduction in low range.
Like I said I’ve never driven a FMTV, let alone one with fast gears.
But in my 27k lb 260hp 700 ft-lb camper, I wouldn’t be a happy camper if working gears (5.76:1) didn’t go below 6th (out of 8 speeds).
I’m sort of surprised none of the (they tend to be high $$$) Acela or even spruced up surplus FMTV builds that I’ve seen have even tried to source a 2 spd TC.

 

[Awesomeness]

that would be light years more expensive process,;seems to me ,compared to 2.87's, combination14.0r20 tire and 3.07 (combo results also in approx same ratio as 2.87) or the new gear reduction removal hubs now being sold.

Obviously, but it would give you the option to disengage it.

 

[m37charlie]

Remove the 2:1 at the hubs? Sure, with just 3.9s and 46s under 1400rpm at 60 mph. If it even would have the power to go that fast. But worthless going uphill, or with 8000 lb load, and especially on any sort of rough slow going.
3.9, 3.14, and 2.87 total gear reduction would all work great if one put 12-14” wide, 30-32” diameter mall cruiser car tires on it.
Don’t people usually buy these kind of vehicles to do heavy work off good roads and/or for go-almost-any RV?
Why would anyone even seriously consider eliminating the 2:1 planetary hub gearing? Although admittedly welding a few planetary gears IS cheap…

 

[DeMilitarized]

Remove the 2:1 at the hubs? Sure, with just 3.9s and 46s under 1400rpm at 60 mph. If it even would have the power to go that fast. But worthless going uphill, or with 8000 lb load, and especially on any sort of rough slow going.
3.9, 3.14, and 2.87 total gear reduction would all work great if one put 12-14” wide, 30-32” diameter mall cruiser car tires on it.
Don’t people usually buy these kind of vehicles to do heavy work off good roads and/or for go-almost-any RV?
Why would anyone even seriously consider eliminating the 2:1 planetary hub gearing? Although admittedly welding a few planetary gears IS cheap…

Look at the eco hub forum. People are having great success with it and are ordering them like crazy.

 

[GeneralDisorder]

Remove the 2:1 at the hubs? Sure, with just 3.9s and 46s under 1400rpm at 60 mph. If it even would have the power to go that fast. But worthless going uphill, or with 8000 lb load, and especially on any sort of rough slow going.
3.9, 3.14, and 2.87 total gear reduction would all work great if one put 12-14” wide, 30-32” diameter mall cruiser car tires on it.
Don’t people usually buy these kind of vehicles to do heavy work off good roads and/or for go-almost-any RV?
Why would anyone even seriously consider eliminating the 2:1 planetary hub gearing? Although admittedly welding a few planetary gears IS cheap…

Ignorance is bliss isn't it?

 

[Awesomeness]

Remove the 2:1 at the hubs? Sure, with just 3.9s and 46s under 1400rpm at 60 mph. If it even would have the power to go that fast. But worthless going uphill, or with 8000 lb load, and especially on any sort of rough slow going.
3.9, 3.14, and 2.87 total gear reduction would all work great if one put 12-14” wide, 30-32” diameter mall cruiser car tires on it.
Don’t people usually buy these kind of vehicles to do heavy work off good roads and/or for go-almost-any RV?
Why would anyone even seriously consider eliminating the 2:1 planetary hub gearing? Although admittedly welding a few planetary gears IS cheap…

They consider it because they don't understand physics.

 

[DeMilitarized]

They consider it because they don't understand physics.

Do your own research before making a blanket statement like that.

 

[Awesomeness]

Do your own research before making a blanket statement like that.

I did, it's called physics. You can't drop the 2:1 in the hubs, and make the truck better at everything (e.g. MPG, speed, pulling, etc.). It's not even worth arguing with stuff so completely ignorant. It's snake oil.

 

[m37charlie]

I guess with 3.9 the transmission would hunt between 5 and 6 a lot.
I will check the site out of curiosity.

 

[DeMilitarized]

I did, it's called physics. You can't drop the 2:1 in the hubs, and make the truck better at everything (e.g. MPG, speed, pulling, etc.). It's not even worth arguing with stuff so completely ignorant. It's snake oil.

The gears in the trans were never designed with a 2:1 in mind which makes them short. You are always either on the bottom end or top end with no power or torque because the engine speeds by that rpm range. With the eco hubs it allows the transmission to do its job and let the torque converter do some reduction as it is supposed to and doesn’t do stock.

 

[Ronmar]

Remove the 2:1 at the hubs? Sure, with just 3.9s and 46s under 1400rpm at 60 mph. If it even would have the power to go that fast. But worthless going uphill, or with 8000 lb load, and especially on any sort of rough slow going.
3.9, 3.14, and 2.87 total gear reduction would all work great if one put 12-14” wide, 30-32” diameter mall cruiser car tires on it.
Don’t people usually buy these kind of vehicles to do heavy work off good roads and/or for go-almost-any RV?
Why would anyone even seriously consider eliminating the 2:1 planetary hub gearing? Although admittedly welding a few planetary gears IS cheap…

Well so far it is testing out pretty well… go checkout the ECO hub discussion…

 

[Awesomeness]

Well so far it is testing out pretty well… go checkout the ECO hub discussion…

I did read it. It just wasn't worth jumping into that circus.

 

[DeMilitarized]

I did read it. It just wasn't worth jumping into that circus.

Buy them and prove everyone is wrong

 

[Awesomeness]

Buy them and prove everyone is wrong

Can't prove a negative.

 

[m37charlie]

So, after reading the Eco Direct post…0.78x3.07x450 rev/mile = 1078 engine rpm at 60 mph in 7th…
It might get rolling decently using 1st all the time.
I think Caterpillar might not approve of running the vehicle up against air resistance max speed at that low rpm might be called lugging, although if allowed to the transmission would find a half decent gear. Maybe 5 or 6 depending on load.
Wouldn’t want to change hubs in the middle of a trip in a dirty environment.
Cheaper? Yes.
People who spend $120-170k on an Acela + many $100ks more on a fancy camper box wouldn’t go for it.
But it’s an interesting idea. It might, maybe, pull 7th with 3.9s empty.
3.04 final gearing. My Mog (similar weight and powerplant and air resistance and tires) has 4.36 final gearing in 8th.

 

[DeMilitarized]

So, after reading the Eco Direct post…0.78x3.07x450 rev/mile = 1078 engine rpm at 60 mph in 7th…
It might get rolling decently using 1st all the time.
I think Caterpillar might not approve of running the vehicle up against air resistance max speed at that low rpm might be called lugging, although if allowed to the transmission would find a half decent gear. Maybe 5 or 6 depending on load.
Wouldn’t want to change hubs in the middle of a trip in a dirty environment.
Cheaper? Yes.
People who spend $120-170k on an Acela + many $100ks more on a fancy camper box wouldn’t go for it.
But it’s an interesting idea. It might, maybe, pull 7th with 3.9s empty.
3.04 final gearing. My Mog (similar weight and power and air resistance and tires) has 4.36 final gearing in 8th.

bro didn’t read it at all. Cruise in6th downhill sometimes 7th

 

[ramdough]

Acela quoted me $25k a couple of years ago installed in a FMTV, but I have very good reason to believe one can get the part for A 6.14 FMTV has Going slow prevents disasters, protects occupants, protects drivetrains and tires and camper contents.
The 2.87s with the 2 speed transfer and 49” tires is geared 5% faster than 3.07s with 46s.
With stock tires it’s almost identical. Except for an additional 2.266 reduction in low range.
Like I said I’ve never driven a FMTV, let alone one with fast gears.
But in my 27k lb 260hp 700 ft-lb camper, I wouldn’t be a happy camper if working gears (5.76:1) didn’t go below 6th (out of 8 speeds).
I’m sort of surprised none of the (they tend to be high $$$) Acela or even spruced up surplus FMTV builds that I’ve seen have even tried to source a 2 spd TC.

Cost aside….. I think the ideal solution would be a two speed transfer case.

I have an old automatic Toyota with a two speed transfer case that I used to off-road. (I know…apples- oranges), but I will will say I was always glad I had the low range when off-road. That is especially true with down hills or when trying to bump up and over a big object. It gives you way better control. Less likely to slam into things and break things. Lower impulses, etc…. A torque converter does not give you that control. I went through some pretty nasty trails. Not as crazy as others though.

There are a couple of things here that are at play:

My truck has an exhaust brake, which I am guessing will probably be a huge benefit (like low range down hill). I am ignorant here, but please help me understand if there is a negative off-road to using exhaust brake.

Everyone has a different understanding of what “off-road” is. To me, if you can’t get at least one tire hanging in the air (and you have to exercise your steering to pick lines), you are just on a dirt road. If you don’t need a spotter, looking at tire placement occasionally, you are on a dirt road.

Most people do not really go off-road by my definition.

When you pack everything in an RV, you probably want to pick easier trails as the loss of the truck or break of parts is more of a risk. Plus, big boxes are fragile…. Don’t want to pop holes in your skin.

99% of my 240K miles on my Toyota were on road.

With all that said, I can really see why people are considering removing the hub reduction or making gear changes. These trucks were meant for being off-road capable with a tow truck or convoy near by. That makes them not the greatest off-road (but very good) and not that efficient on road. The designers dumbed it down and compromised.

I would wager that most everyone that does the hub conversion are really only going on dirt roads…. Especially with their expensive habitat boxes. But, dirt roads, beaches, deep snow, poorly maintained roads, are places a normal RV can’t go. So, they are getting a very capable RV in comparison to a Winnebago. I have considered and am still toying with the idea of hubs. Most places I want to go are wide open places like I mentioned above. I don’t want to risk my truck. A tow behind jeep, I could see abusing.

With all that said, I think 99% of the people considering the hub change probably would benefit from the better street performance. And probably most would not take these trucks where working gears would matter.

I am still asking myself, after all of my time and money on a habitat, would I really need the off-road a capability these trucks have. I probably would enjoy the fuel economy better. But then again, if I needed the lower gears, I would be kicking myself for not having them. Wish the army put in a two speed transfer case to make this argument all mute.


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[ckouba]

I would wager that most everyone that does the hub conversion are really only going on dirt roads…. Especially with their expensive habitat boxes. But, dirt roads, beaches, deep snow, poorly maintained roads, are places a normal RV can’t go. So, they are getting a very capable RV in comparison to a Winnebago...

...I think 99% of the people considering the hub change probably would benefit from the better street performance. And probably most would not take these trucks where working gears would matter.

I am still asking myself, after all of my time and money on a habitat, would I really need the off-road a capability these trucks have. I probably would enjoy the fuel economy better.

^ = me

 

[GeneralDisorder]

I did, it's called physics. You can't drop the 2:1 in the hubs, and make the truck better at everything (e.g. MPG, speed, pulling, etc.). It's not even worth arguing with stuff so completely ignorant. It's snake oil.

There's always trade offs. No one said the truck would be "better" at pulling - or I missed it. Do you have that quote handy?

MPG and speed is improved. Period. There's absolutely no argument you can present against this. I clocked over 10 MPG and I have personally done 85 mph.

What are you doing with your truck that you believe it will be compromised for the task without the reductions?

If you find yourself in the PNW with your truck I would love to setup a drag race event!

 

[Ronmar]

I did, it's called physics. You can't drop the 2:1 in the hubs, and make the truck better at everything (e.g. MPG, speed, pulling, etc.). It's not even worth arguing with stuff so completely ignorant. It's snake oil.

Your not really dropping the 2:1, you are shifting it to the torque converter, which is so lightly used in these trucks typically because of the 2:1 in the hubs. IMO, Thats why the 2-3 shift happens so fast and so harsh(The lockup clutch was programmed to expect more load and slippage). With shifting the load into the TC, normal driving should be improved. Yes, you may not be able to muscle your way over an 18” curb anymore, but you also wont be roaring at max governed with high speed, high angle driveshafts anymore to try and flow with traffic….