Hub Removal/Replace

[coachgeo]

I did search first. If I missed a good thread on topic in my search feel free to just hit me over the head and hint at a link or better search terms. (I used google adv. search)

Anyway..... am going to end up with two sets of hubs. One on the truck is for basically Road Racing via a Hub Reduction Elimination you could say. (more on that later) and the other set is Stock.

Can one just pull each complete hub and swap it with the other without major special equipment and/or without disassembling each hub piece by piece in order to remove it completely and do reverse for hub replacing it? Am going to guess complete disassembly/reassembly is required... but one could always hope.

 

[mkcoen]

I guess my simple question would be WHY?

 

[coachgeo]

I guess my simple question would be WHY?

• set A hubs- (modified-3.9 total axle ratio) are great for Interstate highway cruising especially if going on a trip across half the country for example, BUT would suck for off road.
• Set B hubs- (stock 7.8 total axle ratio) are pretty good offroad, but Suck for interstate Highway travel. Granted these would be sorta OK for two-lane highway / taking your time and smell the roses traveling, but this is not a luxury one gets often these days.
• The fact I've end up with both out of the gate.

So for example If I was to say... go to Moab from OH with the Highway set installed then swap Hubs to the other set for few days on the trails..... then swap back again before trip home, life would be

 

[mkcoen]

Leave the stock hubs and stick to insterstates most of the way to Moab. I would recommend several flashing yellow lights and a big sign that says "slow moving vehicle." Better that someone gets stuck behind you on a 4 lane for a couple of minutes vs several miles or more on a 2 lane.

Do you really want to go to the trouble of swapping gear sets in the middle of no where? Ever been to Moab? It is by definition "the middle of no where." What happens when something goes wrong and now you're stuck in the desert waiting for a tow truck big enough (coming out of Provo or Grand Junction, CO) and what that's going to cost you? KISS - keep it simple Sunshine!

 

[coachgeo]

Your point has validity, but so do the reasons folk swap the third member when they figure they will be on highways a lot. If I had a third members to replace what I got I'd consider it. But I dont.. yet I DO have both set of hubs so why not explore that option. Besides instead of forking out more funds for buying a set of different ratio third members I could instead pay for a **** of a lot of fuel and enjoy.

Yes been to Moab. Published an article on it long ago even. But that was only a simplified ruff example. There is driving also west to CA, OR, back south to NV and over into AZ thus getting better mpg on such an Expedition excursions begins to come into play on total costs.... all while still having ability to spend a days/a week off road in between Highway travel is appealing.

Anyway..... its just an exploratory option.

 

[98G]

I haven't done it.

That being said, it's almost certainly more work than you want to regularly undertake, and certainly more than you want to do at a trailhead or on the side of the road.

 

[scottmandu]

There is a process that needs to be performed to get the backlash right on the spider gears. Some special tools are required. With the 235hp the LMTV has even with a 1:1 hub ratio, I don't think top speed or fuel economy will be stellar and off road performance will likely suffer.

 

[coachgeo]

There is a process that needs to be performed to get the backlash right on the spider gears. Some special tools are required. ...

That was my wonder..... would the back lash stay same if hub could be removed as all one piece... if at all possible.

BTW... In case, I've miscommunicated. Seems am going to end up with two sets of Complete assembled hubs, and would be (if possible) swapping one complete set for another without disassembling the hub. The modified hubs can not be returned to stock even if it was wanted.

With the 235hp the LMTV has even with a 1:1 hub ratio, I don't think top speed or fuel economy will be stellar and off road performance will likely suffer.

As to off road at 1:1.... using modified hubs (A).... we agree, ...... would suck. was one of my points.

As to top speed not changing from total axle ratio of 7.8 with stock hubs to 3.9... with modified hubs..... beg to differ on that one; (or I miss understand you) that has got to make a big difference on top speed. MPG... not sure. Would think possibly if sat NOT at top speed but around 65. Now at 55mph it certainly should get better mpg cause it would take much less engine rpm to maintain it over stock Hubs (B).

 

[scottmandu]

As to top speed not changing from total axle ratio of 7.8 with stock hubs to 3.9... with modified hubs..... beg to differ on that one; (or I miss understand you) that has got to make a big difference on top speed. MPG... not sure. Would think possibly if sat NOT at top speed but around 65. Now at 55mph it certainly should get better mpg cause it would take much less engine rpm to maintain it over stock Hubs (B).

I'm guessing that the 3116 is most efficient at 1800 or so RPM.. However I'm not sure if enough torque is available at 1800 rpm to push the truck down the road at 70 mph. At lower speeds however fuel economy should be improved significantly.

Regarding the hub gears.. You cannot change the hubs realistically. This would imply changing of the spindle which is not something I'd do at the side of the road.

You could however setup the gears properly on each corner ahead of time and then swap them (shims and all) at a later time provided you don't get the corners mixed up. It's not terribly difficult to swap the bevel gears if you have everything shimmed properly to begin with.

 

[98G]

Fuel consumption is not directly tied to rpm. There's a sweet spot, frequently around 1600 rpm for many diesel engines. Running rpm higher or lower than this sweet spot will increase fuel consumption.

Also, changing gearing by such a huge margin is likely to have a good deal of unintended consequences.

 

[coachgeo]

Fuel consumption is not directly tied to rpm. There's a sweet spot, frequently around 1600 rpm for many diesel engines. Running rpm higher or lower than this sweet spot will increase fuel consumption..

.

That is my understanding as well. Apologize for not being specific. The 3.9 ratio would make the 1600-1800rpm sweet spot (most efficient point of engine in its power curve) to be closer matched to highway speeds than stock hubs.

....Also, changing gearing by such a huge margin is likely to have a good deal of unintended consequences.

That is my concern particularly when off road. Hub reduction reduces stress on the Ring and Pinion from what I understand. This then allows for designing in smaller R&P/pumpkin of axle housing like what seems to have been done on the LMTV. Thus using a hub setup offroad with hub reduction elimination creates much greater chance of breaking something in an LMTV's pumpkin... don't know about axle shaft issues. Another reason I wondered if they potentially could be swapped at camp site.

 

[tennmogger]

George, I think everyone is being courteous by not saying this: You bought someone else's experiment. He sold it at a cheap price, probably for a reason. Elimination of a reduction of 2 (half, etc) means your top speed (given infinite hp) would be twice normal, say 110 mph. Think we can all agree that choice was not well thought out.

In reality, with a 16k lb truck and only 225 hp, the LMTV is topping out on hp at just 55 mph with ORIGINAL gears. There has been reported much more lack of top end hp with the 3.07 pumpkins installed. With the doubling of speed per rpm, there is no doubt the truck will be sorely underpowered. Maybe it will be driveable on the flat on highway, and for that tidbit of information we eagerly await an honest road report.

Peak torque on the 3116 changes with intended design use but it's low, maybe 1600 rpm, so those speed-at-rpm numbers might not look bad. Since the ratio of speed to rpm is linear, 55 mph comes in about 1300 rpm. Most important, there's hardly any hp at that rpm, hp peaking out (leveling out really, check charts) about 2600 rpm, red line, so that's where you want maximum speed (and as designed originally).

Perhaps it will be drivable for puttering around, relying on torus slippage, probably held to top (direct) gear, 5th, staying out of overdrive 6 and 7, but bet the mileage (MPG) sucks, and there will be no acceleration.

Good thing you are getting a set of original hubs to swap back to. Concerning a complete change out of hubs at the beginning and end of a trail experience, you gotta be kidding? As they say, some dis-assembly required.

Bob

 

[coachgeo]

Tis logical info with data to support it. Thanks is exactly what was looking for. Will be interesting.

 

[Shark Bait]

In the mountains the little Cat is under powered already with the low gearing it has, empty. Take the gearing higher and put some weight on it and you're gonna run the kitty to death and the Allison will constantly search gears for a happy spot, all this builds heat, wear and tear. Then, "beside the road" you want to pull the hubs, fluid gotta go somewhere, dirt contamination, get the correct part to the correct corner, get the installation within tolerance, reassemble without leakage, refill lubrication with new, carry old lube to discard properly because it's contaminated, and get cleaned up to drive on to your next change out. Brother, I'm not peeing on your overland parade but I believe you will be creating yourself an experience of a lifetime that you'll not enjoy as well as if you did it at just 55mph. These trucks are fun but they have specific engineering on some things. I hope whatever you decide works for you and I by all means will follow it to see but I also like seeing things go good for folks in this hobby. Don't take me wrong, please, just giving you some things to think about owning mine for two years now.

Dave

 

[Lmtv772]

You guys might be off on the RPM you've posted. I know 95% of you won't have a tachometer installed (unless an aftermarket one). When I drive 40mph with my LMTV ,where everything is stock. the RPM are at 1800 in top gear.

 

[Retiredwarhorses]

I wouldn't want to be in an m1078 at 70mph...I get this very question weekly about HMMWV's, how can I make it go fast...these trucks were not designed for speed. They were designed for convoy speed and keeping up with tracked vehicles in various terrains. In the fist gulf war, the M1 Abrams and Bradley out paced the M113 so badly, they had to slow down. The problem was a a lot of them were ITV's, FIST-V and command tracks...

 

[tennmogger]

You guys might be off on the RPM you've posted. I know 95% of you won't have a tachometer installed (unless an aftermarket one). When I drive 40mph with my LMTV ,where everything is stock. the RPM are at 1800 in top gear.

No doubt you are correct. What is your engine rpm at full throttle? Speed at that rpm? Whatever the rpm, at WOT and max speed of 55 for a normal truck, Georges will be at 110 theoretically.

If your truck is going 40 at 1800, then 55 mph would be 2475, calculated. Is that close?

thanks

 

[Lmtv772]

I never noted it down , but I'll check next time. Got a 3 hour drive to do this week.

 

[Overdrive]

• set A hubs- (modified-3.9 total axle ratio) are great for Interstate highway cruising especially if going on a trip across half the country for example, BUT would suck for off road.
• Set B hubs- (stock 7.8 total axle ratio) are pretty good offroad, but Suck for interstate Highway travel. Granted these would be sorta OK for two-lane highway / taking your time and smell the roses traveling, but this is not a luxury one gets often these days.
• The fact I've end up with both out of the gate.

So for example If I was to say... go to Moab from OH with the Highway set installed then swap Hubs to the other set for few days on the trails..... then swap back again before trip home, life would be

I agree with what has been said on this topic already (I don't think I would want to drive my LMTV much over 60mph), however I am curious as to how this Hub A, Hub B setup is accomplished as far as different hub ratios... Did the seller describe or explain how he accomplished this? I originally assumed, when you mentioned "eliminated" the reduction hubs that there was some sort of drive flange installed to lock the axle shafts directly to the hub itself (like on a jeep with no lockout hubs) but it sounds like from your quoted description of set A/Set B, that different reduction gears were used. Seems like if there were a way to change the gear reduction ratios you could dial small changes into the final drive for a LITTLE more top end power without sacrificing too much torque but I am thinking its not that simple. Not too mention as described in another hub thread the tolerances and setup for the hubs requires precise measuring equipment.

Just pondering....
OD

 

[DiverDarrell]

Since he went to a 1:1 ratio at the hubs, the cheap easy stupid way is to weld the gears.