Definitive conclusions - Which rear axle is best to disable and how?

[Sweet Rides]

Hi guys,

I`ve read varying opinions on this, but some of these are from many years ago.

So, I was wondering what the current thoughts are on this please and why?

1) Which of the two rear axles is best to disable in the Deuce if you are looking to get better fuel economy and less tire wear?

2)Why is this axle the preferable axle to disable?

3)What is the best way to disable it? If its the forwardt rear axle obviously it`s a removal of one of the splined axle shafts, but surely its better to remove both shafts so nothing moves. If its the rearmost of the two rear axles, is it best to remove the drive shaft or to remove the splined axle shaft(s)

Thoughts please and why? I`m sure some people must have been running one of these options for many years now, so would like to hear pros and cons of the options. thanks.

 

[INFChief]

Hi guys,

I`ve read varying opinions on this, but some of these are from many years ago.

So, I was wondering what the current thoughts are on this please and why?

1) Which of the two rear axles is best to disable in the Deuce if you are looking to get better fuel economy and less tire wear?

2)Why is this axle the preferable axle to disable?

3)What is the best way to disable it? If its the forwardt rear axle obviously it`s a removal of one of the splined axle shafts, but surely its better to remove both shafts so nothing moves. If its the rearmost of the two rear axles, is it best to remove the drive shaft or to remove the splined axle shaft(s)

Thoughts please and why? I`m sure some people must have been running one of these options for many years now, so would like to hear pros and cons of the options. thanks.

I’ll take a stab at this. Maybe I don’t understand the questions but here it is anyway.

First, in my State, you may not modify a vehicle unless you & the modifications meet certain criteria.

That aside; if you Remove the rear axle you are changing a number of characteristic to include center of gravity, stability, handling characteristics, and load capacity.

If you remove the center axle you’re faced with making or buying a long drive’s - and maybe a carrier bearing. Unless you remove the trunion and put dedicated spring packs on the remaining axle assembly I don’t see how you could gut the center differential and remove the hubs and axles from the housing without fabricating some sort of means for that hollow axle tube to articulate as you drive over uneven ground/terrain.

Thinking this over “out loud” lets me better understand why people might “Bob” a deuce or 5 ton.


May I adk

 

[Sweet Rides]

I’ll take a stab at this. Maybe I don’t understand the questions but here it is anyway.

First, in my State, you may not modify a vehicle unless you & the modifications meet certain criteria.

That aside; if you Remove the rear axle you are changing a number of characteristic to include center of gravity, stability, handling characteristics, and load capacity.

If you remove the center axle you’re faced with making or buying a long drive’s - and maybe a carrier bearing. Unless you remove the trunion and put dedicated spring packs on the remaining axle assembly I don’t see how you could gut the center differential and remove the hubs and axles from the housing without fabricating some sort of means for that hollow axle tube to articulate as you drive over uneven ground/terrain.

Thinking this over “out loud” lets me better understand why people might “Bob” a deuce or 5 ton.


May I adk

Hi, thanks for your reply but I`m afraid you've misunderstood me.

I`m not talking about bobbing a Deuce or removing any axles from the truck.

I`m talking about removing the power drive to one of the rear axles - by doing so fuel economy and tyre wear will be improved.

My question is which is the best axle to remove drive to and why, and which is the best way to remove the drive, splined shafts (one or both?) 0r removal of rear driveshaft if the rearmost axle is chosen.

 

[Jbulach]

If you’re trying to improve fuel mileage by doing this good luck… but if you must try removing the rear driveshaft and blanking off both rear axle shafts, as well as the same on the steer axle, if you have an air shift transfer case, would have the best chances of any measurable results. It also depends on a lot on how you were driving highway versus city type?

 

[Sweet Rides]

If you’re trying to improve fuel mileage by doing this good luck… but if you must try removing the rear driveshaft and blanking off both rear axle shafts, as well as the same on the steer axle, if you have an air shift transfer case, would have the best chances of any measurable results. It also depends on a lot on how you were driving highway versus city type?

Hi, yes, have air-shift with free wheeling lock-out hubs on the front steering axle.

Tire wear and fuel mileage are both considerations.

Some people, in older threads, think its best to remove drive from the rear axle, others including Jatonka, think its best to remove drive from the forward rear axle.

I`m really trying to see who has removed drive from either rear axle, how they have done it, why they chose that axle and why they believe this works best.

My driving is all road, mainly around town but some highway too.

 

[NY Tom]

Hi guys,

I`ve read varying opinions on this, but some of these are from many years ago.

So, I was wondering what the current thoughts are on this please and why?

1) Which of the two rear axles is best to disable in the Deuce if you are looking to get better fuel economy and less tire wear?

2)Why is this axle the preferable axle to disable?

3)What is the best way to disable it? If its the forwardt rear axle obviously it`s a removal of one of the splined axle shafts, but surely its better to remove both shafts so nothing moves. If its the rearmost of the two rear axles, is it best to remove the drive shaft or to remove the splined axle shaft(s)

Thoughts please and why? I`m sure some people must have been running one of these options for many years now, so would like to hear pros and cons of the options. thanks.

I don't think you will save much on tire wear honestly. I have read mostly of people desplining the hubs on the front and rear axle. Some say that it is easy to get stuck even on wet grass if you are running that way. Others use a locking hub on one side rear only to help it turn a bit better. I cannot imagine pulling the driveshaft is going to do much.

 

[WOLF DOG]

I’ll take a stab at this. Maybe I don’t understand the questions but here it is anyway.

First, in my State, you may not modify a vehicle unless you & the modifications meet certain criteria.

That aside; if you Remove the rear axle you are changing a number of characteristic to include center of gravity, stability, handling characteristics, and load capacity.

If you remove the center axle you’re faced with making or buying a long drive’s - and maybe a carrier bearing. Unless you remove the trunion and put dedicated spring packs on the remaining axle assembly I don’t see how you could gut the center differential and remove the hubs and axles from the housing without fabricating some sort of means for that hollow axle tube to articulate as you drive over uneven ground/terrain.

Thinking this over “out loud” lets me better understand why people might “Bob” a deuce or 5 ton.


May I adk

INFChief, he's asking about removing the axle shafts, not the axle housing. No center of gravity, stability, handling characteristics, or load capacity change by just removing axle shafts. If I recall correctly, years ago there was an opportunity to buy front lock out hubs and a conversion kit to install a lock out hub on either side of the front rear axle which would ease the stress and binding between both rear axles while making turns.

 

[Sweet Rides]

Ok, NY Tom and Wolfdog, thanks for your input guys.

Let me expand on this a little :

Options for forward rear axle are to fit lock-out free wheeling hubs and "splined both ends" axle shafts to both sides of that axle. This is the perfect solution as it allows that axle to be completely free, but also to be re-engaged fully in a matter of a couple of minutes. The downside with this operation is that the parts are very expensive.

The above operation can also just be done on one side of the forward rear axle, halving the cost. Some have done this. But I don`t like the asymmetry and also believe there must still be drag/wear on the side which is not fully free wheeling.

There is also the option to disable the rear most axle by either doing the above, or by removing the short rear drive shaft. But that way you cannot quickly re-engage the rear axle if needed and the axle internals/diff are still turning and creating wear/drag.

The consensus I found, doing a search on this forum from years ago, was that if you disabled the rear most axle, the truck would get stuck just on wet grass. Jatonka reported that he had tried this, and didn`t like the result.

He went onto reconnecting the rear axle and instead, removing both splined axle shafts from the forward rear axle instead and capping those axles off with stock front axle end caps. This way the forward rear axle is truly free wheeling and the drive goes through to just the rearmost axle. Combined with lock-out hubs on the front axle, you still have 4x4 if needed and apparently the truck has less inclination to get stuck if the rearmost axle is still receiving drive anyway. He was pleased with this set up.

All of this was about 15 years ago I think. So I`m wondering, with the testing of time of these various options, which one proved to be best in the long run and why? Useful info I think.

 

[Gypsyman]

I could be way off here so bear with me.

I was just staring at the design of the rear suspension. In my mind it seems that since the forward drive axle is ahead of the trunnion (pivot point) when it is being driven it would be trying to lift or climb ahead of the trunnion. Under torque it would appear that the rear drive axle (being behind the trunnion) is driving itself down into the road surface. The downward force of the rear drive axle would be counteracting the lifting force of the forward drive axle balancing them out.

With no power to the rear drive axle I can see where there would be an opportunity for the forward drive axle to want to hop under power, or at the very least have less down pressure for traction.

I seem to recall an old thread where a member had the rear drive axle disabled. On a bumpy section of highway the forward drive axle was hopping up when encountering large bumps in the road and shock loading the transmission which I believe he stated contributed to a transmission failure.

One of the engineering minds needs to jump in here...

 

[G744]

IMO, this is an idea in search of a problem.

Nope.

DG

 

[cattlerepairman]

My understanding of the geometry of the rear suspension of the Deuce is also that disconnecting the FORWARD REAR AXLE is the preferred option. This is different from "regular" over-the-road trucks where the middle axle is usually the driven one and the rearmost one is un-powered unless locked in via power divider.

In the Deuce, lock-out hubs (AVM for example) and a splined axle shaft are options. There is debate about one side vs both sides (to prevent the spider gear from spinning), or just pulling the shafts and putting blank covers on etc. but the principle is the same.

I would add that, with only the rearmost rear axle driven, the truck is mostly relegated to staying on asphalt; members have become hung up on speed humps in a parking lot in that configuration.

For this reason, a modification that allows the non-driven axle to be locked in quickly might be preferable. In fact, a differential locker (Detroit, Yukon, ARB) in the rearmost differential would probably be useful. Yes, one can lock in the front axle as well.

I have looked at this in some detail in the past and, for my usage case, decided that it was not worth doing. Your mileage may vary.

 

[cbrTodd]

I replaced the left mid axle shaft on my deuce with an old front splined cap for a while. In my case it was an attempt to lessen the amount of tire scrubbing that I saw when making tight turns on pavement. It did seem to do that, not a huge change but it seemed like the black marks on the road got smaller. It also caused me to have to lock in the front hubs and axle on one particularly steep gravel driveway in order to make it up the hill. With an open differential it is essentially one wheel drive with only one rear axle powered. I have since reinstalled the axle shaft.

If you do choose to do this, you only need to de-couple one side of the axle as long as you don't have a locker installed. The open differential takes care of the rest. The spider gears will remain static when you are going in a straight line, and there will be negligible force on them when you turn. And don't expect any fuel economy improvement, as everything will still be spinning approximately the same speed as before as long as you have a drive shaft connected to the axle. The only way to have anything not be spinning, like what is done with lock out hubs on the front, would be to remove the driveshaft to the rear most axle and remove both axle shafts from the rear axle. Which seems like far too much work for the minimal fuel economy gain you might get.

 

[fleetmech]

fwiw, I feel like there would be a lot more mileage gained from switching from ndt to a modern style truck tire, especially with the hubs flipped running singles.

 

[rustystud]

fwiw, I feel like there would be a lot more mileage gained from switching from ndt to a modern style truck tire, especially with the hubs flipped running singles.

YES ! Exactly. All this talk about which axle to disable for better mileage is really just academic. Basically gets you nowhere. The whole geometry of the rear axle assembly is geared (no pun intended ! ) for both axles to work in tandem . That is why you cannot disable one without causing problems. Like cattlerepairman mentioned, over the road "Semi-Trucks" can and do disable the rear driving axles . They are designed for this. The Deuce is not. Disabling the front axle is a good option though, and you get better steering feel.
Fleetmech has the best answer though for mileage. Replace those tires with good over the road "high mileage" tires ! That and your overdrive transmission should help more then any rear axle disabling.
Also keep your Multi-Fuel in tip top shape. That means regularly replacing/cleaning your injectors, and adjusting the valves. For some reason most people fail to realize that injectors are only good for 10,000 to 50,000 miles, depending on injector. Then they start to plug up with carbon and other gunk. At "King County Metro" we would replace injectors every 10,000 miles. They where sent out and cleaned, and reused many many times.

 

[Sweet Rides]

For me, I like the "stock" appearance of a Deuce. I`m not personally a fan of Bobbed Deuce`s and I also think they lose their much loved style when super singles are fitted.

Even just putting on non-bargrip road tyres, really changes the look of the truck and for me, it`s a quite negative change visually.

I would like to change to 11.00-20 bar grip tyres for better cruising gearing, and also small mpg gains too. New or Second hand, these simply are not available anywhere in Europe. So the option is to import 11 new tires from the USA. I think with purchase , shipping and taxes this will run over 10,000USD for the 11 tires to my door. Ouch!

So, the consensus is that Lock-out hubs on the front axle, which I have, are a definite improvement in a few different areas and no negatives.

As for the rear axles, I`m getting the vibe that disabling one would see only very very small MPG gains, but would see some small, less tyre scrubbing gains.

At present, with what`s been said so far, I`m leaning towards leaving the rear axles "as is" in total stock format. Unless someone feels that the tyre wear/scrubbing is greatly reduced.

It seems that the consensus is, that if one axle is to be disabled, its better to disable the forward rear axle, because by disabling the back rear axle traction can be lost more easily, even on something simple like wet grass.

 

[HDN]

Interesting idea with the tires. I've read about tires alone making a difference in fuel efficiency with daily drivers. It makes me wonder what the fuel efficiency comparison is between running ten NDTs compared to running ten OTR truck tires, or even Michelin XZLs of the same size...

That said, I wouldn't pull drive shafts or de-spline axle shafts. I drive it for what it is - an old military tactical vehicle. Though every time I hop in it I'm not on any particular errand or mission, so I don't have the need to go fast - just enjoy it and get all those smiles per mile If I want something to go faster and carry stuff, I'd get a civvy pick-up truck or a 1-ton van.

 

[Jbulach]

The problem with replacing tires is that you will never recover your cost in fuel savings. Drive and enjoy your truck as much as you can afford, when your tires “need” replaced, then it may be worth evaluating a better replacement.

 

[Sweet Rides]

Interesting idea with the tires. I've read about tires alone making a difference in fuel efficiency with daily drivers. It makes me wonder what the fuel efficiency comparison is between running ten NDTs compared to running ten OTR truck tires, or even Michelin XZLs of the same size...

That said, I wouldn't pull drive shafts or de-spline axle shafts. I drive it for what it is - an old military tactical vehicle. Though every time I hop in it I'm not on any particular errand or mission, so I don't have the need to go fast - just enjoy it and get all those smiles per mile If I want something to go faster and carry stuff, I'd get a civvy pick-up truck or a 1-ton van.

The idea is not to go faster.

The idea is :

1) to try to reduce unnecessary wear/drag on the tyres and drive train components - when the truck is just being used for road use.

2) To get better MPG on the road AND to get Lower RPM`s at cruising speed and/or increase cruising speed at the same RPM`s. If the same cruising speed is maintained, say 52mph, but the tyres are changed from 9.00`s to 11.00's, then the RPM`s at 52MPH will be lowered by say, a couple of hundred RPM`s, and this has two benefits - better MPG AND less engine wear/stress.

There is no doubt, that changing from 9.00 to 11.00 NDT`s is going to give you a higher cruising speed AND/OR better MPG. But, the offroad ability of the truck will be greatly reduced due to clearance issues.

The same effect can be achieved, as you correctly say, by switching to a radial road tyre with the same diameter as an 11.00-20 bias ply tyre.

For me, I have to stick with the full profile, bias ply, bar grips - as I just like the look of them so much and feel they "make" the truck aesthetically. I have the option of going up to the 11.00`s, which is what I really want to do and I think it looks sick! But it`s just gonna cost a LOT of money to do it...

 

[Sweet Rides]

The problem with replacing tires is that you will never recover your cost in fuel savings. Drive and enjoy your truck as much as you can afford, when your tires “need” replaced, then it may be worth evaluating a better replacement.

Totally agree. Luckily my 9.00`s are 40+ years old and are very perished and DEAD, so I`ve got to get some kind of new tyres anyway.

 

[Sweet Rides]

This is the exact look I would like to achieve, original styling but has the subtle difference of the 11.00-20 bias bar-grip tyres for better cruising speed or lower RPM`s and better fuel economy etc.