Full Floater vs. Semi-Floater Axles (1 Viewer)

[TemboTusk]

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I have a 27 year old Cruiser and parts will break; it’s an old vehicle. Ever since I broke an axle, I worry about this being the latest weak point. The fact that I have replaced my broken axle shaft with an equally old axle does not help! Am I worried for nothing?


Seeing as Full Floater Axles in the US are very hard to find, would it make sense to beef-up a semi-floater axle with modern chromoly axles shafts or pursue the near unobtainable or at least very expensive FF?

One concern was not being able to drive off the trail. With a broken axle in a semi-floater you are dead in your tracks. Another concern is the slippery slope. If I beef up the axles, what is next?!! .

..

 

[TS888]

Not dead -- You have front wheel drive. Pull the rear drive shaft to keep the damage to the axle to a minimum. Chances are any bits of metal will not hurt the 3rd with the drive shaft not trying to spin it.

 

[klinetime574]

here goes.....


if you did any rock crawling, then i would'nt install a FF rear if you paid me to.

yes, the weight carrying capability is better when it comes to a FF rear. however, how much weight are you going to pile in your 60? if a sf rear in a similar seized rig ( with a 450hp supercharged vortec ) can hold up just fine, then why would you want to change it?

when's the last time somebody on here broke a sf rear? i bet it's well below 1%. well below.

now ask the guys that run ff rears. i bet more than 50% of them have broken shafts. even the "better" poly shafts. most people with FFs carry spare shafts. guys with SFs don't.

silly. just plain silly. i would'nt run one in my rig.

if none of that convinces you, then how about this: how many miles are on your 60? 260 plus thousand. right? when's the last time it had a rear axle issue? ......... yup. i'll stop now.

georg

I quoted this from another thread. Follow it with the blue square.

I wouldn't worry about putting in a used axle shaft.

 

[snowboardonsnow]

Not dead -- You have front wheel drive. Pull the rear drive shaft to keep the damage to the axle to a minimum. Chances are any bits of metal will not hurt the 3rd with the drive shaft not trying to spin it.

Your axle will fall out

 

[TS888]

Your axle will fall out

And... I'm a dumbass!

Yes, yes it will. It will shimmy right out of the damn casing and leave you dragging ass.

I officially apologize to the 'Mud masses. I spent too many years driving Land Rovers (all FF axles).

 

[snowboardonsnow]

Its OK as long as it was a d90 or d110 hahaha ;p

 

[lcwizard]

Theoretically since the minimum diameter is the same they should break under the same load if materials are the same. I've broke one semi float , right at the spline, at the minimum diameter. The full floater shaft is a constant diameter end to end where the semi-float tapers from about 1 7/8" to 1.3" at the spline. Given the same materials they both will twist the same until yield.
The constant diameter shaft will twist along it's entire length before yielding where the taper shaft will
twist until yield at only the short section near the spline at the minimum diameter. Many times you'll see a floater axle with a stripe painted down it's length. That informs the owner as to the amount of twist that axle has undergone through it's life and a good indicator of it's future lifespan. That stripe may start at the 12 o'clock position at one end and end up at the three o'clock position at the other on a well used axle. Since the s/f shaft twist is restricted to such a small section you can't apply this technique. That same twist applied to such a small area will just snap the shaft with no warning.
Unfortunately the floaters we get in the USA are hand me downs with who knows how many miles and
probably ran behind diesel motors in the outback while the s/f shafts in the US that spent 98% of their
life running down paved freeways from soccer fields to the local ice cream shop. A fair comparison
is difficult between the two. Theoretically the floater should be better. What you'll score as a used assembly from an importer might just be worn out.

 

[snowboardonsnow]

Don't you have to factor in the fact that even if the shafts were the same (as Lcwizard just said they are not though) One has only torque applied and the other has torque applied plus X amount of weight. So the Semi would snap sooner.

I know what George is saying, specially state side if you start breaking axles because you are really wheeling hard (or not wheeling it right "hammer down B itch!") then there are better easier stronger cheaper options here although you will have to stray away from Toyota.
Its just not cost effective for us mild wheelers to buy and use ff's. Man I would still love to have on though haha.

Just carry some spares and then you won't have the worry holding over your head.

 

[Toadhopper]

Moly Semi-Float

I'm wondering how anyone would compare the strength a moly SF axle to a stock FF axle shaft?
It seems like going FF with new moly axles would be the best of the best, but I was also wondering if many of us break moly SF axles with a 2F, or even a moderately built V8?

 

[snowboardonsnow]

Thats a good question and I am sure a hard one to compare. Weight for the semi, and how old the ff is probably plays a huge part and would be hard to test.

I don't know but I think you are hard pressed to break a moly with a 2f I am sure it can be done specially if you get down below 100:1 gearing but I would think with a 2f and a broken moly axle you were probably wheeling pretty aggressively.

I hope someone can chime in who knows though, because I am just speculating.

 

[lcwizard]

Don't you have to factor in the fact that even if the shafts were the same (as Lcwizard just said they are not though) One has only torque applied and the other has torque applied plus X amount of weight. So the Semi would snap sooner.

I know what George is saying, specially state side if you start breaking axles because you are really wheeling hard (or not wheeling it right "hammer down B itch!") then there are better easier stronger cheaper options here although you will have to stray away from Toyota.
Its just not cost effective for us mild wheelers to buy and use ff's. Man I would still love to have on though haha.

Generally a broken axle during wheeling is a result of twisting loads. Weight will have little to do with it since most of us are operating well within the rated shear
capacity of the stock axle. Semi floats seldom break because of weight. They will break if the bearing surface gets so bad that the bearing and axle fail from heat.
This is usually at a higher speeds where heat can develop. They will also, assuming the first scenario doesn't occur, eventually work harden at the bearing surface from the pounding between the road and truck. At that point the steel develops a crystalline structure and becomes brittle. This doesn't occur often in a stock axle because the manufacturers use a material designed
to have a long lifespan under these conditions and will usually wear out in the first way before this occurs.. This is why good axle builders don't use chromoly in a semi float application. It works very well in a full float where it doesn't feel the millions of cycles of road noise. Moly is stronger but work hardens faster than the stock material so it's better applied to a floater where it only is subject to twisting loads. There are better materials for a semi float and
I'd discuss this with a real axle builder like Marc Williams, Moser, Summer Bros
or the like. Also beware of import Chromoly. Would you buy your sick mother an oxygen system made in China?

 

[T-bones 60]

My LC is 28 years old and the last thing I ever worry about is the beefy axles breaking! In my reading hundreds of posts on Mud I can only recall a couple of people breaking axles. Those were guys running 35's or larger and wheeling very hard. I think Georges post says it all above. Anything can break, but one of the things Land Cruisers are famous for is their axle and drive train strength. I myself wouldn't bother spending the $ on a FF.

 

[Tapage]

I have to broke SF splines in my desk .. that was with my old 37" chained and locked .. last time I broke one was in the middle of nowhere ( that it's really nowhere in a 3rd wold country ) but thanks to my rear disc setup I where able to drive Tencha back to civilization by her own power ..

I'm not on polys ... still happy with 'em .. although it will be fantastic have FF with some sort of 4340 axle on it ..

 

[Dazed]

OK so if one has SF and doesnt have rear disk brakes, is there anyway to drive a truck that has a broken rear axle without replacing the axle? What options are there?

 

[ntsqd]

For me the cost of replacement axles (one was bad due to the bearing killing it and the other wasn't so good) was nearly that of a FF assembly less the diff (at the time) so I got one. I'm going to center the diff for my v-ate swap, so buying SF axles then would have just meant that I would have to buy another set in a year or two.

A SF axle shaft has a multitude of destructive forces all located at the transition from shaft to flange. Add in the surface hardening that has to happen for the inner race-less, C-Clip type rear wheel bearings to work and it's a potent recipe for disaster. That they last as long as they do is a minor miracle.

A tapered shaft still twists, but how much it will twist at any given point along the taper depends on the twisting force and the OD of the shaft.
Said differently, a straight shaft will twist uniformly over its whole length while a tapered shaft will twist progressively less as the OD of the shaft increases.

In mild steels you get a nearly unlimited fatigue life. Not so in any variety of the Chro-Mo type steels. They are stronger to much stronger, but their service life will be shorter if you are using them to full advantage. As the number of cycles goes up the life-span goes down. Not something that is usually said about mild steels.
FWIW all steels have a crystalline structure. Good quality steels have a very fine grain size, poorer quality and less refined steels will have a larger grain size.

 

[TemboTusk]

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Strong opinions for both sides.

For those of you who have switched over to Full Floaters, would you do it again given the chance?

Klinetimes574, thanks for the link to that other thread. Very interesting read.

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[lcwizard]

For me the cost of replacement axles (one was bad due to the bearing killing it and the other wasn't so good) was nearly that of a FF assembly less the diff (at the time) so I got one. I'm going to center the diff for my v-ate swap, so buying SF axles then would have just meant that I would have to buy another set in a year or two.

A SF axle shaft has a multitude of destructive forces all located at the transition from shaft to flange. Add in the surface hardening that has to happen for the inner race-less, C-Clip type rear wheel bearings to work and it's a potent recipe for disaster. That they last as long as they do is a minor miracle.

A tapered shaft still twists, but how much it will twist at any given point along the taper depends on the twisting force and the OD of the shaft.
Said differently, a straight shaft will twist uniformly over its whole length while a tapered shaft will twist progressively less as the OD of the shaft increases.

In mild steels you get a nearly unlimited fatigue life. Not so in any variety of the Chro-Mo type steels. They are stronger to much stronger, but their service life will be shorter if you are using them to full advantage. As the number of cycles goes up the life-span goes down. Not something that is usually said about mild steels.
FWIW all steels have a crystalline structure. Good quality steels have a very fine grain size, poorer quality and less refined steels will have a larger grain size.

Yes to all but you may be getting too technical so that your explanations are rejected . Few will understand why I choose mild steel over chromo or even DOM in cages and other chassis accessories. I prefer the unlimited fatigue life
over the bragging points.
Perhaps the crystalline explanation wasn't the most precise definition but I'm
not sure how else to word it. Maybe the change in grain is better? However it's
said the result is that the axle gets more brittle and failure follows?
In a tapered shaft the twist is less perceptible because the failure occurs before the larger diameter shows deformity.
By the way, I look forward to your posts. You appear to have an engineering
background. Either that or you stayed at a Holiday Inn Express last night.

 

[TS888]

Calling again on my (apologies) Land Rover history -- LR guys covet Toyota axles. One of the most popular mods for LR axles is Toyota 3rds and and upgraded axle halves, and Toyota-style birfs to replace the LR parts.

And yet, many people (me among them) never broke a LR axle in years. I've never been a hard core wheeler, so that helps, but as others have mentioned, a little mechanical sympathy goes a long way. And, even a SF axle is not that hard to swap on the trail. Yes, you will need to carry gear oil and a spill kit, but it's still a job you can accomplish in an hour with basic tools.

 

[TemboTusk]

Calling again on my (apologies) Land Rover history -- LR guys covet Toyota axles. One of the most popular mods for LR axles is Toyota 3rds and and upgraded axle halves, and Toyota-style birfs to replace the LR parts.

And yet, many people (me among them) never broke a LR axle in years. I've never been a hard core wheeler, so that helps, but as others have mentioned, a little mechanical sympathy goes a long way. And, even a SF axle is not that hard to swap on the trail. Yes, you will need to carry gear oil and a spill kit, but it's still a job you can accomplish in an hour with basic tools.

TS, you are right, the actual R&R of the axle was not a major issue. However, there was a bit of collateral damage that added to the mix. The outer bearing was destroyed and without a bearing puller and a new bearing, the new axle would not go in. I was lucky in that the carrier bearing looked OK and got me home. Upon closer inspection once back home; it turned out the carrier bearing did get damaged significantly.

I don't know what issue take place when a FF axle breaks, but a SF axle break seems to take out the at least one bearing.

.

 

[Slowerthanu]

Build your own FF.

Buy the flanges from Ruffstuff

Buy a used front disc/ knuckle setup from a 60 series.

Bolt on spindles, brakes, calipers and measure for axles.

Wait for axles, install assembly.

Now you have a full float and matching components all around.

Make sure you install a proportioning valve because your rear brakes will be very capable.

Also, the dreaded Chinese importer Trail Gear now makes new hub housings, drilled for extra dowels AND new spindles, all constructed from the dreaded Chinese chromoly. I have decided to wait until these are tested until I run them, although my trunion eliminator and 6 shooters kick some ass.

Dan