Semi-float or full float?

[dbryan]

Hey there, Just returned from moab, with a broken long side rear axle shaft. Managed to damage the locker as well.
Should I order the Polyperformance axles or go with a full floater? I have a line on a full floater for cheap, but not as cheap as the polyperformance axles. Any other suggestions?
Which set up would be stronger? I hate breaking stuff.
Thanks.

 

[crushers]

you hate breaking stuff then stick with the semi floater. no maintainence and ultra tough.
there are many more reports of the FF failing than the semi floater.
some here will disagree.

 

[Greg_B]

you hate breaking stuff then go with the full floater. Regular maintainence and ultra tough.
there are many more reports of the SF failing than the FF floater.
some here will disagree.

Corrected now

gb

 

[Greg_B]

Hey there, Just returned from moab, with a broken long side rear axle shaft. Managed to damage the locker as well.
Should I order the Polyperformance axles or go with a full floater? I have a line on a full floater for cheap, but not as cheap as the polyperformance axles. Any other suggestions?
Which set up would be stronger? I hate breaking stuff.
Thanks.

Now that my tongue is out of my cheek...

There are advantages and disadvantages to both set-ups, and it depends on your situation. Hows that for a rounded answer...

If you break a SF axle, your wheel comes off. If you break a FF axle, your wheel stays on.

If you run an auto locker in a FF axle, there are reports it loosens the axle bolts, creates play, then can shear those bolts and oblonge the dowel holes.

If you run an auto locker in a SF, it's an easy install (take off the back cover) and there is not the axle bolt issue.

If you anticipate running a factory e-locker or cable locker, you will need the FF axle.

There are fixes for the dowels and bolts. You can upgrade the number of dowels, and go with ARP studs. You can drill/tap the stud holes and go from 8mm to 10mm.

SF is much less maintenance. The bearings are lubed by the 90W gearlube, and seem to last many many miles.

FF is more maintenance, where you should get into the hubs at least once a year to re-grease, check bearings and reset the bearing load. I've heard that some Ozzies don't bother with the grease, and just run the bearings in oil (remove the axle tube seal), but have not confirmed if this is simply web gossip.

FF the weight of the vehicle is on the hub/bearings.

SF the weight of the vehicle is on the axle shaft.

As mentioned, there are pros and cons to both. I've not broke an axle yet, so obviously I don't wheel heard enough. That said, I know of at least two SF axles local to me that have broken, and the rear wheel has passed the truck on gravel roads. I know Crushers has had one FF grenade on him, on a road trip. I don't know the story completely, or maintenance schedule.

I have a SF in the rear of my BJ60 and left it there on purpose. I've a number of spare axle shafts, I have an auto locker, and I wanted low maintenance. They typically seem not a huge issue axle.

I have a FF on the rear of my BJ74, as it has cable lockers. I have a spare axle shaft, and do maintenance on it once a year. I also check the studs during the year. They seem typically not a huge issue axle.

HTH's and sorry I could not state clearer which is the better axle.

gb

 

[dbryan]

Thanks for the replies.

My truck is very heavy (7600lbs) and I run an air locker. I understand the the FF axle shafts are smaller diameter than the SF.
I know all about the wheel comming off. I c-clamped a hilift to my sliders and rear bumper to stop the wheel from comming off. Drove/winched 20 miles out over very rough terrain.
I would just like to know which will be stronger.
The SF with the Polypro axle shafts or
The FF.
thanks again.

 

[crushers]

the small part of the SF and the FF are the same size (where the axle goes into the center unit.
as for which will be stronger i do not have an answer for you. i have heard the FF axle shaft has more lateral twist movement to it and this was designed into it. the semi floater axle shaft due to the axle supporting the weight of the truck has little or now lateral twist.
if you already have the SF why not run the upgraded axle shafts. if they last then you are good to go, if they don't then upgrade to a FF later and see if it turns out to be your driving style that needs to change...
cheers

 

[Exiled]

I would run the upgraded axle shafts in the SF housing, and add rear disk brakes, which will keep your shafts from sliding out if you break them again....

Got any pictures of your truck? I'm curious to see a 60 series pushing that kind of weight!!

 

[Tinker]

If your truck is pushing 7600# you need a FF.

 

[dbryan]

Thanks again for all the advice.

I think I will upgrade the axles and see what breaks next first.

I had no problems over the last 5 years until I put the 3.05:1 in the transfer case - broke 2 smurfields (broke many birfields before that) - fixed with longfields - and now this. I guess it is the torque of the the 3b and the lower gears.

As for my driving style, I like to idle up stuff and not spin tyres. I am usually the slowest person in any group. Not too big a fan of mud ever since I almost lost my truck in Belize in a sink hole.

Sorry I am old school and have no digital photos of my truck yet.

Does anypne know of a trucking company that will ship a FF to
Canada for cheap?

Cheers.

 

[Mike S]

Thanks for the replies.

My truck is very heavy (7600lbs) and I run an air locker. I understand the the FF axle shafts are smaller diameter than the SF. ...I would just like to know which will be stronger.
The SF with the Polypro axle shafts or The FF.

DBryan

The design of the FF rear carries the weight of the truck on two sets of bearings, and not on the axle itself, so the SF axle must be heavier to carry the weight of the truck. The FF axle set has good strength - it's considered heavy duty. I ran a FF in my 60, but never beat it enough to break it.

Your SF air locker and thrid member can be used in the FF axle.

I do not know the details of the PolyPro axle shaft.

A side note - - I have a '47 Willys flatfender and converted the rear with a Warn FF and locking hubs. This set-up is extrememely strong, and allows me to dail out the hubs and flat tow the Willys with zero problems - another advantage of the FF rear.

M

 

[Mace]

The Poly Performance 4340 shafts will about double the breaking strength of your stock shafts. And allow more twist before failure. They are made out of a superior alloy compared to the stockers.

PP is the way to go.. if you test the breaking strength on a machine and compare the FF to the SF they will fail at approximately the same stress. FF's are nice but NOT that much stronger than the SF. Get the PP shafts and call it good..

 

[hks3sgte]

If your truck is pushing 7600# you need a FF.

x2... FF are designed for heavy loads. Take a look at any truck that carries any type of load... they have FFs...

 

[Mace]

"any type of load" = a lot more than a cruiser typically...

Where did the axle break? right next to the sidegear or at the flange. If it broke at the flange you can say the sheer weight of the 60 did the damage, if it broke at the diff, then it was power, not weight that broke it.

 

[The Dude]

I have never broken either.

I have a FF in my 61 that is repacked once a year and the studs are checked monthly. It also allowed me to run 5.29 gears with out grinding down any teeth.

I had a SF in my 40 that I never had any issue with, except when I grenaded my lock-right. The c clips dropped out and I had two axle shafts, with tires, come off the truck. PITA

I have since relaced the SF in the 40 with a FF out of a 45. It will get bigger ARP studs and larger dowels.

From what I have read, breaking strength is about even. It's what happens when they do break that made me switch over.

 

[HZJ60 Guy]

I have seen many many semi axles broken. The rear end starts hopping and snap. Semi's are a cheap and inferior design. All my rigs get full floater conversion kits to them. You shouldn't ask the DRIVE axle to CARRY the weight of the vehicle! Period!

 

[Mace]

I have seen many many semi axles broken. The rear end starts hopping and snap. Semi's are a cheap and inferior design. All my rigs get full floater conversion kits to them. You shouldn't ask the DRIVE axle to CARRY the weight of the vehicle! Period!

Funny, I have seen full floaters break when someone starts hopping too.


Almost ALL axles have the drive axles carying the weight. It is only in 3/4 or greater trucks that it is more common to have a FF design.

The axle shafts themselves are not inherently stronger. like I said, if you are snapping shafts out at the anle end I might believe you, but these shafts fail at the diff end ofthe axle. Where there is no stress form the tire.. unless you housing is bent and you have to bea thtem in with a hammer.

SF is fine..

 

[dbryan]

Sounds like I have opened up a can of worms.

Everyone seems pretty divided, which tells me that its probably 50/50 with advantages/disadvantages to both.

FF sounds nice, but I think I will go PP. I will have to SO the FF, plus it would cost me around $500 more than PP

My axle broke approx 2" from the splines and it was an uneven shear.

Thanks again.

 

[baldredhead]

for those that have FF and put in larger studs and dowel pins is there a writeup on that anywhere?

what about the cone washers? deleted?

 

[Exiled]

I have seen many many semi axles broken. The rear end starts hopping and snap. Semi's are a cheap and inferior design. All my rigs get full floater conversion kits to them. You shouldn't ask the DRIVE axle to CARRY the weight of the vehicle! Period!

I guess that's impacted by the type of wheeling you do. I spent many years doing expedition-style wheeling with *grossly* overloaded Land Cruiser wagons and NEVER saw a broken rear axle (all SF).

Toyota spec'd SF rear axles in many Third World markets, so I don't buy the argument of "cheap and inferior". A FF might be a better design for very heavy trucks, but that doesn't mean a SF won't stand up to serious abuse.

 

[dd113]

I perfer FF for every situation but cost/hassle needs to factor in. Biggest plus of a FF is that pretty much no matter what breaks you will still roll home. SF is jsut not like that even with the disk conversion. Blow your third and a SF is stopped. Blow a 3rd in a FF pull your shafts and continue on in front wheel drive.

I did the write up on POR. It is the somewhere.