Semi-floating Vs Fully-floating diffs.

Submitted: Saturday, Mar 13, 2004 at 20:48
ThreadID: 11222 Views:7227 Replies:9 FollowUps:5
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Well I've just found out how maintenance unfriendly a semi-floating rear diff is. I wanted to replace the L/H rear hub seal and check the bearings on my GQ Patrol because of a binding brake caliper (the hub got very very hot ). I have this thing about preventative maintenance. Anyway I took the axle out which is pretty straight forward, and found the mother of all nuts (58mm) up against the inner bearing which is torqued to around 440-490 Nm! I've now had to make a special spanner using a 58mm socket which I cut in half, welded onto some 10mm flat bar with a hole cut in it, enabling it to slide up the axle and onto the nut. I then welded the 3/4 square drive end 12" along the bar so as to torque it up again. Its very fortunate that I have access to a machine shop and good tooling to do the job or it could have become a real nightmare. This is certainly not a job that can be performed easily in most peoples sheds let alone in the bush if you had a failed wheel bearing or heaven forbid a broken axle. At least with a fully floating diff you don't require any special tools or 6" offset vises or hydraulic presses or 3/4 drive torque wrenches to do the job!
Do semi-floating diffs have any advantages over fully-floating ones or is it just a means for car manufactures to earn more money through maintenance because they know 99% of people can't do the job themselves?
This is certainly one case where Nissan require a good reaming!
Give me a fully-floating diff any day!!!
Cheers... I needed that beer.
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Reply By: Member - Bob - Saturday, Mar 13, 2004 at 21:18

Saturday, Mar 13, 2004 at 21:18
very impressive. Wouldn't mind someone with your skills tagging along on my next trip.

A bit unkind to Nissan - they probably have semi floating diffs to improve traction during river crossings. I can imagine if your diff floated the whole vehicle could float down stream.
AnswerID: 50227

Follow Up By: Peter 2 - Saturday, Mar 13, 2004 at 22:05

Saturday, Mar 13, 2004 at 22:05
LOL love that, must bring that up at the next driver training session!
FollowupID: 312052

Reply By: Savvas - Saturday, Mar 13, 2004 at 22:41

Saturday, Mar 13, 2004 at 22:41
For us that are diff challenged, what is the difference between a fully floating and semi-floating diff anyway?
AnswerID: 50243

Reply By: desray - Saturday, Mar 13, 2004 at 22:53

Saturday, Mar 13, 2004 at 22:53
It should be semi-floating or fully floating AXLE not diff. A fully floating axle is on the 80 series toyota , you can remove the inner rear drive axles without removing the wheels, good if they break you can still drive the car. The semifloating is like the patrol the rear inner drive shaft/half shaft as called is what the wheel is bolted to.If it breaks you have no drive at one end or no wheel at the other.
AnswerID: 50245

Reply By: ianmc - Saturday, Mar 13, 2004 at 23:06

Saturday, Mar 13, 2004 at 23:06
Perhaps someone who is more mechanically savvy could tell us how many 1990's onwards makes/models have the full floaters.
My fathers Austin A30 in the 1960's had full floaters. Just as well as it broke a couple but they were a cinch to change over.
An old 1960's Inter aa120 also had full floaters.
The Troopie hubs look like full floaters which surely arent much more expensive to build?
AnswerID: 50248

Reply By: flashnick - Saturday, Mar 13, 2004 at 23:31

Saturday, Mar 13, 2004 at 23:31
Nugget, its good to see you are resourceful enough to remove that lock nut.

I think your problem may have been caused by an overtight bearing. - the heating and cooling just making the problem worse.

Rather than blame Nissan/Semi floating diffs I think you should consider that whoever serviced that part of your vehicle last didnt know what he was doing OR misread the technical manual, - the locknut should be tightened and then backed off.

I must say I always find Japanese 4WDs to be easy to service in the field. - Only have problems with 'poorly' serviced vehicles.

AnswerID: 50252

Follow Up By: nugget - Sunday, Mar 14, 2004 at 18:08

Sunday, Mar 14, 2004 at 18:08
The manual actually states to tighten the nut to 441-490 Nm. This must be built into the design to ensure the axle sits in the right place because with a semi-floating type design the bearing is pressed onto the axle (interference fit) hence the use of a hydraulic press to remove the axle from the bearing housing. The method you described is correct for a fully floating type axle.
I'm still blaming Nissan!
FollowupID: 312107

Reply By: V8troopie - Sunday, Mar 14, 2004 at 02:38

Sunday, Mar 14, 2004 at 02:38
Interesting description there Nugget, only thing is I cannot see why you had to cut the 58mm socket in half??, maybe I'm missin something here.

I had s similar spanner problem a while back when I decided to service the front wheel bearings of my troopie. It too required a socket, much larger than the ones in my tool box, to undo the bearing nut. The previous mechanic apparently used a dift or a screwdriver to hammer it tight, as was evident on the nut!
My solution for the spanner was a bit more agricultural but it too worked. Found two short bits of angle iron and hammered them out a bit so they corresponded to the nut edges. Welded them 180 degrees apart on a short piece of suitable pipe to make a spanner that gripped the nut at two places. Welding on a bar for a handle completed the job.
No torque wrench I'm afraid, I dont own one. Used mark one eyeball method to torque the nut as per manual then back it off for the correct wheel drag.

AnswerID: 50260

Follow Up By: nugget - Sunday, Mar 14, 2004 at 18:38

Sunday, Mar 14, 2004 at 18:38
The reason for cutting the socket in half is that the nut is actually on the inside of the hub. that is it is slid over the axle up to the inner bearing. The axle is actually stepped with 3 different diameters along its length.
Up near the hub it is nearly 1.75". The axle is threaded at this point where the nut screws onto it. Therefore I needed to cut the socket in half to enable it to be slid up the axle onto the nut. Your Troopie has fully floating diffs front and rear. The Patrol does have a fully floating front diff where servicing is done the same way as you described with your Toyota.
FollowupID: 312112

Reply By: Charlie - Sunday, Mar 14, 2004 at 10:27

Sunday, Mar 14, 2004 at 10:27
I’ve made a pipe wrench by hammering a large nut (plumbing fitting) into a piece of exhaust pipe, works fine for replacing the nut but not strong enough to remove it. You could probably strengthen it with a bit of welding but I just use a hammer and cold chisel to tap the nut off. Seems to be a common way of doing things. As usual car manufacturers love the semi floating diff because it's cheaper.

Regards Charlie
AnswerID: 50275

Reply By: Phil G - Sunday, Mar 14, 2004 at 11:20

Sunday, Mar 14, 2004 at 11:20
Semi floating on most 4wds is a no-maintenance item - bearing is lubed by diff oil. Breakage is extremely rare on most vehicles.

Fully floating require a greasy wheel bearing service every 20 or 40k. This often gets neglected, and I've assisted people with seized rear bearings in the desert on fully floaters. Most fully floating Landcruisers share the same bearings/seals F&R.

All Prados, hiluxes and 100 series with IFS, now have semi-floaters.
AnswerID: 50281

Follow Up By: nugget - Sunday, Mar 14, 2004 at 18:21

Sunday, Mar 14, 2004 at 18:21
The rear bearings on the Patrol (semi-floating) are lubricated by grease not the diff oil as you suggested because they have a inner axle seal to prevent oil going into the hub. I was thinking about removing it and letting the bearings run in diff oil but looking at the diff level plug I thought it was a little low to allow much oil into the hub and would also require drilling holes or cutting a slot into the lip that the inner axle seal sits against to allow oil past.
FollowupID: 312109

Follow Up By: Ralph2 - Tuesday, Mar 16, 2004 at 18:40

Tuesday, Mar 16, 2004 at 18:40
As usual Phil G talks about thinks he knows little about, this time lubed by diff oil, breakage extremely rare CRAP.
FollowupID: 312362

Reply By: sails - Sunday, Mar 14, 2004 at 21:20

Sunday, Mar 14, 2004 at 21:20
just another note on the topic. We passed a seven vehicle "tag along tour" stopped on the side of the road from Nhulunbuy last year,due to a Mazda (?)4 X4 ute with a collapsed rear wheel bearing. Vehicle was fitted with a semi floating axle system as was our '98 Rodeo 4X4. The Mazda couldnt continue or it would break the half shaft ,as the load was transfered on to it once the bearing collapsed. Lots of satphone calls and waiting for a flatbed tow to come out from Nhulunbuy. I had a slight leaking oil seal on the passangers rear wheel, so decided to do the repair while in Nhulunbuy, just in case. Was faced with the same problem as Nugget regarding removing the big nut, and then removing the bearing. Fortunately one of the local mechanics had faced a similar problem before and had made up a special tool ,cutting the socket and inserting a long length of 2 " water pipe . He used his rattle gun to remove it. Along with needing a press to remove the bearing, it showed how un user friendly that system is for a bush vehicle.No way I could do it on the side of the road. The torque on the bearing was high, cant remember the numbers, but the lock nut tightens up on the inner shell only. The bearing free play is pre set with shims. I prefer the old toyota or land rover fully floating system where you could remove a half shaft and still have a wheel on the axle that you could travel with.
AnswerID: 50327

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