Got a Fuso. It was sweet. Then it broke.

ctane

New member
Greetings,

After deciding a Fuso FG fit my needs for a work truck I lurked hard on this forum and learned much. I found a '98 FG with 77k on the odo, took a risk on the rust situation and flew to Ohio to buy it. I live in Washington state and drove it home. 2500 mi. PO was using it as a service truck for his excavation company and I guess it was frequently parked on jobsites for long stretches, thus the low miles.

The drive home went great until we hit some snow in Wyoming and needed to run in 4wd for about 30 mi. I got out, locked the hubs, got back in, shifted transfer case into 4hi and away we went. The roads were pretty slick and dark so top speed was about 40mph, several times we hit stretches of dry pavement and I slowed and shifted transfer case back to 2hi and then back into 4hi when it got snowy again. After about 3 cycles of this and about 30mi we dropped a bunch of elevation and hit some dry pavement, I coasted down to about 30 and shifted out of 4hi, dash light went out, I got back on the gas and started to accelerate and *POP* BANG* ohF*&k*. I coasted over to the shoulder and stopped. Got out, no visible breakage, had my girlfriend get behind the wheel and creep the truck forward a few feet while I watched. I could see the front driveshaft spinning and heard some un-desirable noises. I turned the hubs to free. Same result. Dejected and tired(it was late) we crawled into our sleeping bags and passed out. In the AM I called for a tow. A shop in Jackson( I had few tools as we had flown out to get the truck) pulled the front driveshaft and gutted the hubs so we could drive home.

Today I stripped the front axle to see what I would find. Halfshafts look fine, splines on both ends look good. Differential is TOAST. Roughly half the teeth on the final drive gear and pinion are smashed off or chewed up. Planetary gears all look ok, bearings all feel fine. I drained the appropriate quantity of fluid from the case, and it was changed in December/ 500mi ago, though it is now black and burnt looking. So now the question is how and why would a front diff on an otherwise solid truck with under 80k on it go out like that? I have a working theory but I'd be very curious to hear what the "locals" here think about it. Thankfully it sounds like the previous owner is going to work with me on this.

So here is my theory; During inspection the PO pointed at the hubs and said "Ive never used those, I just left them in free, it still goes in and out of 4x4 just fine". I guess he didn't really understand what manual hubs do despite being an engineer and an equipment guy. When I heard that I thought, hmmm better cycle those and see if they engage. On my test drive, I did just that and they spun smoothly and seemed to lock in and un-lock though I did not jack up the front axle to really confirm engagement/disengagement. After we concluded our deal we drove at highway speeds for two days straight and made it about 1700 mi before we needed the 4x4 and ended up losing the diff. While attempting to determine what had broken I noted that even with the hubs un-locked and the transfer case in 2hi the front drive shaft was still turning if we moved the truck. The shop in Jackson also confirmed that the hubs were not engaging from the halfshafts. So Failure path in my mind is; Hubs went 15 years without being cycled => I cycled them during inspection => they appeared to unlock however the drivers stayed on the ends of the shafts probably due to corrosion or spring fatigue? => we drove 1700 mi at highway speeds spinning the front diff without noticing => it was nearly cooked and when we used the 4x4 and put some torque to it that was the last straw.


Does this make sense? would spinning the front diff at 65 mph because the hubs were locked really cook it even though it was properly lubricated? Thanks in advance for the input. I of course have many of my own should have/would have lessons learned already here, but welcome yours.
 
IMHO running the front differential at 65 mph (hubs essentially locked) does no harm whatsoever. Any full time 4wd or switchable 2wd/4wd i.e. Unimogs do the same thing. Just burns a bit more fuel.
The PO was an “engineer/equipment guy “? A pretty stupid one!
If ONE hub was locked and one unlocked it would have put tremendous stress on the spiders causing a lot of spinning which might have burned up the oil (viz. “black and burnt “), then power was put to the ring/pinion they broke.
 
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Czechsix

Watching you from a ridge
So in 15 years or so, no maintenance was done to the hubs or bearings?

Previous Owner was an idiot. An educated one, but still an idiot. I'll bet he goes through lots of vehicles.

The one hub theory from charlie is a good one, and I wouldn't be surprised. Alternately, if "maintenance" was done to the wheel bearings, I wouldn't put it past someone to re-assemble the front end wrong, leading to the same result.

The "good" part is now you can drop a limited slip or locker in the front!
 

pugslyyy

Expedition Vehicle Engineer Guy
yeah I'm thinking the same, one hub locked and the other unlocked. I had a hub partially engage on mine once and it chewed up the manual locking hub but that was it.
 

ctane

New member
Thanks for the feedback. Some good points here, esp. about maintenance to the hubs and possible improper assembly.

The PO did say he had the brakes done recently and there is fresh looking looking grease on the spindles. Pads do look recent also to support that. Quite possible the hubs were re-assembled improperly following the brake service. Now I wish it had been me to strip them so I could have noted that.

Yea front locker! I was thinking about that... Trying to find cost. At least we still got some good skiing in along the way.
 

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ctane

New member
Good point Verkstad. This is my first time working inside a Differential. Still trying to learn the names for the different gears. The gears I was referring to would be more accurately called the side gears and differential pinion gears I believe.
 

SkiFreak

Crazy Person
It would be relatively easy for the pinion gears to "lock up".
If any one of the pieces that broke off the crown wheel or drive pinion were to lodge themselves between the pinion gears it would create a physical lock. If this did happen you would probably see damage on the pinion gears too.
More likely, seeing the damage on the crown wheel, is that a piece of broken tooth went between the crown wheel and drive pinion teeth, or the damage resulted in the teeth going completely out of mesh, which would also result in the diff locking up.

Also, if metal bits have been floating around inside the diff, which obviously they have been, I would be changing all of the bearings (no brainer).
Any debris that is floating in the oil will likely pass though ALL of the bearings and cause damage. That damage may not be obvious to the naked eye, or by simply spinning the bearing, but it will be there.

It has been suggested that this might be a good time to upgrade to a LSD/ATB.
That may be true, but be mindful that these diff centres simply replace the pinion gears. You will also need to replace your crown wheel and drive pinion, as they are definitely toast.
Alan is the only person that I know that does a true "locker", but there are a few companies that sell ATB (auto torque biasing) differentials. There are at least 3 that I know of.
Which is better... well, that is personal choice, based on what you intend to do with the truck, but either is significantly better than an open diff. I went with an ATW ATB diff centre, as these are made by Quaife in the UK.
These diff centres will normally run you in excess of AU$2500, depending on the type you get and where you get them from.
 

Aussie Iron

Explorer
It certainly has had some pieces go between the crown wheel and pinion. May be a pinion bearing has collapsed. Little use and a lot of sitting around is good for moister buildup and in the long run bearings don't like that. You would need to do some more exploring into that. If by chance you did run in 4WD on a hard surface tyre wear would be the biggest problem not the diff. One hub partially locked in probably would have wrecked the hub. Just make sure when you start to reassemble that you wash out the axle tubes well as pieces of metal will have worked their way out along them to the outer ends. It would be a pity to do a rebuild and then have to do it again.

Dan.
 

ctane

New member
Thanks again for the input FusoPeople. Aussie Iron, I've been thinking about the axle wash. Seems like its going to be kind of a PITA, trying to decide if I should pull the whole axle or if I could achieve sufficient cleaning with it under the truck.
 

Aussie Iron

Explorer
I'd wash it under the truck even if you used a pressure washer to blast from one end to the other. Then use a rag on a broom stick to dry as much water out that you can and wash down with some petrol to get rid of the rest of the moister. Job done on a nice warm day.

Dan.
 

lanceatm

Founder and CEO of EarthCruiser
In case you don`t already have it. Front axle service info attached.
 

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jhrodd

Adventurer
I've got a spare complete rear axle that you're welcome to have. I don't know how many (if any) of the parts interchange with the front. It's from a 1992 I believe, in really nice shape. In Bellingham, WA
 

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