Front Diff Failure (FDF)

[Bounder]

There is two taper rollers in the pinion the rear one is fine, the front one, closest to the ring gear was completely dry and failed.
The two tapered rollers that support the halfshafts were fine as well.
It seems to drive fine with no shafts in the front hubs, should be OK hopefully.

 

[Chas]

Chas - is that your right click or our right click? Right hand is the one you scratch your bum with - yes? Chris

Depends which side the itch is on, but it's the same one I pick my nose with, does that count?

 

[Chris]

Well with no prop and no half-shafts, the diff isn't doing anything, of course. But what I wasn't sure about was what would happen at the hubs. Presumably the shafts don't hold the wheel bearings in then? I never removed a hub on on 90 so never had a look inside. So did you put the casing back in then?

Incidentally, did you have to take the companion flange off to get it over the cross member? I wasted 45 mins trying to find an angle and in the end unbolted it.

Chris

More pics would be really good on this one!

 

[Bounder]

I took the companion flange off as per your advice, the nut was only loosely staked on and it took very little pressure to remove it.
No casing or anything just a void where it used to sit.
I think bob murphy posted that it took between 25 and 50t pressure to get the bearings out of the hubs, they are only an interference fit so I really don't want to be doing any road with it the way it is, but at least it's mobile.
I think I was lucky, a locked front diff could have been a very nasty situation at speed
Seals and clips ordered now so hopefully they will be here Monday and I can stick the new old diff in then.

 

[BobMurphy]

The drive shaft doesn't hold the front hub on. It can't if the shaft is just held into the diff by a snap ring.

The hub is pressed into the bearing assembly (I'm told it takes about 3 tons to fit a new one, about 25 tons to shift an old one ).

The Hub + bearing is pressed into the steering knuckle and the bearing is retained by a snap ring.

I haven't stripped a front hub myself, but I can't see anything holding the hub in the bearing, which is a bit worrying - unless there is a lock nut on the back - shown here as "Free Wheel Hub Lock Nut/Spacer":

I can't believe its all held together just by pressing the parts together.


Someone will know the truth . . .


Bob.

 

[Bounder]

Update.
I now have a replacement diff, R16 code which means 4.100. R17 is the code for 4.300.
There is a little rectangular sticker on the extension tube on the drivers side that has the code on and date of manufacture.
Funnily enough it came off an Import Prado 95 Auto.
I am not going to stick it in until there is fresh seals and clips for the halfshafts, I think the seals are possibly easier done off then mounted.
You find lots of stuff in breakers yards, the guy offered me the intercooler and multigauges and electric aerial for another 100 , How could I refuse?

 

[Steve H]

There is a machined lip inside the steering knuckle which you press the new bearing up to and then fit a locking snap ring in behind it to hold it all in place. You then press the axle hub into the bearing after fitting the oil seal against the lip holding the bearing. The rear oil seal goes in and the drive shaft goes through the axle hub held in place by the locknut. I think I had the press up to 15tons to get the old one out and 3 to 5 tons to press the new one in. Did it a while ago now but I'm sure I posted it on t'other forum. HTH

 

[Bounder]

That makes perfect sense, so the hub is held on by the driveshaft which butts up against the back of the knuckle, the 35mm locknut provides the clamping force.
I suppose it's best not to be doing too much driving on it then without the shafts in place.

 

[Steve H]

The hub is press fit into the bearing so has to be pressed out as well as the bearing. But driving around without the driveshaft holding it all together is not something I would do personally. By the way , Bounder, did you get the inlet manifold and throttle body with that intercooler? The manifold on the non cooler engine is sloped to mate up with the crossover pipe. You will also need a longer throttle cable to reach round the intercooler to the throttle. You will also need to reroute your auto box kick down cable to come up to the throttle as well. I have all the bits to do this in my shed, just haven't fitted it yet.

PS Sorry if this is a thread hijack. Didn't mean to do it

 

[Bounder]

No worries Steve, I am not driving the truck around, I just wanted to be able to move it up onto some ramps so I can work on it without getting soaked.
I haven't picked up any of the kit yet, but I understand the intake manifold is different from the non cooled version.
throttle cable is also a seperate part# as well.
There doesn't appear to be any temperature sensors or any electrical stuff at all with the I/C?
Mine is a manual so I don't have to route the kickdown cable either.
I might take a few pics of the process as I go, but it will be after the diff gets fitted!
Not looking forward to fitting it on my own, its a heavy lump.

 

[Bounder]

Update:
I fitted the diff yesterday evening, took me about 4 hrs in total including fitting new seals to the diff, they are relatively cheap at €37 for the two and 4 spring clips
New seals are the rubber coated type the old ones were bare steel with a rubber lip.
I knocked them in using the old seals as I had nothing that size as a drift.
My arms are a bit sore today from benchpressing the diff several times in order to refit it.
If you do this, remove the companion flange before attempting to remove or refit the diff, on a manual the pipework for the clutch gets in the way.
Not a big job to take it off there is a 24mm nut lightly staked to the shaft holding it on.
The diff only holds 1.2 litres of 80w-90 so I am going to replace this more often, given that the split is 50/50 front rear the oil is going to be under more pressure than the 2.6l in the rear diff.
Personally I think a lot of the failures will be because of seal failure and oil breakdown.
The input shaft has two taper roller bearings and the front one has more stress on it as the load is off centre when the pinion is driving the ring gear, any wear here will probably make the gear meshing a bit haphazard and could lead to tooth chipping or similar.
My own diff failure was down to not spotting the oil seal failure in time, but given the relatively low oil capacity it can leak away quite quickly before you realise, especially doing motorway speeds.
More frequent diff oil changes would have spotted it before it caused trouble.
Top tip to remove the old seals