rattling diff / axle when coasting

Re hubs, most large trucks run oil lubed hubs as they run cooler in general use than greased hubs and require less servicing in the long term/better bearing life.

Grease is more convenient from a car/light truck manufacturers POV. Less leaks, etc and the right grease can be better in extremes, e.g. Extreme hub temps due to extreme brake temps (racing)

Fuel economy benefits from a full synthetic fluid driveline and slightly lower viscosity levels are only in the region of 1.5-2% going off trucking results, a level hard to measure on our vehicles.

Quote:

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Originally Posted by PhilipA

Rick I hear what you say but I found that on a hot day say 32C or more , towing my camper at say 900Kg I started to get noise from the front diff when I exceeded say 120Kmh to run up to a long climb. This to me suggested lubrication failure. I run 80/90 full synthetic in my transfer with an extended sump.

I plan to go to Queensland "shortly" ie when the lockdown ends. I doubt whether the fuel consumption will change much.

It was interesting that the wonka wonka sound only came from the front diff and at high load accelerating with 900kg on the back at 32C plus.

Seeing I plan a Kimberley trip next year I feel the 50/50 mix is justified and cannot do any harm. After all the CVs run grease and in RRCs the hubs went from ep90 to grease.

Regards PhilipA

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A higher visc won't hurt on that trip, but when you're loaded up like that, and particularly going up a hill, there's far more load on the rear diff, and it's copping all the heat from the engine, exhaust and the rest of the driveline, the front diff gets all the lovely cool air.

I like the extra oil capacity with the bigger sump on the t/case, they run hot.
The poor thing cops all the heat from the engine, exhaust, and gearbox.

I started a recent thread on a similar noise on no load deceleration. I included a sound clip. Look it up.
None of the answers were right.
I ended up having a loose cross pin in the rover type diff (IIRC different to the P38 style).
Anyway, it let go offroad and grenaded the rear diff in a quite spectacular way.

To isolate (attempt to make noise disappear), one would need to:
1) Remove rear drive shaft
2) Remove rear axle shafts (or drive flanges)- not sure how P38 is set up in this regard, so ymmv
3) Drive to attempt to replicate fault with Centre diff lock engaged (so you at least get drive!).
...and if noise is gone, rear diffferential centre is the culprit> investigate further.

Thanks for the tip!

We've been in a bit of a pickle here due to all the high water stuff so did not yet get a chance to work on the rangie. It's not that difficult to remove the driveshaft, removing the half shafts though requires me to remove the hub carriers. I'll give it a go since I can check the bearing on the right rear side which is making a suspiciously loud noise.

On a final thought; how would one know if the backlash (which I believe is play from front back?) is too high and what I am hearing is actually gears "clunking" because they are misaligned?

Sorry guys, a complete diff noob when it comes to (re)building them [bigwhistle]

Cheers,
-P

Well,

After a wild goose chase around the car a mate of mine finally laid down flat on the rear lid and stuck his head underneath the car whilst driving and he pinpointed the sound coming from the rear right! Odd how sound sources can sometimes be so hard to find on a rolling car...

Anyway, turns out the rear right bearing was shot. It had very little to no play in it when checking but the outer bearing and race were rusting. The inside was just fine. I have had this happen to me several times now. In fact, the bearings are the only thing that are going on me on this vehicle. I replaced them using a mates 60 tonne press and all should be fine, for now. I have already replaced this bearing once it my ownership of the car so... Perhaps it's not the last time.

Thanks for all the tips!

-P

Quote:

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Originally Posted by prelude

....

Anyway, turns out the rear right bearing was shot. ....

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I would have thought that if it was this RHS bearing, when you turned left, it'd have made the usual grinding/moaning bearing noises.

Though my car is not on the crab when driving ie it does not pull on the wheel, the sound only came to light when I let the vehicle coast and let go of the wheel making the car roll ever so slightly to the left over time and unloading all drivetrain parts. The car had to be on temp and the gearbox oil warm enough to lock up the torque converter and only then when coasting (slowly) would the sound present itself. It's an odd thing right? In any case I am happy I found it :)

Cheers!
-P

Quote:

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Originally Posted by prelude

Though my car is not on the crab when driving ie it does not pull on the wheel, the sound only came to light when I let the vehicle coast and let go of the wheel making the car roll ever so slightly to the left over time and unloading all drivetrain parts. The car had to be on temp and the gearbox oil warm enough to lock up the torque converter and only then when coasting (slowly) would the sound present itself. It's an odd thing right? In any case I am happy I found it :)

Cheers!
-P

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Hmmm.. some weirdy revelations there.

I've had a few autos in my time, at the moment I have to ZF Landrover vehicles, and I've never experienced a transmission where it had to get to temp before the torque converter would lock up.
Obviously you're in the Netherlands, and from what I know you guys get REALLY! .. cold up that way compared to our balmy zeros and one's .. but never had a lockup situation where temp had to be warm.

Wheel bearing wear won't necessarily translate to any alignment issues.

Not long after I got my D1(at the time it had quite new Yokohama AT tyres on it). They made pretty much no noise when new. A few months in and I heard the tell tale of a bearing issue, but thought maybe the tyres began making whirring noises. Tyres noise is always affected by changes in road surface. if you've been to Aus, you will have noticed we have some of the worst road builders in the world(consdiering we are supposedly a wealthy nation! [bighmmm])
I have a drive to work where road surfaces change about 10-15 times in the 30 klm drive, 99% freeway. They resurface a section of road for a klm or two one week, than thats it! The following week they will do .. so the road surface is constantly changing. You can hear the tyres changing their tune with every change.
But a bearing will stay constant .. may sound like mud tyre whining. This is how I noticed it .. so planned to get it done. When I opened it up, turned out that the stub axle was worn just a bit too much for my liking, so closed it back up, even tho the bearing was faulty, and ordered all the parts to do all four corners(completely). Took months for the order to come(from the UK) and I'd put on about 3K klms on that worn bearing. LH front(passenger to us Aussies, Driver to you Euro types [biggrin]). Slowly the mud tyre sounding noise obviously gets worse, so slowing down was the new driving style. Any right turn and the mud terrain like howl was un-bearingable! The the parts came and work got busy so had to delay it so many times .. more klms on the now stuffed bearing. Never pulled either way during this time, only when those Yokohamas lost their air, which they did constantly(or alignment was needed). Nice tyre, but I reckon a bicycle tyre would have been more durable!

Anyhow.. it is good to hear that the issue is settled [thumbsupbig]
But I'd look into why your trans doesn't lock up from cold. From what I understand the P38 uses the ZF HP24 box .. so would work the same as a HP22.
Hopefully not a dying converter, but low oil level will do this too.