rambling rollie wrote:

Greetings!

At what point does one do this bearing replacement?
At the "humming" phase? (i almost believe "humming" from FL2 rear diffs is standard)...
Or do you wait until it starts whining? (a significantly higher pitched version of humming).
Or when it starts making "whirring" sounds?
Obviously once it starts making grinding noises it's probably overdue...

I ask because mine has been humming for months (maybe even a year, i cannot remember)....

Before it seizes up, which mine did while driving at 40 MPH, just before Christmas. Although to be fair, mine had no oil in it, so I'm surprised it lasted as long as it did. Hyundai Ioniq 5 Ultimate. The family car.
2009 Rimini Red SE TD4. Gone.
2006 Tonga Green i6 HSE. Gone.
Audi A5 convertible, my daily driver.
1972 Hillman Avenger GT, the project.

MRRover75 wrote:

Hi,

I have given up speculating the main reason why these pinion bearings fail. Only thing I know, is that the 9 ones I have rebuilt, have worked superb and I have no reports back from anyone that they have failed. I guess these has not been on the road long enough to build a greater mileage, but some should have failed allready if something was assembled wrong. I have only used Timken and SKF bearings. Mine has now done aprox. 50000kilometres after assembly, so probably as good as they was when new. Early diffs (-07-09) seem to hold 200000km+ before the pinion bearing fails. later ones more early for some reason but some mentioned that cheap bearing copies from China was used there !?!

Regarding lubrication, there is two oil channels to the outer pinion bearing in the casting. One lower probably below the oil level, and one higher up, probably for ventilation of some kind. Lack of frequent oil changes is probably contributing to a reduced lifetime...


I also feel the pre-load on the bearing seems a bit high, but I have not gambled on reducing this on my rebuilds. Just sticking to the OEM procedure when tightening up. Only thing is that I throw away the torque wrench. A lot more torque is needed to start compressing the collapsible spacer than the specified 250Nm.

Mine actually seized solid while doing 40 MPH just before Christmas, so my diff is now most likely scrap. The cause for this was actually due to there being nothing more than a few drops of oil in it.

I've studied the diff design, and come to the conclusion that these continual failures are probably down to a combination of factors.

The pre-load is I believe too high, for the size of the front bearing used. High pre-load, will result in delamination of the case hardening, which is what appears to happen on these bearings.

This ailment also effects the Discovery 3 front diff, which again is due to excessive pre-load, coupled with too small a bearing for the task. I've rebuilt several D3 front diffs, all suffering the same delamination of the case hardening, and all had excessive pre-load when reassembled using the factory shims, but thankfully its easy corrected before final assembly.

Lubrication, or lack of. Looking at the diff design, the oil feed to the front bearing is poor at best.
All differentials use oil for lubrication and cooling. A standard diff is designed so that oil is freely thrown around all moving parts by centrifugal action of the crown wheel. Almost all differential cases are designed to channel a large proportion of this oil directly to the outer most pinion bearing. See the size of the cast in oil gallery hump in this Freelander 1 rear diff, where the oil travels to the pinion bearing in large quantities.

The pinion is spinning fast by comparison to the crown wheel, so needs a good supply of fresh oil to replace that, oil which is displaced by the bearing rollers.

This is where the flat design of the Freelander 2 diff is lacking, as there's insufficient height for a large oil gallery to capture this centrifuged oil, limiting the oil supply to the front bearing. If the oil supply to a bearing is compromised, then the bearing will run with less than an ideal amount of lubrication, which then causes it wear faster and to run hot. This lack of lubrication, coupled with the higher than I feel is ideal pre-load, is my best guess as to the early and frequent demise of these bearings. Hyundai Ioniq 5 Ultimate. The family car.
2009 Rimini Red SE TD4. Gone.
2006 Tonga Green i6 HSE. Gone.
Audi A5 convertible, my daily driver.
1972 Hillman Avenger GT, the project.