Rear Diff, should I be worried?

[monkie]

I'm celebrating Easter by changing all the oils on my 110. Dropped the oil from the rear diff and noticed a number of brass flecks in the oil. Is this serious? 

 

[Hybrid_From_Hell]

Hmmm

 

Whats the diff itself, as majority don't have anything brass in them ?

[Snagger]

Sure it's brass?  I think it's more likely bits of steel with a film of oil giving a brass colour.  You'll know for sure if you sweep a magnet through the oil.

[monkie]

Thanks chaps, that's interesting. They sure looked like brass to me but it might just be the morning sunlight playing tricks with me. I'll sweep a magnet through. 

[monkie]

Yes it is bits of steel sticking to a magnet. It was only present in the rear diff. The oil was otherwise quite clean with no water contamination. Is this just normal wear and tear or is my diff wearing out? 

[Snagger]

I'd say it's normal, but Nige would know better!  Get some of his magnetic drain plugs and monitor them.  I replace transmission oil every 10,000 miles - I think the schedule is 12,000, but most people overlook it and only ever top-up, not replace it.  If you haven't replaced the oil in  along time, then this amount of chips/filings is almost certainly not indicative of a problem.

[monkie]

Thank you. I last replaced the rear diff oil 2 years ago. I don't recall seeing the metal flecks in it. I think I will drop the oil again in 6 months time and get one of those magnetic plugs. The front diff was fine.

[Snagger]

If there is an increase in material being lost, then I'd expect it to be a bearing going bad, not the gears, so keep a listen out for howling or grumbling.  At least it's a cheap(ish) fix.

[monkie]

On 4/22/2019 at 7:58 AM, Snagger said:

If there is an increase in material being lost, then I'd expect it to be a bearing going bad, not the gears, so keep a listen out for howling or grumbling.  At least it's a cheap(ish) fix.

I've drained the diff today. 6 months of use and a few thousand miles. There are flecks in the oil. There is no rumbling noise or whining. Do you think it is likely a bearing on its way out? 

 

[Snagger]

I don’t think that’s normal from a diff,  it stand to be corrected.  I’m used to seeing grey oil from diffs, but not flecks.  If it’s not noisy, I still suspect bearings before gears, but you being a 90 owner, and my short experience with a late 90, I’d also be highly suspicious of the cross-pin and the carrier hole in which it sits.  The hole had elongated enough on my wife’s 90 to keep shearing the roll pin securing the cross-pin, so the cross pin slid out and was only retained by the ring gear and hit the flat of the pinion head each full rotation.  You may have some pin or carrier wear, though if you have the cross pin with circling, at least they don’t tend slide free.

[monkie]

1 hour ago, Snagger said:

I don’t think that’s normal from a diff,  it stand to be corrected.  I’m used to seeing grey oil from diffs, but not flecks.  If it’s not noisy, I still suspect bearings before gears, but you being a 90 owner, and my short experience with a late 90, I’d also be highly suspicious of the cross-pin and the carrier hole in which it sits.  The hole had elongated enough on my wife’s 90 to keep shearing the roll pin securing the cross-pin, so the cross pin slid out and was only retained by the ring gear and hit the flat of the pinion head each full rotation.  You may have some pin or carrier wear, though if you have the cross pin with circling, at least they don’t tend slide free.

Thank you. I agree that this certainly doesn't look normal. The oil was otherwise okay and still had a golden colour. I must have a blocked breather as there was a hiss when I undid the filler plug before draining. 

This is a Salisbury type diff on my 110. I don't know what the internal differences are between that and the rear diff on a 90.

[FridgeFreezer]

Just to say, magnetic drain plugs are your friend - and Nige sells some fearsomely strong ones.

[Snagger]

I’d pull the diff to check all the bearings.  People are scared of the Salisbury, but it’s easier to do this job than on a Rover in most respects - it just takes a bit of physical effort.

 

Drain it, remove the prop and mark the pinion nut and pinion before undoing the nut.  Having someone stand on the brake pedal may help, but the best way to stop the pinion rotating is to fit two old bolts through the flange and use a sturdy bar across them to the ground.  Then pull the half shafts.p and diff bearing caps (mark them for side and orientation first).

Ideally, you’d use a spreader tool to make diff removal easier, but you can get by without it - you just need two bars to pry the diff back evenly and square.  Be careful - it’s heavy and may jump as it clears the last of the binding in the bearings.  Good to have something soft under the axle for it to fall on, just in case, and I don’t mean your face or chest!

Once it’s out, you can check the bearings.  You’ll be able to check the rear pinion bearing (nearest the gear), but to check the smaller front bearing, you’ll need to remove the pinion seal.

As long as you replace the bearings with decent quality new ones of the same bearing number, then you don’t need to worry about setting things up when you reassemble it.  Just reuse the original shims exactly as they were and it’ll be perfect.  They won’t drop out and get mixed up - the pinion shims are trapped between the rear bearing outer race and diff housing, while the centre’s shims are between the centre and its inner races on each side.

You'll need a bearing puller to remove the inner races from the centre and rear of the pinion.

You may find after all of that the bearings are ok, but at least you’ll know.  In that case, the only part you’ll need is a new pinion seal (and pan gasket, unless you prefer RTV sealant).

It will also give you the chance to check the ring and pinion gears themselves to chips or odd wear patterns.  Checking the planet and side gears is a bit more involved, but probably easy enough.

The other plausible source is the shaft splines, but I assume you’ve already checked them.

[monkie]

Thank you Snagger for that comprehensive description. I haven't actually checked the rear splines for wear, only the front when I replaced the swivel housings. All was in order on the front but then again I don't have metal flecks in the front.

The alarming thing is that quantity of flecks collected in 6 months was of a similar quantity to that I noticed when I changed the oil in April. That had been in a couple of years. 

I will also be buying some magnetic plugs for the engine, diffs and gearbox/transfer box from Nige. 

I will carry out the work you describe and inspect the rear diff components carefully. I think trailer fitter has some videos on youtube. 

Thank you again for the help, well worth the monthly donation to the forum 👍

[Bowie69]

To be honest, the flecks in that oil don't look like bearing material, more like chunks of crownwheel/pinion.

Bearing material from roller bearings tend to be finer unless they are about to fall to bits.

I'd certainly be removing the cover and taking a visual look, it is one of the benefits of the Salisbury over Rover type axle.

[monkie]

8 hours ago, Bowie69 said:

To be honest, the flecks in that oil don't look like bearing material, more like chunks of crownwheel/pinion.

Bearing material from roller bearings tend to be finer unless they are about to fall to bits.

I'd certainly be removing the cover and taking a visual look, it is one of the benefits of the Salisbury over Rover type axle.

What could be the cause of the crownwheel/pinion to be disintegrating like this? The oil was otherwise okay with no water contamination or other material. Its a good tip though. I will be draining and taking the cover off to inspect. There is quite a clunk when I take up drive from a start. 

[Bowie69]

Just end of life wear, or perhaps a bearing IS gone, but it is just allowing the pinion to smash into the crownwheel every time you pedal it...

[lo-fi]

As a point of reference, this was still (miraculously) driving fine despite the front pinion bearing having totally collapsed:

https://youtu.be/8RyXD-9V9nU

 

 

 

 

 

If you look carefully, you'll see bits of smashed up roller in the stinking, oily mud

 

It's a Rover type, but you get the idea.

It was from a bodged five speed into 88" install where the rear prop ended up about 6" long, and had been heavily off-roaded with seemingly zero maintenance. I expect your clonk may be some accumulated wear in something, meaning the mesh isn't right and the gears are suffering. Quick job to pop the cover off on a salisbury and take a peek. A healthy one has about a degree or two of play between the tooth mesh back and forth on the pinion. 

 

 

 

Edited October 21, 2019 by lo-fi

[monkie]

Thanks for the interesting pictures and video clip. I am now intrigued to take the cover off my diff and have a look. The small glimps of the crown wheel I got through the filler plug showed it to be nice and clean and not covered in think messy gunge. 

[lo-fi]

No worries

I expect yours to be clean inside, it was more to illustrate how bad a diff can get and still drive. That one has been habitually bathed in mud with failed seals, so it was only going to end badly. 

I have a few series Salisburys in the back of the garage, one with far too much play in the gear mesh. I've never had it apart to investigate why though, so I'll be interested to see what you find. 

[monkie]

Yikes, I've just seen the cost of rear diff parts. I'm hoping it's a bearing! 

[monkie]

On 10/21/2019 at 4:03 AM, Snagger said:

Ideally, you’d use a spreader tool to make diff removal easier, but you can get by without it - you just need two bars to pry the diff back evenly and square.  Be careful - it’s heavy and may jump as it clears the last of the binding in the bearings.  Good to have something soft under the axle for it to fall on, just in case, and I don’t mean your face or chest!

I've been looking at what's involved, I'm not entirely sure I understand the function of the diff spreader. Does it pull the final drive unit out of the housing? 

[Bowie69]

It stretches the diff casing slightly so the diff can be pulled out more easily.

Without it you are into lever bars to remove, and large fubber mallet to reinstall, but perfectly doable.

[monkie]

I see. Thank you. Anyone got one I can borrow or is it just as easy with lever bars and a big mallet as you suggest? 

[Bowie69]

Most diyers get away with levers and a big hammer