MAN LE150C brake or transmission problem?

UK PROFESSIONAL DRIVERS FORUMS OWNER AND FLEET OPERATORS FORUM (INTERACTIVE)
1

2002 LE150C 8 tonne box van plated 7.5 tonne for the UK. Just under 500,000km indicated.

Nearly a year since my last post, the old truck’s not doing too badly but I’m starting to wonder if I shouldn’t be posting in the Old Timers section. :slight_smile:

In August 2015 I took the truck down to the south of France and back.
On the way south the truck was fully loaded, on the way back north it was more or less empty.
Most of the journey was on motorways, mostly at about 50mph. The truck is limited to 56mph.
It was very hot in the south, sometimes touching 40C in the daytime. I’ve never driven this truck in those temperatures before.

Heading south (loaded), some way south of Orleans, I noticed a sort of juddering, a bit like going over a rumble strip. It seemed to shake the whole truck.
It eased when I slowed down, but gradually it got worse until no amount of slowing down would ease it.
I pulled off the motorway at a services to investigate.

Near the rear axle I saw that a narrow hose connected to the differential housing had spewed gear oil all over the back of the chassis. I concluded that the oil must have all gone and the differential was probably toast, but after checking the oil level in the diff I breathed a huge sigh of relief because it was pretty much where it was when I left England. I guess the hose is just a breather to vent oil as it expands at high temperatures.

After letting it all cool down for a few hours I continued the journey and the juddering had gone.
But it came back again after some more hours at 50mph, and now it seems to do the same thing any time I run at that sort of speed for anything like an hour - even with no load.

If I stay below about 45mph it doesn’t seem to develop the problem at all.

I can’t decided if the juddering is going at wheel speed or prop shaft speed. If anyone has any ideas about that I’ll be please to hear them.

The prop shaft bearings are all sealed things, no grease ■■■■■■■ anywhere. At one stage I’d almost convinced myself that the problem lies in the bearing housed in the differential case at the aft end of the prop shaft, but I don’t have good evidence for the theory. It seemed to squeak when I rocked the prop shaft a few degrees back and forth but it’s difficult to know where the squeaks come from. I see no way to lubricate it. I now think that if it was a bearing it would have failed completely before I got back to England.

I’m wondering if maybe there’s a siezed piston in a caliper or something like that.

Before I start stripping calipers and things, any thoughts?

2

Could be diff bearings ,they’re not brilliant on those models ,member 1970 commer has had his fair share with them .

3

As already mentioned sounds like an overheating bearing as even in hot climates I wouldn’t think it would be enough to heat the diff oil to a temperature to force it out the breather unless something was awry.

Bearings can grumble on for a long time.

Can’t see that a stuck caliper could heat the axle casing enough to force the oil out the breather either, the tyre would explode or wheel catch fire long before.

4

Thanks for the replies guys, I’ve PM’d 1970commer to see if he can offer any tips.

Are MAN differential bearings generally easy to replace?

5

Not and do the job properly.

6

cav551:
Not and do the job properly.

Could you expand on that a bit?

7

I’ve had a couple of diffs go over the years in 10 ton gross MAN’s but it has been the spline on the end of the halfshaft wearing until it turns in the diff and you lose drive, the best way to approach this problem is take the diff to H.L. Smith and have them recondition it, my last one cost just under £800 + VAT.

Reading your account of the problem though I would be inclined to have a good look round the tyres first for any deviations in the tread or bulges that develop when they become warm, after that jack each back wheel up and turn it by hand, if there is anything amiss to cause the problem in the diff you should be able to hear it, if you drain the diff oil you should get a good idea if there are any problems in there by the colour and texture of it, if it is a metallic colour with shiny bits in you could have found your problem.

8

Thanks for the reply, I’ll do what you suggest and report what I find. It might take a while.

9

ged:

cav551:
Not and do the job properly.

Could you expand on that a bit?

You will not be able to inspect the bearings properly without removing the diff and stripping it down. Reassembly and setting it up is a skilled job which many fitters these days would not dream of attempting, mainly because it has probably been years since they last did it. I appreciate the vehicle is an old nail so cheapness is the word and the diff is probably not in the best of health anyway. You might be lucky and manage to replace the outer pinion bearing on its own with the diff still in the axle, but you won’t know what the others are like nor will you be able to set up the meshing, preload and backlash.

By all means take the lot out if everything points to the diff, but a scrap yard diff is probably the way to go from there.

Drain the oil and see what comes out, anything bigger than a little-fingernail clipping is certainly trouble.

10

cav551:

ged:

cav551:
Not and do the job properly.

Could you expand on that a bit?

You will not be able to inspect the bearings properly […] you won’t know what the others are like nor will you be able to set up the meshing, preload and backlash.

By all means take the lot out if everything points to the diff, but a scrap yard diff is probably the way to go from there.

Drain the oil and see what comes out, anything bigger than a little-fingernail clipping is certainly trouble.

That’s very helpful, thanks very much. I’ve never done such a job and from what you say it sounds like I’m never going to. As you say, a scrapyard might be the logical answer if it turns out to be a problem with the diff. I’ll certainly now be draining the oil just to see what’s in there, and your description of what to look for is very helpful to someone like me who has absolutely no basic information to work from. When I looked at the oil at the motorway services in France it looked pretty clean, but I haven’t taken a sample, nor dug around in the bottom of the casing to look for bits of broken teeth. I guess doing those things will tell me much of what I need to know. I’m keeping my fingers crossed now!

Thanks once again for the help.

11

Why not treat yourself to a digital laser temperature gun, £10 off eBay, and you can zap everything after a run and see if anythings hot?

12

Mattwoodtransport:
Why not treat yourself to a digital laser temperature gun, £10 off eBay, and you can zap everything after a run and see if anythings hot?

Not a bad idea, although everything seems to be hot after a long run.

When I first noticed this problem, I called my MAN dealer and asked them if it was normal for the wheel bearings to get hot.
They told me that, on a long run, it’s normal for them to get too hot to touch.

Until this issue I’d never noticed the wheel bearings getting hot.
The front bearings don’t seem to, but the rear bearings definitely do - almost too hot to touch on a long run.

When I first stopped to investigate this rumbling issue in the south of France, the entire differential box was almost as hot as the wheel bearings.
On the other hand, so was my mobile 'phone, and that was in the cab!

As not quite a side issue, do these kinds of operating temperatures for bearings and the diff sound reasonable to people here?