Rear axle problems?

[8erBN]

Something weird happened to my 850i auto 4 speed today. While driving around 40mph, all of a sudden car wont accelerate and there was a loud groin coming somewhat from the rear axle (or rear part of the car) I stopped on the road side and was not able to move the car at all. Tried putting the gears on R and D, it did not move at all and whenever this happens, i can hear the loud groin again. First i thought it was the gearbox, but it seemed to engage in every gear 1,2,3 D and R (although no movement)

So i put the rear on air, tried to put gas on it, saw the left rear wheel spinning and then lay the car back to the ground. Suddenly, everything works as normal again. It was as if the car had no issue at all.

Anyone experienced this before, what problems am i having? I dont feel comfortable driving the car at the momwbt

[rjjablo]

I would be inspecting Brakes, Half shafts and Differential. Unless you can see some evidence of something getting caught around a Half Shaft

[8erBN]

@rjjablo can you explain a little bit more why brakes and half shafts are involved here? I have only thought about the diff so far

[jclausen]

To me it sounds like the brakes locked up, sticking caliper maybe or the rubber brake hose is coming apart internally. You could drain the diff oil and inspect it. The one wheel turning when up means you don't have a limited slip diff.

[8erBN]

What about valve body on the gearbox? Can it cause this kind of problems?

[rjjablo]

What about valve body on the gearbox? Can it cause this kind of problems?

Valve Body could if it failed to engage something

I would pull the tires and do a close inspection of all things in the brakes and half shafts first. Look for "witness marks" of something catching.

Did the rear tires lock up when it did it?

Give all the half shafts a solid tug and look for movement

[Belgiumbarry]

i had sticking brakes .... had to replace the master cilinder. ( '91 850i ) . But also the front ones were sticking. ( and hot discs ! )

[Timm]

Yes, that would be my first guess as well - Master Cylinder slowly applying the brakes!

[8erBN]

I think the rear tires were locked up indeed.i will test the half shaft today and see what happens.

Im surprised that Brake MC can actually cause this issue? Does it program to stop the car fully or something?

[Belgiumbarry]

no, due rust (pitting) inside the bore of the MC , the piston can't fully retract and keeps pressure on the lines … i think.
That's what i have seen on mine : "corrosion" at the front of the bore.

It starts as sticking brakes but can become worse to fully locked due generated heat i suppose.

[8erBN]

I strongly feel that the brakes did not lock up the rear wheels at all now thinking about it because when i put the rear on air and just by shifting the gear to D, i saw the left rear wheel spinning as normal and indeed non LSD.

Im still checking the car at the moment, afraid something is loose causing it not properly engaged

[Belgiumbarry]

yes, but when stopped the pressure go's away after 1...10 minutes and i could drive on. As the time it took to put the rear on air ?
If it happens again , check the temperature of wheels/discs.... with sticking brakes they are really "hot".

[8erBN]

Nothing unusual with the brakes so far, they seem fine.

Here’s a picture of my diff, it has a slight leak on the left halfshaft. I drained the oil for now

FF3C237A-36A3-4B26-9FD8-7B3C73CB8954.jpg
Can it possibly be the gears within the diff itself that is causing all this issue?

[Timm]

It could be the differential - but they get really hot when a bearing starts to fail - and smoke a bit!

[jclausen]

Think about the diff is just to big gears and bearings, other than bearing noise that's the only thing I've seen happen to those, If the mas ther clyinder was sticky I would think both rear wheels would lock up, if it's one side then caliper or hose. If it did it again and you could confirm which wheel was locked unscrewing the brake hose a bit should release pressure and unlock the wheel

[bmw528e11]

I had same thing happen after diff replacement. One of the axles popped out at the differential. Raised up vehicle, and popped it back in haven't happen ever since. Try to pop axle out slightly with pry-bar on the right side at differential. But it takes some patience to pop it back in.

[8erBN]

Thanks guys, im replacing all front and rear brake hose at the moment. Doing it cause i have been having these parts laying around for quite some time. I’ll take a closer look onto the callipers as well (it seems that my right rear wheel was a bit sticky yesterday, starting of with the hose first)

At the same time, im changing the diff oil with 75w 90 (since its an open diff). No noise coming from diff prior to this though.

[8eights]

Put a 3:91 Diff in there, That will fix it.

[TedBobo]

Put a 3:91 Diff in there, That will fix it.

What he said!

[8erBN]

Does anyone know what the diff speed sensor do other than measuring the vehicle speed?

Does it provide input anywhere and can it actually cause the problems im having (like not making the tranny work or something?)

[Timm]

If your speedo works, then it is doing all it needs to do!

[8erBN]

Hey timm, i do have slight delay when accelerating sometimes. Needle couldnt catch up properly. Does the sensor do anything else you know of?

[Timm]

The signal from it is used by a few other systems - it adjusts the radio loudness and wiper pressure/speed - but cars do drive quite happily without any signal from it.....

[8erBN]

Ok thanks mate. I have got the car back on the road for now, replaced the diff oil and all brake hoses with ss (sure felt tighter now). Hopefully nothing weird happens, fingers crossed

[Albert850i]

The car will be bucking like crazy at very low speeds without the speed signal. Error 73.