What problems could half shafts cause? - The Unofficial BMW M5 Messageboard (m5board.com)

911/M5 · 26th September 2002, 20:29

What usually happens to half shafts when they go bad? Is it usually the CV Joints that go out, or can the half shafts actually be bent from engine torque? I have the 18" M-Parallel wheels on my car with 265/35's on the rear. Since my car is a 1991 and built for 16 or 17" rims, I thought there might be a chance that over time the torque from the engine could have put these half shafts in a bind enough times to bend them. Is that possible???

We are still fighting this rear vibration issue. The ONLY things we haven't replaced are half shafts and wheel bearings. Since wheel bearings SHOULD only be a sound rather than a low thundering vibration, we are now focusing on the half shafts.

Any help would be great, as we are all confused... To date parts replaced to get rid of the vibration are: Wheels, rear subrame bushings, engine mounts, shocks, driveshaft, guibo, clutch. The LSD has been inspected and appears to be fine.

Hopefully, someone has some ideas...

bay · 16th July 2007, 13:29

Quote:

Originally Posted by 911/M5

What usually happens to half shafts when they go bad? Is it usually the CV Joints that go out, or can the half shafts actually be bent from engine torque? I have the 18" M-Parallel wheels on my car with 265/35's on the rear. Since my car is a 1991 and built for 16 or 17" rims, I thought there might be a chance that over time the torque from the engine could have put these half shafts in a bind enough times to bend them. Is that possible???

We are still fighting this rear vibration issue. The ONLY things we haven't replaced are half shafts and wheel bearings. Since wheel bearings SHOULD only be a sound rather than a low thundering vibration, we are now focusing on the half shafts.

Any help would be great, as we are all confused... To date parts replaced to get rid of the vibration are: Wheels, rear subrame bushings, engine mounts, shocks, driveshaft, guibo, clutch. The LSD has been inspected and appears to be fine.

Hopefully, someone has some ideas...

Hi

I got the same problem with mine, did you ever find what was the problem ?

farrell · 16th July 2007, 18:40

Hi
Has the car been used for any hard starts or 1/4 miling ?
Any idiot starts undertaken going from slippy muddy surface to grippy tarmac
with wheels spinning ?
Have the half shafts been measured to ensure straightness.
If there is any runout, it should be obvious even using a straight edge of a
steel rule.
How was the LSD inspected ?
Was it just removal of the hypoid rear cover plate to check for teeth missing.
Proper inspection of a LSD & its clutch pack requires its removal from the vehcle.
The System backlash is measured on a rig from input flange to output shaft.
Is it in spec ?
This measurement is taken from the drive & coast faces of the gears &
can be measured in degrees & converted to a more linear dimension.
If load induced wear has occured then its possible the pinion & crownwheel teeth are intermittantly contacting the roots of each other.
There is a probability that certain road speeds are generating a frequency through the driveline parts at the rear of the car coincident with the rotation speed of the driveline parts from the transmission.
This is possibly being excited by the gears bottoming out & causing an low frequency drone with increased perception of noise & vibration.

Drive shafts do fail under extreme use or increased power.
Diffs are usually the first place to vist however.

Farrell

bay · 16th July 2007, 20:57

Quote:

Originally Posted by farrell

Hi
Has the car been used for any hard starts or 1/4 miling ?
Any idiot starts undertaken going from slippy muddy surface to grippy tarmac
with wheels spinning ?
Have the half shafts been measured to ensure straightness.
If there is any runout, it should be obvious even using a straight edge of a
steel rule.
How was the LSD inspected ?
Was it just removal of the hypoid rear cover plate to check for teeth missing.
Proper inspection of a LSD & its clutch pack requires its removal from the vehcle.
The System backlash is measured on a rig from input flange to output shaft.
Is it in spec ?
This measurement is taken from the drive & coast faces of the gears &
can be measured in degrees & converted to a more linear dimension.
If load induced wear has occured then its possible the pinion & crownwheel teeth are intermittantly contacting the roots of each other.
There is a probability that certain road speeds are generating a frequency through the driveline parts at the rear of the car coincident with the rotation speed of the driveline parts from the transmission.
This is possibly being excited by the gears bottoming out & causing an low frequency drone with increased perception of noise & vibration.

Drive shafts do fail under extreme use or increased power.
Diffs are usually the first place to vist however.

Farrell

Hi

I´m the second owner of the car with only 158.000km when I got it. Full service book. Really dont think it´s been used for 1/4miles.
I tried the half shaft from my 93, had 3,23 3,65 and 3,91 LSD on with no difference. Today I tried an second hand driveshaft I got from london mike all the same. I have changes the engine, gearbox and diff mounts new rear wheel bearings, new U-joint and guibo, new pitman arms, powerflew all around, guide support in the rear.
We also tried to drive the car up to 120km/t with out the half shaft´s and your can still fell the vibrations in the seats.
Tomorrow I´ll put another 6 speed box on and see what happens ? dont know what else to tried any more. The funny thing is, when I brake about 120km/t the vibrations gets worse. The rotors are new to with only 0,03 sidecast. If I use the brakes with higher or lower speed it´s all okay.
I really like E34 M5 but right now I´m close to sell it, and go for the E39.

safetywork · 17th July 2007, 06:00

I'm getting something similar.... low speed "growl" or hum. At higher speeds (45 mph) it turns to a vibration. After balancing the wheels, the vibration is gotten significantly better but at higher speeds the vibration returns. But I did notice one of the rear wheels is slightly bent, I'm hoping that's it. I'll be replacing the wheel soon.

Sebring NL · 17th July 2007, 10:28

Quote:

Originally Posted by bay

We also tried to drive the car up to 120km/t with out the half shaft

???

In my experience, big BMW's are prone to vibration.

Like said before, on my 520 E34, we replaced almost anything on the front suspension, and with replacement of the steering rods connecting to the wheel hub it was gone. Only thing was, I replaced only one on monday, because the other one I got was the wrong item ( thread was wrong) so I replaced the other one on wednesday.

problem was back with replacing the second item!!

On E38's, its most often the pitman arm which you say is replaced.

Possibly , its time to have the wheels balanced on the car.

IIRC you have the boat-anchor 345mm disc , so taking all that mass in equation when balancing can never be wrong.

Also, I know a shop in my hometown that could not get rid of these troubles either in an E39. Turned out their tire balancing machine was screwed.

Wout

bay · 17th July 2007, 10:43

Quote:

Originally Posted by Sebring NL

???

In my experience, big BMW's are prone to vibration.

Like said before, on my 520 E34, we replaced almost anything on the front suspension, and with replacement of the steering rods connecting to the wheel hub it was gone. Only thing was, I replaced only one on monday, because the other one I got was the wrong item ( thread was wrong) so I replaced the other one on wednesday.

problem was back with replacing the second item!!

On E38's, its most often the pitman arm which you say is replaced.

Possibly , its time to have the wheels balanced on the car.

IIRC you have the boat-anchor 345mm disc , so taking all that mass in equation when balancing can never be wrong.

Also, I know a shop in my hometown that could not get rid of these troubles either in an E39. Turned out their tire balancing machine was screwed.

Wout

Hi Sebring

Well also tried wheels from my 93 and the old ones from this car. At my work we got 3 Hoffmann machines and 1 Hunter 9700 all the same, at home I got Facom so one of them most be working I hope

Some days ago I even tried the new Xact balance, and absolute no difference

What else can it be, can it be the 6 speed box ? I´ll try another tonight.

Sebring NL · 17th July 2007, 11:56

I'd still try to get them balanced whilst on the car.

That said, thats only when assuming you replaced virtually all the rubbers/joints on the suspension

bay · 17th July 2007, 12:19

Quote:

Originally Posted by Sebring NL

I'd still try to get them balanced whilst on the car.

That said, thats only when assuming you replaced virtually all the rubbers/joints on the suspension

Also did the rear tyres balance on the car, think I did all now but vibrations still there

All rubbers and joints are new, so really dont know what to do now.

I´m desperate so I´ll try the box, even knowing it´s the same.

This morning I was running 120km/t and turned of the engine, still the same so it´s not the duel mass flywheel.

bobz · 17th July 2007, 14:12

I know it might be something you have already done, but have you had the tail shaft checked for runout and balanced?

BobZ