wopfe

I am stuck tried different things but noise stays. The noise/vibration is only there when in any gear, at any rpm between 60 and 80 and pressing the accelerator. No noise when I lift the throttle, no noise when I press the clutch. Any things tot look for?

Tires should shake also when without pressing the accelator i think, fan is not making contact...

slate blue

If I missed it, have you checked the torque tube shaft? That is, is it pressing hard against the flywheel and doing some unauthorised machining your engine block. Check the pinch bolts at the flywheel end. The fact that it only does this in gear under load is saying something.

wopfe

I then need to get the torque tube out right? Thx for the reply!

slate blue

No but you need to undo the flywheel cover plate, you may need to drop the front of the exhaust first. Don't forget to disconnect the battery.

wopfe

Thanks, i will start reading the manuals around that part tonight

wopfe

I got the plate of, but I don't see an obvious problem with the torque tube shaft. Or am I missing something, I was sort of expecting peaces of metal.

It looks like the bearing is a little close to the end of the shaft?

See pictures. Thx!

slate blue

Ok good, can you now undo that hex bolt? Check to see if it is pushing on the flex plate? Then check the thrust bearing by moving the flex plate backwards and forwards. It should hardly move. From memory the clearance should be around 0.40 mm. You may need to lever that thrust plate to get a feel for it. If it is nice and tight great! If not, you better measure exactly what the clearance is with a dial indicator.

Let's hope all is well there, the next area I am suspicious of is the torque convertor bearings. These are at the rear of the torque tube. While the shaft is free from the front mounting, push and pull the shaft, to see if there is much free play. This is not the easiest part to diagnos when it is get starting to play up as the tube bearings can also be crook. Let's see how you go from here. Good luck!

wopfe

I dont think i have a flex plate since i have a manual (sorry never made that clear)...cant reach the hex bolt is there a way of turning the shaft without starting engine etc?

slate blue

Ahh…. I should have asked but most of these noises end up being torque tube related noises. I did say I hadn't had the time to read all the thread My apologies anyway. I did go back and have look through the thread, you fan is certainly well worn and that may just be another job as the other Rennlister noted.

Nothing has been lost, it still may be T/T noise, the easiest way to turn that internal driveshaft is to get a friend to put their foot on the clutch, keep your fingers clear when they do that. Put the box in neutral spin the shaft to undo the bolts.

Before you get to that, the noise is NOT engine speed dependant? It is road speed dependant only? Or engine load dependant? Or a combination of some or all? It may pay to try and diagnose these better before doing more of the pulling apart.

I think you are right to raise your suspicions regarding the torque tube bearing location. Yes they can move, the tube gets oil and sludge in it and the bearing carriers deteriorate and move around. Normally there is 2 bearings, these are located normally closer to the centre of the tube than yours as the rear coupling supports the shaft as does the front bearing in the flywheel. Maybe if the centre of the shaft is not supported it is suffering some vibrational resonance is occurring.

Can you support the car on stands and run the car in gear and listen to the drivetrain more closely? Let me know if you need more specific advice.

Schocki

Since the problem is only speed related and load related I would eliminate the torque tube out of the problem area.
I would do two things now:
1. Swap the front tires to the rear and vice versa (according to your avatar they should be the same)
If the problem goes away...well done!
2. If the problem stays: swap the CV joints around and reverse their direction of rotation

Just my angle of attack to resolve the issue.... Hasta luego ...

wopfe

Hi there,

Thanks again both Slate blue and Schocki for keep giving suggestions!

1. It is not engine speed dependent, I can drive at any speed or RPM lower then 60mph, full throttle, half throttle doesn't matter -> no noise, no problem.

2. When I am getting near 60 in any gear at any engine speed, you can start feeling/hearing the grinding, almost knocking noise when I press the accelerator.

3. When I then lift the accelerator peddle, the noise is instantly gone. I can even rev the engine while pressing the clutch no noise. I can do that at 60, 70 or 80 MPH doesn't matter, lift the accelerator and noise is gone.

I think that is why it isn't a tire problem, I would expect to keep the noise when pressing the clutch.
It feels like engine load related, it could be that around 60, accelarating takes more engine load then in lower speeds.

Maybe the CV joints start having a problem when turning at 60 or higher and with load? I might try Schocki's swap trick? Even tough not sure why that would help?

Schocki

If the CV joints are worn and you swap them around you would use another (not so worn) spot on the cages and bearing *****. It is a comon trick in the 944 to extend the life of them. The swap is easy in the 944 because the are onle bolted with allan bolts. In the 928 you need a little more "uuumpf", the central bolt at the tires requires a little more torque. After that bolt it is a walk in the park...

9x8

Early 928's are like 944's, outer CV joints are also bolted on from the inside.

wopfe

Ok i got the solution. Or actually solutions...i cleaned, and refilled my CV joints with grease. After that i swapped the axles from left to right. Then i got my wheels balanced right after that...stupid enough i didn't drive faster then 60 mph, only after the balance...good news was i lost the grinding sound, but what eventually solved it was unclear...do both if you encounter the same problem and i guess try the wheel balance first... Thanks again for the suggestions!