Engine: TDI: Droning sound and vibration in accelerator pedal

[miccurr]

Hi lads, i have a 98v70tdi, after fitting new tyres on the front I’ve noticed a loud road noise. This has gotten progressively worse. I’ve swapped the rears and no change. Wheel bearings seem fine. All engine mounts are new, timing belt and pump timing belt are new, engine is in time. I’ve put the car on the lift and taken it up to 1500 revs in second gear and there does seem to be a vibration as if a bearing is shot. The gear box was taken out 14months ago to replace a bearing in it. The condition my car was returned to me gives me no faith in the quality of this work. Any ideas? The droning sound doesn’t disappear if I dip the clutch and I feel vibration in the accelerator pedal even though this is fly by wire. I would take it to a mechanic but because the times we are in I don’t know when this would be possible. 248k on the clock. This car wants for nothing anything it needs it gets.

[miccurr]

After checking everything, decided it’s the gearbox, anyone have one in Ireland or around Lancaster? 5 speed manual for d5252t. Seen one on eBay but it’s collection only.

[martin_r_smith]

Are you sure the mounts haven't gone soft allowing the gearbox to sit and vibrate on the subframe?

[miccurr]

Nope, mounts are new and gearbox is clear of the subframe

[pyro]

Hi Miccurr,

Fellow v70 2.5d owner here! (with its own issues!)

Couple of things that I've noted that make a huge difference to how the car drives:

I noticed a lot of road noise when I had a new set of tyres fitted, - new spring tops and bearings made a huge difference and then checking/adjusting the camber angle/tracking afterwards

The dynamic timing makes a massive difference to noise and vibration too, along with cold starts, power, smoke etc.

The engine mount under the crank pulley can cause some perculiar things, for me, excess noise and vibration, perculiar steering.

Have you investigated the crank pulley/damper, iirc volvo is no longer available, however vw still produce it. I've no experience of one failing, just a thought!

If the vibration is still present when you dip the clutch, what makes you think its the Gbox?

Cheers

-pyro-

[miccurr]

Hi pyro, the crank pulley originally was the beginning of my problems, the original had deteriorated with age so it was replaced, but without the diamond coated washer and quite possibly not tightened to the correct torque. This resulted in a bit of play which eventually led to damage of the mating surface of the pulley, a worn key way on the timing belt gear and a bearing in the gearbox. So, new gear from vw heritage parts, aftermarket crank pulley and new diamond washer along with timing belt kit. New engine mount under the crank pulley which had totally collapsed, new top mount bushing, new gearbox mount. Vibration is only evident when accelerating in 3rd and 4th gears, no vibration when clutch dip but drone is there. Wheel bearings are good, left replaced last year and right replaced a year before that. Engine sweet as a nut when reving. Pump timing spot on, tracking spot on. Originally thought it was the new tyres but that was coincidence as it has gotten progressively worse. Top shock mounts were done within the last four years along with new shocks.
Expecting delivery of what I’m told is a good gearbox with low miles this week, so once I’ve swapped it out, hopefully problem will be solved. Talked to a gearbox specialist and he seemed to think it was the gearbox. A used unit seemed better value especially since someone was in the gearbox already and the casing had been damaged and is missing a bolt.