Thread: D4 8 speed - Bad harmonic vibration in rear at high speeds.

ANY evidence of metal sheen in the pan or oil, or excessive buildup of fines on the magnets = a transmission problem.

There was a recent thread here regarding fault finding of road noise that turned out to be a delaminated brake pad, however from what you’ve described, sounds like a torque converter. However, as the TC is supposed to lock up at around 1200-1600 rpm (engine speed), I.e in the lower gears, if this is damaged, then the shudder/vibration should be felt at lower speeds as well.

having said that, at 110 kms the engine is doing around 1800-2000rpm, so if not correctly filled or damaged, the tc is not locking up either...

When they did the service, did they fill the transmission to the correct level? The fill level is temperature controlled and the level is correct when fluid dribbles out of the fill hole with the engine idling, transmission oil at 35 deg C and the car sitting level. Did they use ZF lifeguard fluid or a suitable alternative? If not filled correctly, the TC cannot lock up and the transmission may not be able to select the right gear. Running with an underfilled transmission is the fastest way to damage them beyond repair

lastly, for the amount of money you mentioned, I believe you should be getting a new transmission, not a rebuild unit. Agreed there’s a bit of cost involved for the labour to remove and fit.

these transmissions are amazingly strong and also complex, so require a bit of TLC. I hope the above has helped you out with some further fault finding, I’m hoping for you that it’s not a serious transmission issue.

cheers

Bit out of left field but does it have its weights in place at the rear of the vehicle. Not sure in any way whether this would cause what you're describing though. It's just a recollection on my part of the weights being discussed a fair while ago and that if they're not there it can cause issues.

Probably totally wrong but maybe someone can comment whether it is a potential issue or not.

Martin

Good call Martin,

I recall reading that if either one or both of these weights is missing or damaged, the effect is like a wallow or shimmy of the car, as the centre of mass is no longer correct. I could be wrong though, but worth checking out.

Originally Posted by justinc

ANY evidence of metal sheen in the pan or oil, or excessive buildup of fines on the magnets = a transmission problem.

Thanks mate, sounding that way, i'm just trying to navigate whats next.

Originally Posted by Eric SDV6SE

There was a recent thread here regarding fault finding of road noise that turned out to be a delaminated brake pad, however from what you’ve described, sounds like a torque converter. However, as the TC is supposed to lock up at around 1200-1600 rpm (engine speed), I.e in the lower gears, if this is damaged, then the shudder/vibration should be felt at lower speeds as well.

having said that, at 110 kms the engine is doing around 1800-2000rpm, so if not correctly filled or damaged, the tc is not locking up either...

When they did the service, did they fill the transmission to the correct level? The fill level is temperature controlled and the level is correct when fluid dribbles out of the fill hole with the engine idling, transmission oil at 35 deg C and the car sitting level. Did they use ZF lifeguard fluid or a suitable alternative? If not filled correctly, the TC cannot lock up and the transmission may not be able to select the right gear. Running with an underfilled transmission is the fastest way to damage them beyond repair

lastly, for the amount of money you mentioned, I believe you should be getting a new transmission, not a rebuild unit. Agreed there’s a bit of cost involved for the labour to remove and fit.

these transmissions are amazingly strong and also complex, so require a bit of TLC. I hope the above has helped you out with some further fault finding, I’m hoping for you that it’s not a serious transmission issue.

cheers

Thanks Eric,

It's currently not at lower speeds but seems to be slowly coming on sooner. Changing gears or putting into sport mode doesn't change things which seems to help with some other transmission issues so that's what's had me confused.

Yup they used a full transmission kit so i'm assuming it's been filled correctly, this is a reputable LR independent so i'm feeling fairly safe here.

No doubt it needs TLC but i'm pretty stunned i'm in this position after only 70k km's.

Originally Posted by letherm

Bit out of left field but does it have its weights in place at the rear of the vehicle. Not sure in any way whether this would cause what you're describing though. It's just a recollection on my part of the weights being discussed a fair while ago and that if they're not there it can cause issues.

Probably totally wrong but maybe someone can comment whether it is a potential issue or not.

Martin

Thanks Martin,

I assume you don't mean driveshaft weights? We've checked them and they're all still in place. It's going up on the hoist again this week so i'll ask about any other weights.

Simple things first,swap tyres front to rear?