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

[Ben_Vapid]

Brains trust,

D4 8 speed with only 70,000km's. I've had an ongoing issue with a bad rear vibration over 110km's/h. Mechanics have ruled out bearings, driveshaft, wheels, tyres and even handbrake pads. I've just had the gearbox serviced with the pan and fluid replaced. The oil in the pan has a sheen of metal filings and the magnets in the pan had quite a bit of metal as well.

The vibration is just as bad after the service so i'm at my whits end to try work out what's the cause and what to do next. Mechanics have spoken to AB automatics which are apparently well regarded for the ZF's, and they've said this is possibly the torque convertor wearing unevenly. It happens when the transmissions do a lot of short city driving (which is the case for this cars first 40,000) and the TC doesn't always engage or wears unevenly and causes issues like this.

Has anyone had anything like this? Does this sound legitimate or should I be trying something else?

I'm facing somewhere between $7000-$10,000 for a rebuild for what right now feels like a guessing game, so any feedback or first-hand experience would be appreciated.

[justinc]

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

[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

[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

[Eric SDV6SE]

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.

[Ben_Vapid]

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.

[Ben_Vapid]

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.

[Ben_Vapid]

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.

[scarry]

Simple things first,swap tyres front to rear?

[Ben_Vapid]

Simple things first,swap tyres front to rear?

Yup i'm ruling simple stuff out too, swapping for a completely different set of wheels and tyres tomorrow :thumbsup:

[Ben_Vapid]

Update: Issue has vanished right when I was about to do a wheel swap, typical! Mechanic thinks it's the TC just grabbing in a different point and it will come back, but we'll have to wait and see. Got to love intermittent issues :(