ZF 6 speed in my 5.0 S/C.
Gearbox drained and fresh fluid.

The gearbox will now engage in D or R but after a few seconds it will lose drive. I stop, switch off and wait 5 minutes, and drive is restored for a few seconds and then lost again. Rinse and repeat.

I have checked the fluid level. Gearbox sump temperature 32°C via an IR thermometer and engine running; small trickle.

Sometimes, when returning to P from D or R, I hear a springy gear trying to engage sound.

Anyone any ideas? 2010 5.0 SC Autobiography Overfinch in Bentley Silk White pearlescent, 22" Overfinch wheels with 285/35x22 tyres

Quote:

Sometimes, when returning to P from D or R, I hear a springy gear trying to engage sound.

I had my MY12's output shaft splines re-lubricated at 150K kms. The grease was rather dry but the splines weren't worn at all.

RRPhil wrote:

Quote:

Sometimes, when returning to P from D or R, I hear a springy gear trying to engage sound.

This could be your park lock pawl ratcheting against its gear, which implies that the transmission output shaft is still turning when you are selecting Park. This can only happen (assuming the vehicle is stationary) if there’s some kind of disconnect downstream of the transmission e.g. transfer box, propshafts, final drives or driveshafts.
I would raise the vehicle on its suspension and get someone to look underneath to see if they can see a propshaft or driveshaft turning while you are stationary with D or R selected (obviously, for safety’s sake, they need to be to the side of the vehicle and not underneath it).
Another possibility is that the transmission output shaft spline has failed through fretting corrosion due to lack of lubrication.

Phil

Worn-out fine splines will often grip momentarily, possibly before there's much load on the connection.

I got my son to sit in the car, foot on the brake and select D and rev slightly. I could see the front driveshaft, from the transfer box to the front diff spinning. However, the left right driveshafts from the front diff to the front wheels were stationary.

My son then selected rock crawling mode and was able to move the car, presumably where the diffs are locked and it was the rear diff giving drive.

I don't understand why the front diff has failed. I know I refilled it with oil after putting the engine back in. 2010 5.0 SC Autobiography Overfinch in Bentley Silk White pearlescent, 22" Overfinch wheels with 285/35x22 tyres

The stationary shaft may have moved out and disengaged with the splines.

The part number for my diff is LR010798. For availability the 3.6 diesel appears to have the same diff part number, but the 4.4 diesel doesn't. 2010 5.0 SC Autobiography Overfinch in Bentley Silk White pearlescent, 22" Overfinch wheels with 285/35x22 tyres

Dtech wrote:

The stationary shaft may have moved out and disengaged with the splines.

winco wrote:

For availability the 3.6 diesel appears to have the same diff part number, but the 4.4 diesel doesn't.

winco wrote:

Dtech wrote:

The stationary shaft may have moved out and disengaged with the splines.

My part number message crossed with yours.

Thank you. Can you elaborate? By stationary shaft, would that be the pinion onto the crown wheel?

If it has moved out and disengaged, is that terminal, or can it 'be put back'?

Sorry, I am on a fast learning curve. (I have rebuilt a rear diff in a Jeep in the past.)