Can anyone confirm if the gearbox will slip out of gear when going down a hill (and revs go own to about 750rpm as if idling) by design or is there something wrong with mine?

I live at the top of a long hill and noticed yesterday the car was picking up speed on the decline instead of from what i remember a steady speed controlled by engine breaking. Only noticed it yesterday and of course this morning.

RR ownership has turned me into a nervous wreck waiting for something major to go wrong

Cheers,

Pete. L494 3.0L SDV6 Autobiography in Chile Red (Current)
L320 3.0L SDV6 Autobiography in Baltic Blue (RIP 29/03/2021 insurance total loss)

No, it shouldn't do this. It should stay in gear and hold you back if it's in a low enough gear. If you apply the brakes, it will sense you want to maintain a steady speed or slow down and the gearbox will change down accordingly. Kev

MY2014 L405 RR Vogue SE 4.4 SDV8 in Corris Grey
MY2010 L320 RRS HSE 3.0 TDV6 in Stornoway Grey

Great

I also get a shunt when coming to a stop as per this thread https://www.rrsport.co.uk/forum/topic56591.html wonder if its related? It started exactly the same time i had a mega flush and reset from a reputable and known Indy.

Any speculation would be appreciated.

Cheers,

Pete. L494 3.0L SDV6 Autobiography in Chile Red (Current)
L320 3.0L SDV6 Autobiography in Baltic Blue (RIP 29/03/2021 insurance total loss)

manually select a lower gear and see if its ok.

I'll try manually changing gear later however Its as if the car slips into neutral on its own though so appears not to be in a gear. The revs drop to the resting idle speed of 750rpm coasting at 35mph in D. Even coasting in neutral the revs would normally be at 1100rpm ish? L494 3.0L SDV6 Autobiography in Chile Red (Current)
L320 3.0L SDV6 Autobiography in Baltic Blue (RIP 29/03/2021 insurance total loss)

That is weird, Pete. Try lightly braking as you are going down the hill to see if it changes down. Kev

MY2014 L405 RR Vogue SE 4.4 SDV8 in Corris Grey
MY2010 L320 RRS HSE 3.0 TDV6 in Stornoway Grey

knwatkins wrote:

That is weird, Pete. Try lightly braking as you are going down the hill to see if it changes down.

Kev

At all times, or only when cold?

Only cold it seems, just gone up and down the same hill twice to try to duplicate.

Wonder I’d there’s a mechanism doing it to not put too much of a load on a cold engine? L494 3.0L SDV6 Autobiography in Chile Red (Current)
L320 3.0L SDV6 Autobiography in Baltic Blue (RIP 29/03/2021 insurance total loss)

Thats normal. The TC doesn't lock when the temperature of the oil is below a preset value

I love this place, you guys are awesome

Worrying thing for me, my local 'specialist' suggest i take it round tomorrow for them to have a look at, why doesn't he know?!  L494 3.0L SDV6 Autobiography in Chile Red (Current)
L320 3.0L SDV6 Autobiography in Baltic Blue (RIP 29/03/2021 insurance total loss)

I thought the box hangs on to the lower gears until the fluid has warmed up, Mike? (ie. to warm it up quicker)

Or is that a different characteristic to what Pete is experiencing? Kev

MY2014 L405 RR Vogue SE 4.4 SDV8 in Corris Grey
MY2010 L320 RRS HSE 3.0 TDV6 in Stornoway Grey

To an extent

I'll disregard the 8HP box, as it will lock the TC at much lower temperatures, and is a much better gearbox in general

When cold, the TC does not lock so the engine does not become bogged down in low gears. This is most noticeable when you pull out of a junction, the engine just seems to rev, as the TC is open. When the box is hot, the TC can be regulated to allow a degree of slip, for improved acceleration at slow speeds, and then fully locked for max efficiency

The same happens while slowing down. Because the TC is not locked, the engine speed drops back to idle, and there is very little engine braking. When warm, the TC stays locked, and gives the engine braking effect

Ah, I see. Thanks, as always, for the explanation  Kev

MY2014 L405 RR Vogue SE 4.4 SDV8 in Corris Grey
MY2010 L320 RRS HSE 3.0 TDV6 in Stornoway Grey

knwatkins wrote:

I thought the box hangs on to the lower gears until the fluid has warmed up, Mike? (ie. to warm it up quicker)

Or is that a different characteristic to what Pete is experiencing?

Mine seems to do this on occasions when cold, I sometimes wonder if one day it won’t change up  Steve

2005 2.7 TDV6 HSE, ongoing project.
1998 Volvo V70 R auto FWD, mothballed future project.
1999 BMW Z3 (owned from new) garage queen.