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[Ian_D]

I know some automatic gearboxes can be damaged by doing so.

What about the Omega's gearbox?  :-?

[sassanach]

please enlighten,how can you damage a gearbox in "park" by revving the engine? :-?

[tunnie]

in Park I thought the torque converter is not engaged? So revving it, would be harmless?

[tidla]

revving it in neutral and slamming it in drive maybe?

[Ian_D]

This was the post which I read about it - yes I know this is a BMW forum, so totally different gearbox etc...

http://www.bimmernut.com/forum/5-series-bmw/42394-revving-engine-nuetral-bad.html#post331405

I've also seen a fair few autos that lower the rev limiter to around 4k when in P/N?

[TheBoy]

I guess the ATF could get hot  :-/

[the alarming man]

The boy has got it right...well on a volvo anyway...the newer boxes are fine but anything from a 740 upwards it is big no..no...and it is because the ATF can not be cooled quick enough ....anyway why would you want to rev whilst parked considering the price of fuel these days  :-?

[Kevin Wood]

in Park I thought the torque converter is not engaged? So revving it, would be harmless?

Torque converter is bolted to the back of the crank so it's always engaged.

I can't see a problem. Bits on the input side of the gearbox will be spinning, just as they are when you're driving, but with no load.

Banging it into gear at high revs would clearly be a bad move, which is probably why some cars apply a lower rev limit out of gear. :-/

Kevin

[Marks DTM Calib]

thinking of the auto box design, its difficult to see how it could cause an issue.

[Lizzie_Zoom]

.............and in the article about an auto box clutch plates being burnt out is mentioned!!

Somebody's on something here!  Never had a problem in high revving my auto's in park!

[aaronjb]

From TFA:

The problem is that after starting the engine, and selecting any gear, forward or reverse, the front clutch pack in the transmission is pressurized, and that pressure is not bled off when park or neutral are selected.

This will cause premature wear of the clutch plates if the car is idled for long periods after engaging a gear, and can actually burn the clutch plates out if the engine is revved for a period of time. This high rev condition is particularly scary when you consider the process many states require in the process of emissions testing, and also might cause much concern when having the Air Conditioning recharged.

Makes sense to me - but most likely only that specific transmission.

Given how the transmission in the Omega behaves when selecting D after P or N, it almost certainly doesn't keep any of the brake bands (clutch packs, however you want to refer to them) pressurised and engaged.

[Debs.]

Yes, the Discovery ZF gearbox also suffers excessive line pressures in the 'A' clutch-pack if revved in neutral/park; but ONLY when line pressure remains from a recent gear selection (e.g: not likely to do much harm if revved first thing in the morning; before selecting a gear).
Smoke testing a diesel for an MOT test could potentially destroy a ZF transmission....the simple fix is to drill a small bleed-off hole in the piston casing; but why didn`t the manufacturer do it? :-?

[aaronjb]

Yes, the Discovery ZF gearbox also suffers excessive line pressures in the 'A' clutch-pack if revved in neutral/park; but ONLY when line pressure remains from a recent gear selection (e.g: not likely to do much harm if revved first thing in the morning; before selecting a gear).
Smoke testing a diesel for an MOT test could potentially destroy a ZF transmission....the simple fix is to drill a small bleed-off hole in the piston casing; but why didn`t the manufacturer do it? :-?

Because then they wouldn't have a ready supply of orders for replacement transmissions?

[Ian_D]

Yes, the Discovery ZF gearbox also suffers excessive line pressures in the 'A' clutch-pack if revved in neutral/park; but ONLY when line pressure remains from a recent gear selection (e.g: not likely to do much harm if revved first thing in the morning; before selecting a gear).
Smoke testing a diesel for an MOT test could potentially destroy a ZF transmission....the simple fix is to drill a small bleed-off hole in the piston casing; but why didn`t the manufacturer do it? :-?

Interesting, I wonder how many boxes have been damage by MOT testing etc. What age discovery's had the above autoboxes in? I'm thinking about buying an old Range Rover, I assume these will have the same boxes in as a Discovery?

Personally, I rarely rev the car in P/N unless there's a valid reason to, such as checking the operation of the dual ram intake valves and when I had a misfire a while back. Well, besides once when I had the exhausts removed from the cats back... you just have to wake the street up! 

Yes putting the car into a gear when revving is going to cause problems and is a big no-no.

[Marks DTM Calib]

I still struggle to see it given that the toprque convertor will be transmitting bugger all power through to the clutch pack anyway.