Floods

[Doofus]

I have recently had to drive through deep floods on two occasions in my 2008 LC 5 Invincible and both times the truck slowed down while the engine revs increased. We were on tarmac roads and the water about 500mm deep, enough to set off the parking sensors. It's fine going through shallower water, the speed and revs remain constant and proportionate to the throttle position. But in deeper water, she slows down and the engine revs increase regardless of my foot on the throttle. It is almost as if she changes into low ratio or (if it wasn't an automatic), the clutch is slipping. Is this normal and if so, what is causing it?

 

[clivehorridge]

Were you floating?

Not such a silly question...

 

[Chas]

Sounds like the auto gearbox is just changing down on meeting a resistance like going uphill would be, I'm sure somebody will be along soon to prove me wrong.

 

[fridayman]

How fast did you enter the water?

I agree with what Chas says about kicking down.

 

[Crispin]

I would say the TC unlocked and/or the gearbox kicked down. My 150 does exactly the same.

500mm is not floating territory, IIRC, the wading depth was 720 or 750 for the 120.

When I had the manual 120 I was amazed at how much effort is needed to go through bumper-deep water. Caught in the wrong gear and the engine just dies.

 

[Graham]

Really not floating.

One needs some thing like the water level with the bottom of the door windows, then the rear wheels lift off, engine weight keeping the fronts in contact.

Probably the auto-box just doing it's job.

Gra.

 

[Doofus]

Cheers guys. I think the changing down sounds right, I certainly wasn't floating - I just didn't expect the pressure of the water to be so great as I entered it pretty slowly anyway.