Converter lock up mod

[Toad_555]

Hi all

I'm a new member from the UK and I'm driving my 6th Toyota 4x4, with a past of 4x Hiluxes and I'm now on my second surf.

My question to all you guys is, my current surf is a 3.0 diesel one imported from Japan, its a 4sp auto with converter lockup at 50mph - 80kmh, the 2.4 surf I had before this one locked up at a much lower speed so can I change it without major mechanical mods.

Surely there must me some sort of electronic means to alter it.
I'd like it to lock at about 35mph - 55kmh this would make better use of the engine and reduce my fuel consumption considerably. I think it would also make the truck much more drivable.

Hope someone can offer a bit of info on this one.

Jue. 8)