Torque Convertor Lockup for GU4 3.0l

Hi Les,
The answer to all of your questions is yes. The transmission will change gears normally, even with the converter locked, but because locking it will eliminate all the slippage, you’ll need to rev the engine higher through the gears because there is a much greater drop in revs when you go into the next gear. I find it’s not normally necessary to lock it in lower gears unless you need the engine braking or acceleration, but it is very useful when towing and if you need to lock it earlier or to keep it locked when it continually wants to unlock.

Around the city, I drive normally until I get into 3rd, get up to my cruising speed (usually 60) and then lock the converter. As soon as you touch the brakes, it unlocks and will need to be manually locked again.
If I’m pulling hard or towing up a long hill, I sometimes lock it in 2nd, then take it to about 3000rpm and slip it into 3rd. You can’t imagine how much better it pulls with the converter locked and it feels like another gear change, so I back off the throttle slightly as you would with a manual so the change isn’t as harsh.
On the freeway, I normally do much the same and let the car go through the gears as it normally would to 3rd, lock the converter at 60, then go into overdrive at around 80 to 90.
With the converter unlocked, your car will do what it normally does. All this does is to apply the converter clutch so to eliminate all the slip, but doing this will give you much wider gear ratios and the car will behave more like a manual transmission, so you could stall it if you lock it too soon.
It will work well as long as you don’t lock the converter too early or say, under 1800rpm. If you need to lock it earlier, I would strongly advise that you fit a shift kit to the transmission to increase its pump pressure and the clamping forces on the clutch. This all goes towards a stronger transmission that will live longer.
Chaz

Hi Les

I think Chaz has answered your question Les - best to remember that the system when locked up i much more like a manual but with a very flimsy clutch plate and it can be damaged easily - hence need to match revs better, particularly as its only a 4 speed.

Robin Miller