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birdman

1990 Ls400

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I just recently bought a 1990 lexus ls400 and I was wandering what the purpose of the trans lock button was?I also noticed that when I'am driving at highway speeds and I let off the gas It's like a brake is being aplied, can anyone tell me what this is.Do not have a owners manual.Thanks.

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When driving on the freeway- are you sure that it is in "overdrive"? Make sure that the "O/D OFF" light is not illuminated on the dash. You can also tell by looking at the switch on the gear selector.

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the lock button is to overide so you can change gear with out the key in the ignition or the brake depressed. its convinient when you need to move your car quickly when the battery is unplugged or something.

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Thanks for the info.But the transmission overdrive is switched on.So I still don't understand why when a high speeds that it feels like a brake is being applied when I let off the gas.

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Parking brake is off everything is normal.When you let off the gas and it feels like a brake is applied if you press the gas again it's like the car jerks.

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You may be feeling the 4spauto trans. When you have time, I would suggest you throughly warm-up the block, and from 0mph, watch your RPMs as the gear shifts. Do this slowly so that you can watch each gear shift. On my car, I make my gears shift at 2000RPMs, and time it. It's possible one of your gears will shift late, but the status quo for all LS cars is to shift equally(time).

Check out your gears first, and do you have any error lights ON?

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Gas pedal lift / engine braking...

My guess is that you are in the process of transitioning from a FWD vehicle to a RWD LS. Most modern FWD automatic transmissions are designed to virtually eliminate engine braking due to the hazardous of loss of control of the vehicle that will often result from engine braking at the front wheels on a slippery surface.

The transmission designers for FWD have no way of knowing if the surface is slippery or not so they tend to err on the side of safety.

I had virtually the same experience recently while test driving a new BMW X3. The X3 is AWD with predominant engine torque normally to the rear so it exhibited, to me, rather extraordinary engine braking when I got off the gas fully. My normal wheels are an 01 AWD RX300 which is definitely FWD torque biased, 95/5, and Lexus has gone to extraordinary measures to assure that the engine lagging toque on throttle lift has little or no effect on the front "drive" wheels. The Lexus seemingly upshifts, or maybe even shift into neutral, when coasting with throttle lifted.

Quite some years ago now Cadillac started using an over-running clutch within the transmissions of FWD caddy that used the high torque Northstar engine because too many old codgers were dying due to loss of control from the severe front wheel braking effects. Since those folks are/were the primary market for caddies GM had to pay attention before the marque lost too many buyers.

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