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'96 LS400 transmission behavior?

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Old 11-19-11, 12:20 PM
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Rdrcr
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Default '96 LS400 transmission behavior?

My LS400 runs and drives great but, I do have a question regarding the transmission behavior that I do not know if it is normal or not.

Please forgive me, I'm not familiar and have no experience with the specifications regarding this transmission. So if my description of the problem is not accurate to the actual specifications and functionality of this transmission, I apologize.

While driving at moderate speeds on the highway or streets, say 45-55mph with a very light throttle application, the transmission seems switch between a lockup and non-lockup position. Basically, it feels like the transmission is hunting between gears at those speeds even though I know it is not actually shifting. Further evidence can be seen by watching the tachometer rise and fall by a couple hundred rpm without the accelerator pedal being pressed.
The transmission behavior is similar ( but, not to the same degree) to my old Camaro Z28 with a 3,800 stall torque converter. The rpms climb while you are accelerating but, once you finish acclerating and are cruising, the rpms fall to a near idle rpm if you are not on the gas pedal.

Is this normal?

I have read that some folks have had issues AFTER they have had their transmissions serviced so I wanted to see if I could get an explanation of this issue before I have anything done.

Thanks,

Mike

Last edited by Rdrcr; 11-19-11 at 12:32 PM.
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Old 11-19-11, 12:41 PM
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billydpowe
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I dont know, but I hope it is, my 96 seems to "float" at that speed also, with out really changing gears, very little rpm change, 1 to 2 hundred.... it performs all the power shifts properly.... I figured it was the "lockup" converter not knowing what to do..
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Old 11-19-11, 01:40 PM
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Originally Posted by billydpowe View Post
I dont know, but I hope it is, my 96 seems to "float" at that speed also, with out really changing gears, very little rpm change, 1 to 2 hundred.... it performs all the power shifts properly.... I figured it was the "lockup" converter not knowing what to do..
smiles....
Good to know. Thank you.

If the transmission behavior is normal, I can't understand how Lexus allowed it to be so noticable while driving. Perhaps, it has something to due with the age of the transmission fluid or the age of the car. I don't know?

I'm sure my transmission has not been serviced in some time, so I will have it serviced along with a few other things that need to be done when I bring it to the dealer sometime next month.

Mike
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Old 11-19-11, 01:40 PM
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Damn Billy, you just like posting pics of your new LS anywhere, even in a tranny thread, Just kidding, you must really love it. My 93 has had that same sort of skip at 40-45 for about a year now, same way you're describing it. I think mine is caused by the TPS though, at least that's what some people have said it could be. I don't get a code for it but it's not in spec when I tested it. Funny thing is I have a used TPS sitting right in front of me on my desk, just don't have the enthusiasm to change it, I keep putting it off.
Check your TPS to see if it's in spec.
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Old 11-19-11, 02:45 PM
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You are in that dead spot of having it in final gear so it hunts. Changing throttle pressure doesn't help it in make a decision because that between shift.
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Old 11-19-11, 06:10 PM
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Originally Posted by deanshark View Post
Damn Billy, you just like posting pics of your new LS anywhere, even in a tranny thread, Just kidding, you must really love it. My 93 has had that same sort of skip at 40-45 for about a year now, same way you're describing it. I think mine is caused by the TPS though, at least that's what some people have said it could be. I don't get a code for it but it's not in spec when I tested it. Funny thing is I have a used TPS sitting right in front of me on my desk, just don't have the enthusiasm to change it, I keep putting it off.
Check your TPS to see if it's in spec.
I do Dean, I feel blessed to have run across it, even with my blinking t/off.
it turned over 183k today, runs and looks so good, I am satisfied .
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Old 11-19-11, 06:18 PM
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My car has a violent lurch as it engages into OD. I chalk it up to having an awful transmission. It really holds our cars back... along with the engine management. With a 6-speed these cars would be faster than the LS430s.
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Old 11-19-11, 06:39 PM
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the trans in the LS is the same as those in the GS/SC/Supra of the same period. If there's something wrong with anything it's probably YOUR transmision, not all of them.

and no, adding a 6th gear (which was added to the '05+ just for fuel economy) still leaves you down ~60-80hp and 50lb*ft of torque.
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Old 11-19-11, 06:54 PM
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Yeah thats not normal for a A340.
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Old 11-19-11, 07:07 PM
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Originally Posted by PureDrifter View Post
the trans in the LS is the same as those in the GS/SC/Supra of the same period. If there's something wrong with anything it's probably YOUR transmision, not all of them.

and no, adding a 6th gear (which was added to the '05+ just for fuel economy) still leaves you down ~60-80hp and 50lb*ft of torque.
But - also down 200-400lbs, and a 6-speed with more performance oriented gearing and less internal drag (i.e. a modern trans) to keep the motor in its sweet spot longer would definitely give that LS da eddddge
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Old 01-16-12, 09:42 AM
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UPDATE:

I finally got my LS into the local Lexus dealer for an oil change, fuel filter replacement, and to service the transmission (transmission flush). Surprisingly, the transmission operation has been drastically improved. The transmission no longer hunts or fluctuates between gears and RPM's like it used to while driving on the highway in light throttle applications. It will still drop RPM's when you foot is removed from the accelerator or when you come to a stop but, that's the way it should operate.

Anyway, big improvement. Makes me wonder if the transmission was EVER serviced during its previous ownership.

Mike
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Old 01-16-12, 10:51 AM
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Glad you had it serviced...now the car and you will be
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Old 01-18-12, 04:23 PM
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Just out of curiosity, about what did the dealership charge you to service your transmission? I want to have mine serviced soon and I just don't have the time to do it, so I was going to take it somewhere. lol
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Old 01-19-12, 09:52 AM
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^^^^
I don't know if I can give you an accurate estimate. The company I work for owns our local Lexus dealer and we get a pretty significant discount on parts and labor. That said, I believe it was around $109.00 for the service which included 12 quarts of ATF fluid, an additive, and the labor to perform the flush.

Hope this helps.

Mike
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