getzac

Hi guys,

My lexus ls400 has 180k miles and recently developed a strange problem. It does not shift how it used to. 1st gear shifts pretty much immmediatly at around 4000 -5000 rpms even if you were to floor the pedal down. 2nd gear is fine and then it jumps into 4th gear.

i took the car today and tried selecting the gear manually like 4th 3rd 2nd and it seems to me it downshifts into second only and if the shifter is on any of the three geard upon releasing the accelerator the rpm falls down to 500. But if i press down it kinda goes up to like 2-3000 rpms and then selects the gear again.

Also the PWR and ECT fucntions dont seem to exist anymore and upon selection they dont illuminate on the dash either. Snow function does illuminate upon selection but the gear chnage is the same.

So xan anyone help me in the right direction. I tried couple of OBD scanners and they dont even communicate with the ECU. So im more of a blind bat. Could it be gear solenoids?

I have checked the ECU and all the capacitors seem fine.

JetCat

Hey Getzac ... sorry to hear of your transmission problem. I had kind of the same thing going on with my 95 LS400 at one time .... in my case, the shifting was kind of hard through each gear .... it just did not seem right. We ended up doing a total flush of the entire transmission and then changing the transmission filter. That fixed my problem. Just for fun I have added some Prolong Transmission Treatment and it seems to have smoothed things out even more. By the way, when I say " flushed the whole system" what I mean is, we ran about 19 quarts through it with a flush machine ... and then refilling it with the correct spec Toyota fluid ( thus we used a lot of fluid for this job ) My old fluid was very, very dark. Now my fluid is bright pink and does not stink ... and ... my shifting is smooth again just like it is supposed to be.

This is how it went for me ..... no problems ... kinda expensive ... but no problems. I did this about 35,000 miles ago .....
I hope this may help .. .. .. ..

Yamae

The answer seems to be in your statement above. I'd simply check the ripple level explained in the FAQ first since 2 scanners don't communicate with the ECU.

JetCat

GETZAC ... somethingcame to my mind today about your situation here . . just food for thought : in some transmissions there are solenoids that depend on non-restricted fluid flow. Problem is, sometimes these little solenoids have a stainless steel fine mesh filter screen on them that becomes clogged-up over time ... usually associated with transmission fluid that simply is not changed enough over the years .... no offense or anything ... but lets face it, most people just do not flush their transmission fluid ... sometimes never, ever is it done ... so what can be expected eventually, are that these little solenoid filter screens to become clogged .... thus causing highly restricted fluid flow ... thus causing shifting failure.

Do our Lexus transmissions have these little filters in them? Honestly I do not know. I do know many of the Honda Transmissions do ... and I think there are indeed some Toyota transmissions that do ..... but on a Lexus ... I have not seen one taken apart yet, so I do not know . It is certainly a possibility .. .. ..

OK ... so what to do about this on the cheap? I have an idea. Run some Auto-RX through your transmission for about 1,500 miles and see what happens. Why Auto-RX? Because Auto-RX is said to liquify the grime and tarnish away which is how it cleans engines / transmissions. https://www.auto-rx.com

I have used this product many times with great success .... yes ... even in a transmission. Because of the cost I do tend to leave the product in a little longer than they suggest.

So let's say this was my transmission on my car ... frankly I would probably run the Auto-RX for as much as 2,000 miles, unless along the way the shifting started to work normally again sooner ... then I would finish by doing a total maxed-out system flush ... then ... I would change the filter as a last step. I would also use the correct Toyota fluid as a refill.

I will say I run several ounces of Prolong Transmission Treatment in all my transmissions ( I have 6 cars ) ... they all are working perfectly providing perfect shifting ... and as you might guess .... all my transmissions have bright pink fluid that does not ever smell burnt .... : )

Sooooooo ... just thinking out-loud here ...... perhaps this might help? I hope things work out for you .....

RA40

iTrader: (6)

+1 to check the ripple of the ECU.