Transmission problems. What should I do?

Hi all. I drive a 98 Lexus gs 300 w 160 k miles. Recently while driving down a very steep mountain the car slows from 75 to 60 mph and the tach is at 2000 rpms. When I go to give it a little gas the transmission doesn't respond it can't find the gear it's lookng for. Eventually the tranny kicks back in and 5 minutes later everything is back to normal.

How concerned should I be? I've made this 5 hr trip before many times and this is a first.

I appreciate any input

Reply to
H Z
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Not to discourage usenet use or anything, and this is not meant to supplant any useful info you might receive from folks in this thread, but my recommendation is to go to these forums, create an account in the GS section and describe your symptoms (after searching for existing threads on the topic of course). You will find a wealth of info there.

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Reply to
Mark

When is the last time the transmission was serviced, and what is the condition of the ATF? What position was the gear selector in at the time?

Reply to
Ray O

I also thought I'd mention this happened only 1 time on each trip only while going Down a very steep mountain. The first time I didn't think anything of it... the second time on the return trip was cause for concern. I don't think it's a normal condition as it never happened before during this same route (San Diego to Las Vegas).

Ray has been here for me for many years now. It's an answer I know I can trust as opposed to club lexus.

Reply to
H Z

Your car slows from 75 to 60 down a very steep mountain? I suggest selling your car and getting a bus pass. You're dangerous.

Reply to
Virgil Skankman

Is this your first time visiting alt.autos.lexus?

Reply to
DaveW

So you slow the car going down a very steep mountain by letting off the gas, doing 75. You certainly should not be driving. Take the bus.

Reply to
Dweezel AnalRetentive

I spoke w/ a Lexus Master Technician today who said that my problem is that the sharp decline of the mountain rushed all of the trans fluid to one side of the car and that's why I was having problems only in that situation. An answer like that actually makes sense to me and that's the best he can do w/o looking at the car.

His diagnosis was that I didn't have enough fluid. However, according to the dipstick I am at full. So for now I may just keep the car locally and avoid long mountainous road trips for awhile.

Does the master technician's answer sound possible?

Reply to
H Z

The answer is possible if the ATF level was low, however, it is easy to confirm whether or not the answer is correct. Under the same exact conditions, the vehicle will exhibit the same behavior.

To answer your earlier question, it doesn't sound like the incorrect ATF was used because the vehicle would exhibit problems under a wider variety or driving conditions. I asked the question to see whether the ATF had deteriorated, which it doesn't sound like. ATF is much thinner than motor oil, especially when hot.

In your original post, you said that the transmission didn't respond when you gave it gas, but did the engine respond?

Your transmission will downshift under certain conditions, and 2,000 RPM while going down a fairly steep road doesn't sound excessive. If the transmission upshifted when the grade leveled off and the ATF is translucent and pink (and the correct ATF is used), I wouldn't worry.

Reply to
Ray O

Well when I checked the condition of the fluid via dipstick it seemed ok but on a closer inspection I may have solved my own question. Please visit the following page.

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The first glass is fresh ATF fluid w/ a cranberry juice type color. The second is ATF as it came out of the car. It had more of a grape juice color. At the same time fresh motor oil looks much different than motor oil that's been used even just a couple of times. From what I remember fresh motor oil is a honey color but after just a little bit of use it turns black right away.

Ray, can you confirm that the condition of the ATF is so bad that it is likely causing the problem or could it be something else? I feel like I should be worrying because this is a new situation that has never happened before.

Thanks much..

******** In your previous post, you mentioned that when you hit the gas, the tachometer would indicate an increase in engine RPM but that the car would "stall" a bit.

The computer that controls the transmission looks at inputs from several sensors to determine which gear the transmission should be in, and whether or not the torque converter should be locked or unlocked. Among the inputs are vehicle speed, throttle position and whether or not the brakes are applied, and from the various inputs, the computer infers whether the driver is trying to accelerate, cruise, coast, or whether the vehicle is going down a long incline.

Unfortunately, I cannot conform that the condition of the ATF in the photo is so bad that it is likely causing the problem, but if there is enough contaminants that the fluid is opaque, it is a good idea to change it. Does the used ATF have a burnt toast smell or smell significantly different from the fresh ATF? If so, the ATF needs replacement.

Automatic transmissions have numerous internal clutch packs, and the friction surfaces wear just like the friction surface on brakes or on a manual transmission clutch. ATF becomes dark because it becomes contaminated with the worn friction material, kind of like how a car's wheels become dirty from brake dust material. Eventually, the contaminants in the ATF will affect the movement of spool valves, solenoids, and how the friction materials act enough so that the transmission doesn't shift or hold gears properly.

Judging from the color of the used ATF, I would change it but do not have the transmission flushed because flushing a high mileage transmission tends to cause problems.

Reply to
Ray O

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