My '98 GS400 with 115,000 miles just started an odd slipping/reving under mild acceleration. It is almost as though it is slipping into neutral or that it is dropping a gear unexpectedly. I obviously lift off the accel and it goes into proper gear and works fine.

It has gotten regular fluid changes and I am the original owner. I have not noticed it if I put the transmission into sport mode. Should I try swapping the fluid (changed it probably 6 months ago) or do you think I may need to flush the valve body?

I didn't see anything with a quick search to reflect any known issues.

Thanks

 

One quick question. Does the check engine light come on when this happens?
If it does there is a possibility it's just a frayed wire going into your trans. and your lexus dealer can check it out. Happened to me last fall and I almost had a heart attack. Lexus dealer fixed it for one hour of flat rate.

 

Do you mean the engine winds up and then all of the sudden it catches gear?

 

I have the same problem, did you ever get this fixed??

 

dude idk but the gs4 tranny is weird....it revs so high going downhill that i have to put it in neutral to keep moving or it will slow me down considerably on the highway. im talking revvin a grand over what i know it should be. nothing ridiculous. i think it gets tripped up, and this is very very clear in the city.

 

austin, your transmission is most likely in a lower gear going down hill to save you a bit on braking. Engine braking kicks in if you're going fast enough down hill without giving throttle.

 

im having the same problem in my 300 let me know if you find out what it is

 

Did you guys replace the tranny fluid? you usually change it around 20g's...

 

Have you flush your trainny lately? Mine was acting a little weird last month during stop and goes, and I could hear the gears shifting and it was not smooth at all. Then I flushed out my trainny fluid, and it's now running normal agai. No jerky, any sign of slippage, or revin up. I am not sure this is will apply to your problem, but I just want to share from my point of view. It is so easy to flush out the trainny fluid, but you will need another person to assist you to turn off the key and back on during the process. Let me know if you decide to go this route which is a lot cheaper. I like to start with the cheapest fix first and work my way down the list. Also, there were an article on how to flush the trainny fluid if you seach it, I think. Good luck.

 

I had this same problem in my IS300 from 90,000 miles until I sold it at 150,000 miles. Lexus or any other mechanic could never do anything about it. There was also a high pitched squeak when it shifted gears. You couldn't hear it unless you were listening for it. I had regular fluid changes and it never gave me a problem. The downhill high reving happend in my IS300 and now in my GS430. If you don't hit the brakes it doesn't downshift.

 

Check your battery and flush the fluid (use toyota Type IV)

 

usually getting your atf flushed fixes that problem, OR your guys can possibly be looking at a speed sensor.. thats whats happening to me right now. last week my car stuttered and has that high pitch squeek when it shifts with a "slipping" clutch from time to time. got it flushed and it went away. but check engine light came on and im taking it back to the shop today, soo my mechanic said its probebly the speed sensor. but not for sure yet..