Transmission Shifting Help Please - '98 Gs300

Humphreys · January 22, 2007

I recently (2 months ago) bought a one owner '98 GS300 with 150k miles, all scheduled maintenance, all service records. Car has been running super but about three days ago I noticed a new issue with the transmission at highway speeds.

Basically at 65+ mph the transmission will downshift at the merest hint of pressing the accelerator. It will also downshift on slight freeway inclines. Downhill, or when I let up off the accelerator, it will return to overdrive. At 70 mph we are talking about 200-300 RPM difference and a noticeable shift - so I am assuming it is shifting, not slipping. It also feels like a normal smooth shift, not jerky, but I just don't think it should be downshifting, and it wasn't a week ago.

This is the first automatic I have owned so I am a bit of a newbie in that respect. I have read on here that the transmission is electronic and can "learn" different habits. I had driven it in Power mode until a week or so ago when we had major snow here and have now used that "Snow" setting quite a bit this week. Didn't know if that might confuse things, or perhaps the mode switching is contributing to confusing the computer.

Any ideas / suggestions would be appreciated.

One thread I read noted disconnecting the battery to wipe the transmission "memory"? Good idea?

I appreciate any help. Thanks.

Mark

dcfish · January 22, 2007

I recently (2 months ago) bought a one owner '98 GS300 with 150k miles, all scheduled maintenance, all service records. Car has been running super but about three days ago I noticed a new issue with the transmission at highway speeds.

Basically at 65+ mph the transmission will downshift at the merest hint of pressing the accelerator. It will also downshift on slight freeway inclines. Downhill, or when I let up off the accelerator, it will return to overdrive. At 70 mph we are talking about 200-300 RPM difference and a noticeable shift - so I am assuming it is shifting, not slipping. It also feels like a normal smooth shift, not jerky, but I just don't think it should be downshifting, and it wasn't a week ago.

This is the first automatic I have owned so I am a bit of a newbie in that respect. I have read on here that the transmission is electronic and can "learn" different habits. I had driven it in Power mode until a week or so ago when we had major snow here and have now used that "Snow" setting quite a bit this week. Didn't know if that might confuse things, or perhaps the mode switching is contributing to confusing the computer.

Any ideas / suggestions would be appreciated.

One thread I read noted disconnecting the battery to wipe the transmission "memory"? Good idea?

I appreciate any help. Thanks.

Mark

Mark

Yeah, Disconnect the neg. terminal for a few minutes and that will reset the ecu. ;)

Welcome to the club :cheers: