Hey all, I have two very specific transmission-related problems with my 1999 Toyota 4Runner (Limited trim, 4x4 automatic with O/D, 138K miles).
First off, for 99% of the driving I do, the transmission shifts GREAT, both up and down through the gears.
Problem #1: Shifting into reverse is harsh. Especially in the morning after a cold start. It takes about 1 second to engage, and it does so with a jolt. Not a big deal, but it's annoying.
Problem #2 (and this is the big one): After driving with the torque converted in lock-up (above about 40 mph) for an extended period of time (say a typical highway trip of 40 miles), and I come to a stop, the transmission will act as though it's in neutral. Depressing the accelerator just gives me revs. The best way I've learned to get it back into gear is to manually shift down to low (1st gear). This usually works, with about the same amount of "jolt" as shifting into reverse. Then, I just shift up into drive once I'm moving, and all is good again. If I've been on the highway for a LONG time (say, 200 miles without stopping), sometimes this symptom can happen at 2 or 3 stops, not just the first one. In all cases I need to shift down to low to get it to engage in drive again.
Recent service (1,000 miles ago) included a trans fluid drain (about 8 quarts, said the trans tech) and filter replacement. I have noticed no improvement in the problems. The fluid level is correct, having checked it with the engine and transmission warm, idling in park.
Lastly, and perhaps most importantly, I noticed these issues not long after having to replace the ECM in the truck. I went through an automatic car wash and some pressurized water came in under the dash and shorted something in the ECM. After taking that ECM out and inspecting it, it's obvious it's seen plenty of water over the years from this leak. So, I replaced it with an ECM out of the same year vehicle. I had to have my transponder keys programmed into it by a mobile locksmith, but it fired right up and has been running great ever since. The only issue is this wacky shifting thing.
Any ideas? I've narrowed it down to:
- ECM not sending the shift signal
- VSS (vehicle speed sensor) not working 100% of the time
- TPS (throttle position sensor) getting stuck after sitting at one position for a long period (cruising on highway).
However, none of these (with maybe the exception of #3) seem to explain why the truck shifts JUST FINE at all other times.
Thanks for the help!