dboise

The problem you describe is a very common one with these cars. Mine had the same "rumble strip" vibration when coming out of Overdrive lockup when I first got it. It indicates that the ATF has broken down and is not lubricating correctly. A simple drain and replacement of the transmission fluid in the pan with Toyota T4 ATF did the trick. That's supposed to be done very 25K miles on my car and only gets 2 or 3 of the total of 14 quarts. If your tranny is fairly old, it might not hurt to get a complete flush/refill. That costs around $200.00 around here, but almost half of that is the Toyota T4 fluid itself and its nice knowing the fluid is fresh. Try just the drain/replace of the fluid in the pan first if you like. It worked fine for me and my understanding is that this symptom does not indicate that any permanent damage has been done to the tranny...thank heavens!

My 92 LS400 occasionally surges slightly at neutral throttle, or when decelerating or accelerating to/from neutral throttle. It is most noticable when the cruise control is adjusting to slight uphill/downhill grades and feels like the engine momentarily stumbles. Other than that, the engine runs perfectly. I am about to remove the throttle body and give it a good cleaning, since the car has 200K miles and I know it is dirty. Hoping that helps. I suspect it is also possible that the trottle position sensor might cause this, but not sure. Anyone had this problem and if so, what was the solution? ... Thanks!

For what it's worth, my '92 LS400 (200K miles) developed a vibration which was evident at 1000 revs and more pronounced at 2000 revs. Much worse when driving in gear, but still there in neutral. I changed plugs, wires, rotor/caps, but no help - no error codes from any of the engine/tranny diags. I eventually decided it must be tranny related and went to AAMCO of all places. They correctly diagnosed a cracked rear tranny mount and did a filter change flush/refill, replacing the fluid with Toyota T4 as required. Cost was $257.00, which is most reasonable. Smooth as silk now.