Shaffer

The problem I am about to describe about my Lexus has happened three times- once last week and twice a few days ago and twice 2 days ago.

The other day I was driving on the parkway at a steady speed of about 45-50 mph- the car was in 4th gear and the lock-up was activated. I pressed the accelerator to gain speed to go around a slow car and while it was upshifting- there was a very quick vibration sound immedietly after it kicked in out of the lock-up mode. The sound lasted for only a second. The sound was virtually identical to running over one of those white "wake up" strips on the road at intersections, but there was none there where this happened. I tried to duplicate the problem and it did it again. I tried it a few more times and it did not do it. Last week- it only happened once- again, while accelerating and the car upshifting- as if I had hit a wake-up strip, or a imperfection in the road like the trackloaders cause. Does anyone have any clue as to what this could be? My transmission? Differential? Other than this- my transmission operates fine. The shifts are very smooth and no slippage. When I gradually accelerate to make it shift out of overdrive- it does not do it. Any information appreciated.

Someone else on "Lexus owners club" has the same problem, but only worse. I plan on taking the car to a transmission shop tomorrow, but wanted to get some info here.

SharpLS-96

Sounds to me like it might be a problem with your "Rear End Differential" rather then your tranny.
BTW, when was the last time you changed your rear end fluid?

Read the 2nd paragraph on here, is this what your experiencing?
http://www.usedcarbuyingtips.com/use.../rear-end.html
"Bad universal joints, sometimes give you a vibration at high speeds in either the floor or body of the car."

Shaffer

Thanks for the reply and that link. It does have a faint, steady, & quick vibration at times, at speeds between 45-60. I do not think it is the tires causing this. I drove the car again today on the highway and tried to get it to do it (the sound upon kicking out of overdrive) again at 60 mph. It does not do it at that speed. It seems like it has that sound (like hitting wake up strips) only when I rapidly kick it out of overdrive at about 40-50 mph. I have only had the car for about 3 months, and never have checked / changed the differential fluid. Other than that- the differential sounds quiet- I do not hear any "whines" from it or anything. What in the differential could possibly make this "wake-up strip" sound, or "slipping cogs" sound while this car is coming out of the lock-up torque converter mode, upon heavy acceleration? Thanks again.

SharpLS-96

Well, two possible causes that come to my mind are:
1- A bad/worn "drive shaft centre bearing". If the bearing is very badly worn and moves from side to side several mm it causes the drive shaft to vibrate at resonance speeds which is what you might be feeling.
or
2- Bad "Universal Joint"

Try to take the car to someone who specializes in drive shafts and rear ends in your area.

On a side note, I would have the rear end fluid changed since you don't have any service history for it and decide not to investigate the problem any further.