Quick question for the car folks. I’ve a 2005 Camry (automatic) that has developed a strange vibration when the tranny is in O/D. This coincides with an unexplained drop in mileage (down about 4mpg). The best description I can offer is a sort of low-frequency “thrumming” when the car is fast enough for O/D, and under a load (as in climbing a hill). At first, you would think it was a washboard road surface, but I discovered I could make it happen at will by applying extra power.
What could cause this? Is there some sort of clutch that engages when the transmission reaches its final gear? I’ve always thought there was only a fluid connection between engine and wheels.
It’s almost due for new transmission fluid. Is it possible this service would help? Or does it sound like I need to prepare for a large monetary donation to the Toyota dealer? Or is this indicative of something that can be adjusted?
I know it’s a lot of questions from a description of a noise, but maybe one of the experts has encountered this and can shed some light.
Yes. Modern cars have what is called a “lock up torque converter”. It’s just like a normal torque converter (it’s just fluid between the wheels and the engine) until you get to highway speeds and such. Then the torque converter “locks” and you end up with a solid connection between the wheels and the engine like you have with a clutch.
It’s more efficient than the old fashioned torque converter because you don’t lose energy sloshing all of that fluid around while it’s locked. It’s one of the main reasons that automatics get almost as good of gas mileage as a manual these days.
I don’t think you’ve got a problem with your torque converter. I think you’ve got some sort of problem with your OD gear. But, I’m just a backyard hack mechanic and I don’t have much experience with transmissions, so I’ll let one of our real experts tackle that aspect of your question. I just wanted to let you know that yes, there is something in there that acts kinda like a clutch.
I didn’t know the tranny had a direct hardware connection when we were up to speed (thought it was all software :p). I wonder if that “lock up torque converter” (LUTV) is rapidly slipping and re-engaging. That’s definitely what the car feels like.
A bit more experimentation showed that I could stop the problem by pressing the O/D lockout button on the shift lever. I assume this stops the tranny from trying to shift into its final gear, and maybe prevents that LUTV from trying to engage. I’ve told the missus to drive the car with the O/D lockout engaged until I can get it in the shop. We’ve an appointment with a trusted mechanic (not the Toyota dealer) on Tues. I posted here to try and arm myself with as much info as possible before the mech visit. I’m actually a decent shade-tree mechanic on some of the simple stuff like brakes, bearings, coolant hoses, belts, etc. But transmissions are a mysterious black art, and I’m about to face the wizards.
2003 Camry owner here, but I’m no expert in auto stuff.
I’m fairly sure that the “lock-up converter” in the Camry only engages once you are in O-D, that will explain why you do not experience the problem when you switch it off.
However, that does not give any indication if the problem is with the O-D gear as mentioned above or with the lock-up slipping.
Myself, I would guess it is slipping.
With my previous Camry, a 1991 4-cylinders, I could tell when the lock-up engaged with a little drop in RPM, with my current one, a V6, I usually do not notice the difference.
Pay attention when you accelerate, if you can notice the O-D engaging and then the lock-up, you might be able to tell when exactly the vibration starts, this might be difficult to tell because of the number of gears today, 5 (6?) with the O-D compared to 4 in my old 1991 Camry.