When I get on the freeway, and hit about 80-85 the car starts to make a whirring noise, that is very annoying. Now a mechanic told me that you shoulf leave the overdrive on, is this normal, or is there something wrong?

I have a '90 LS400.

 

I'm really not sure what the whirring noise is...any chance it's air leaking into the cabin or just some type of turbulence caused noise? Does it come from inside or outside? Then again, you mentioned that it seems to be specific to a certain speed. Usually, when it only occurs at a certain speed, there's a good chance it has to do with the wheels needing to be balanced or maybe the tires being out of round, but it's not usually described as a "whir" type noise. Does it go away if you speed up or slow down?

As far the overdrive goes, the mechanic is right--you should leave the O/D ON unless you are towing or driving for long periods though mountains where there are lots of inclines and declines. Generally when overdrive is off the automatic transmission does not go into its top gear, hence you have more power, and for decents, engine braking is used instead of constant braking (personally though, I'd prefer to use my brakes, but I can see where brake fade and over-heating could become an issue). For everyday driving, you definitely want to have overdrive on. If you've been driving with it off, you've been working the engine a lot harder and you've also been getting fewer miles to the gallon. Turn it on and I guarantee you would see a difference in your mpg.

Depending on what you're driving and its condition, it's possible the whirring you describe is the engine screaming for mercy--if your overdrive is off, then the engine is at a significantly higher rpm and if you're in say, an old domestic truck where the speedo only goes to 85...you see where I'm going with this? No offense, just trying to illustrate the problem leaving the O/D off.

Turn the overdrive back on and if the noise goes away, then you're set. If not, then refer to the first paragraph and tell us what you find.

Mike

 

Thanks man!


To be honest, I have had the O/D on always and the noise has went away. I am very happy, and right now my baby is in my uncle's garage getting EVERY single mechanical system flushed out.