Hi,

I've recently purchased a 98 4th gen automatic.
I've noticed when driving between 50-60kmph, the engine sounds like its struggling/bogged down and has a drone like noise with some vibration through the gas pedal.
When I turn off overdrive the car runs smooth, could this be a transmission issue or something else?

Thanks.

 

kmph ?

are you talking
60 kilometers per hour
or 60 miles per hour.

is this condition more obvious when going uphill?

how many rpm is the engine turning while this happens.

 

60 kilometers per hour is about equal to somewhere between 35-40 miles per hour and the rpm should be somewhere between 1250-1400 rpm with overdrive on and is in the overdrive gear.

60 miles per hour the rpm should be somewhere around 2000-2200 rpm with overdrive on.

I would say that they are most likely talking about when overdrive is engaged at 35-40 miles per hour and the engine rpm drops to the range of 1250-1400 rpm. This is normal behavior unless you get ses lights which may indicate a different problem.

 

Maybe low octane gas and it’s detonating under the overdrive load!

 

The owners manual states that 5th gear can be used after 45 mph. That's 72 km per hour.
I think that overdrive on the automatic transmission should not be used below those speeds.

I'm guessing that the original poster is using the overdrive when the car is travelling slower than that.