Hello,

Long time reader, first time poster here. I've been eyeing 4th gen GS350 for awhile. I test drove a couple, a 2014 and a 2015, both non luxury/non F-sport. I was surprised at how differently they drove. The 2014 had some vibration, it felt like a 15 year old car that's never had its spark plugs replaced. In sport mode, it held its gears and the rpm dropped slowly when I came off the throttle. There was significant engine note difference once the car hit 3k RPM.

The 2015 was super smooth, however in sport mode it did not hold gears and RPM dropped immediately when I came off the throttle. I did not notice significant engine note difference when the car went over 3k RPM in this car.

Vibrations between the two cars can be written off as sample variance in used cars, but I'm surprised at the way the engine sounded and transmission behaved between these two cars. Has there been programming changes between 2014 and 2015 that can explain such difference?

 

I do not have an answer to your question but did you just do one pull for a test?

was this the same road and tires? Hard to say vibrations were so different if you are running different tires on a different road

 

I do recall there being some adjustments made in 2015...

 

This is correct. Structural elements were changed to increase overall stiffness but I believe they were fairly minor upgrades along the lines of using stronger windshield adhesives and what not but this would likely explain the higher levels of vibration and older feel of the '14. IIRC, different suspension parts were used to give the GS a sportier character and less luxurious/floaty ride as well for the '15 year forward.

 

I have the 2014 non lux, non F sport and i haven't noticed any vibration. it just its and gets.

 

The vibration the OP noticed may have been caused by the car sitting for an extended period, which will flat spot the tires until it has been driven for awhile.

 

Exactly! I have had this experience before with two brand new cars from the same model year, one with vibration and the other without. The other possibility could be that the tire pressure/balancing/alignment are out of specs.

 

Or you could have a bad front end part loose or worn ball joints or tie rod ends.

 

 

Owners with '14 should not feel any need to defend their purchase or have buyer's remorse regarding vibration. That '14 car for all I know could have been in a serious accident that was just not showing up in CarFax. And I don't feel that vibration is an important difference in this '14 vs '15 comparison.

I am more surprised at the way the transmission behaved between those two cars. I may need to test drive more samples of '14 and '15s to determine if sport mode behaves this way across all 14s and 15s.

 

The 8-speed transmission in both the '14 and '15 non-AWD is the same. The difference you detected (or felt) in the transmission may have been caused by the car's engine/transmission not having been close to normal operating temperature, where the signal inputs to the ECU alters the operation of both the engine and transmission.

 

There are so many potential culprits of vibrations (including the road); literally could have identical cars that behave with different road manners.

There should be a Lexus (or sales rep) with every test you do so you can have them be accountable for admitting there is an issue to be addressed. Dealing with used cars - you have no idea what really happened with it and can't make a blanket assumption about an entire model year. That's just unjust.

 

See below, quoted from my OP. No one has made any blanket assumption in this thread about vibrations for a specific model year.

 

Operating temperature difference is something that I did not think of. I think this is the best theory thus far. '15 was driven in colder weather, it makes sense that ECU would not hold lower gear when it hasn't come up to temperature yet.

 

Well good luck...