Which T model ride better( t-660-t-680)

Suspensions are pretty much equal, so it should be more the same if you have matching wheelbases. The 680 sleeper is more spacious... it's more like the T2000 or T700 sleeper than the traditional Aerodyne sleeper. Been seeing a lot of blown wheel seals and electrical issues with the 680, though.

 

T680 is way more comfortable, quitter, more room, but not as big as the 700

 

the best part over the 660 is the flat floor so you don't trip into your bunk

 

The 660's sleeper with the optional 86" studio may be bigger inside (in floor area) than the 680's, but not the cab or headroom. I was considering a new 680, but being as they are a new model they have some issues. The 660 has been around for some time now , and that's given KW time to work most of the bugs out of them. And there's some pretty good deals on low mileage, optioned-up 660's out there.

 

After driving both the 660 and the 680, the T680 is way more comfortable and roomy as well as very quiet inside while rolling.. There are two air suspensions available on the 680. The one that has the spring looking attachment that goes over the axle with the shocks mounted inside the frame rides much better. I have owned one of each of the suspension types. I have averaged 7.0 mpg with the Cummins ISX15, 9 speed manual. The fuel mileage alone, with the comfort and quiet made it a hands down decision. I loved the T660 until the T680 came around.