05' vnl64t670

company driver ?
ISX+13speed trans/10speed its fine over 500HP
Best on market pulling and Jake brake
engine eat fuel like hell 4.5-5.5 mpg
Egr problem,head gasket,head,injectors,turbo 3500$
some Isx quiet some noise i have no idea why
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I own 2006 volvo 670/D12D/465hp /12 speed FreedomLine trans.
856561 actual miles 6.3 MPG for All miles

 

so we have one luckiest guy with d12 never heard about head and head gasket in ISX and injectors too... noise, yes i agree and that's a problem with a exhaust manifold gasket or turbo - exhaust gasket which i already fixed in my ISX ,egr ,hmmmm but owners who cares simply disconnect egr plug and you will be happiest dude on the highway
good luck
p.s. d12 think about your egr cooler ,egr ,crankcase preassure and you can't do anything in the computer without dealerships and spending tons of money there like other engines can be threaten...

 

05 or 06 try to find a spring ride font axle.

d12d is a solid engine, fuel mileage and power leave a little to be desired but if you block the egr system the mileage and power come up. it is super quiet too

as far as parts go they are no more or less expensive than the isx counterpart. ask me and i can pretty much tell you what a part will cost, as i have a d12d and my good friend runs an isx. i can tell you he has spent more on his engine than i have mine. (he says he got a monday engine)

as far as fuel mileage reports from a company driver go i would discount them as false, because we all know company drivers run with their right foot on the floor all of the time!

 

isx problems......egr, turbo control valve, exhaust and intake gaskets, oil coolers, did i mention egr valve (two to one on ved12) fuel pressure regulator, main wiring harness is routed wrong from factory and if you haven't had it rerouted you will have problems with it shorting to the block.

d12d problems with 781k two egr valves, leveling valve rear, udated leveling valves in the front(to two valve system) fan control selenoid, thermostat at 720K , 95% or better compression in all cyl., ave 6.6mpg (have egr system blocked) all miles. honestly i can't complain too much, except to say that i wish the torque was a little better.