I heard something about Delphi 1 and Delphi 2 QS. What is the deference and when was the change made? I'm looking to buy a 1500HD/2500LD and I want to make the best decision I can.

2005 was the last year, and is said to be the best year, but I haven't heard of Delphi 1 and Delphi 2, other than what another poster asked about in this same forum a few posts ago.

So is there a big difference between the 2003-2005? Is the 03 still a great system or should I hold out and pay more for an 04 or 05?

No, get any 03, 04, or 05.

The benefits of the 05 are more horsepower and torque, an upgraded alternator charging system, and other things which have nothing to do with 4WS.

As far as 4WS differences in 05 go, the most significant one is the lack of a monitoring module that, if it fails for some reason, causes fault codes that revert 4WS back to 2WS and necessitate a dealership visit.

The module is called a Yaw Sensor and Lateral Accelerometer. It is usually located under the passenger seat, and is the same module that vehicles with Stabilitrak use. But 4WS trucks do not have Stabilitrak, so the module is uneeded otherwise.

When Quadrasteer first came out, this module was installed as a monitoring module... to allow engineers to know what the yaw rate and lateral acceleration rate (skid) was on the data recorder.

In 2003 and 2004, the module's outputs did not effect or inform the function of the 4WS, however, if the module had unexpected values or did not communicate back through the Class 2 data bus, the Rear Wheel Steering Module would cry foul and send error codes to the DIC.

In 2005, since the module wasn't being used to control the function of 4WS... only to monitor the vehicle, the module was deleted to save money. Kevin L, of Delphi, stated that the 4WS system was "overengineered", and that his team looked for ways to thrift out unecessary parts to the system.

The fewer electronic gizmo's, the less potential for gremlins and faults, the more reliable the system is, presumably.

However, some 2005 versions had other parts thrifted out as well. Paint, for one. The 4WS module used to be painted black, but since the module is cast from metals that do not rust (aluminum or magnesium, not sure which), they stopped painting them. Saved a few bucks.

Also, some 2005 versions no longer have a little skidplate. Two schools of thought there. One is that the skidplate should be there to take the hit instead of the steering housing. The other is that the presence of the skidplate lowers the ground clearance by almost an 1", making it more likely for the axle to strike an object that it would otherwise clear.

As for Version 1 and Version 2, the only thing I can think of is that in the truck engineering heydays of 2000 through 2003, plans were drawn up to create an independent rear suspension version of Quadrasteer. Prototypes were built that also incorporated the function of ABS brakes, such that the rear axle not only steered independently and was suspeneded independently, it braked independently in cooperation with these other movements for the ultimate in stability and skid control and automatic corrections. That was to be the next generation of Quadrasteer, or version 2 as you called it.

That never came to be.

Thanks, Quadrafacts, for the excellent discussion of the evolution of the QS system. Great as QS is in the up-to-2005 GM light trucks, the IRS+ system you describe would be soooo much more appealing, not only in trucks but in some of the 500-600-and-up bhp supercars that have appeared recently. Sad that GM so mis-marketed QS that Delphi never saw the revenue stream that would have supported this next evolution.

Just curious, is there a reason you're ignoring '02?

Thanks for the great info. If anyone knows of a qs crew cab for sale (preferably in the south/no chassis rust) let me know. Also, Top Dog, I was only leaving 02 out because I am looking for the crew cab and they were only available 03-05.

KONG...

Haven't heard from you in ages. I remember you as being the one to appreciate the near 50/50 weight ratio of your QS Sub, and the one who widened your wheels/tires for the summer, but carefully stayed with the exact same diameter as stock. You were/are all about sports car handling.

What do you think of the Challenger chassis?

Hi, Quadrafacts. Yes, I've not been active on this site for a while, but do see notifications of postings and join in where I have something to say.

Yes, no question that much of my enthisiasm for the QS package on the Sub is the shockingly crisp handling, better than the vaunted Z71 wimp or any other variant of Sub I've tried.

The rear steering is responsible for part of that, but the 4" wider rear track (which in turn probably is mostly there to accomodate the mechanism to allow the wheels to steer) and the significant rear camber (which I'm guessing is there mostly because our friends at Delphi are serious motorheads) are at least as useful.

The only Challenger I know at the moment is the revived muscle coupe from Dodge, whose rear-drive, front-steer chassis is basically that of the Chrysler 300 and Dodge Charger. Please tell me about the Challenger you have in mind.